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Effects of Fresh Watermelon Consumption on the Acute Satiety Response and Cardiometabolic Risk Factors in Overweight and Obese Adults

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Although some studies have demonstrated the beneficial effects of watermelon supplementation on metabolic diseases, no study has explored the potential mechanism by which watermelon consumption improves body weight management. The objective of this study was to evaluate the effects of fresh watermelon consumption on satiety, postprandial glucose and insulin response, and adiposity and body weight change after 4 weeks of intervention in overweight and obese adults. In a crossover design, 33 overweight or obese subjects consumed watermelon (2 cups) or isocaloric low-fat cookies daily for 4 weeks. Relative to cookies, watermelon elicited more (p < 0.05) robust satiety responses (lower hunger, prospective food consumption and desire to eat and greater fullness). Watermelon consumption significantly decreased body weight, body mass index (BMI), systolic blood pressure and waist-to-hip ratio (p ≤ 0.05). Cookie consumption significantly increased blood pressure and body fat (p < 0.05). Oxidative stress was lower at four week of watermelon intervention compared to cookie intervention (p = 0.034). Total antioxidant capacity increased with watermelon consumption (p = 0.003) in blood. This study shows that reductions in body weight, body mass index (BMI), and blood pressure can be achieved through daily consumption of watermelon, which also improves some factors associated with overweight and obesity (clinicaltrials.gov, NCT03380221).
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nutrients
Article
Effects of Fresh Watermelon Consumption on the
Acute Satiety Response and Cardiometabolic Risk
Factors in Overweight and Obese Adults
Tiffany Lum, Megan Connolly, Amanda Marx, Joshua Beidler, Shirin Hooshmand, Mark Kern,
Changqi Liu and Mee Young Hong *
School of Exercise and Nutritional Sciences, San Diego State University, San Diego, CA 92182, USA;
tiffanynlum@gmail.com (T.L.); megcconnolly@gmail.com (M.C.); amandamarx27@gmail.com (A.M.);
beidler@gmail.com (J.B.); shooshmand@sdsu.edu (S.H.); kern@sdsu.edu (M.K.); changqi.liu@sdsu.edu (C.L.)
*Correspondence: mhong2@sdsu.edu; Tel.: +1-619-594-2392
Received: 11 February 2019; Accepted: 6 March 2019; Published: 12 March 2019


Abstract:
Although some studies have demonstrated the beneficial effects of watermelon
supplementation on metabolic diseases, no study has explored the potential mechanism by which
watermelon consumption improves body weight management. The objective of this study was to
evaluate the effects of fresh watermelon consumption on satiety, postprandial glucose and insulin
response, and adiposity and body weight change after 4 weeks of intervention in overweight and
obese adults. In a crossover design, 33 overweight or obese subjects consumed watermelon (2 cups)
or isocaloric low-fat cookies daily for 4 weeks. Relative to cookies, watermelon elicited more
(p< 0.05) robust satiety responses (lower hunger, prospective food consumption and desire to
eat and greater fullness). Watermelon consumption significantly decreased body weight, body
mass index (BMI), systolic blood pressure and waist-to-hip ratio (p
0.05). Cookie consumption
significantly increased blood pressure and body fat (p< 0.05). Oxidative stress was lower at four
week of watermelon intervention compared to cookie intervention (p= 0.034). Total antioxidant
capacity increased with watermelon consumption (p= 0.003) in blood. This study shows that
reductions in body weight, body mass index (BMI), and blood pressure can be achieved through
daily consumption of watermelon, which also improves some factors associated with overweight
and obesity (clinicaltrials.gov, NCT03380221).
Keywords: watermelon; satiety; oxidative stress; antioxidant; human
1. Introduction
Obesity, which affects 39.8% of U.S. adults, contributes to numerous health problems, including
cardiovascular disease, hypertension, type II diabetes, and other leading causes of mortality [
1
,
2
].
Common treatments for obesity include medications and diets that restrict total calories or specific
macronutrients. However, obesity medications are associated with adverse effects, and only about
one-fifth of dieters maintain their weight loss for at least one year [
3
,
4
]. In light of the serious health
consequences of obesity and the limited success of current therapies, there is an urgent need for
new approaches.
Healthful snacking may be a simpler and more sustainable approach to improving dietary quality,
increasing satiety, and combating weight gain. Over a 40-year period, self-reported eating behaviors of
adults demonstrated increased energy intake when snacks were consumed between lunch and dinner
or eaten in place of meals [
5
]. Therefore, choosing snacks that are lower in calories could contribute to
a significant reduction in total energy intake. As a snack, fruit is palatable and convenient, and has
Nutrients 2019,11, 595; doi:10.3390/nu11030595 www.mdpi.com/journal/nutrients
Nutrients 2019,11, 595 2 of 13
generally been associated with lower body weight in epidemiological studies [
6
]. The tendency of fruit
to promote a healthy body weight may result from its high water and fiber content, which results in a
lower energy density compared with many other popular snack foods [
7
]. Because people tend to eat a
consistent weight of food during a meal or snack, selecting foods that are lower in energy density can
lead to greater satiety and lower total energy intake [7].
Fruit has been associated with greater satiety [
8
10
] and lower subsequent energy intake [
9
11
]
compared with refined carbohydrate snacks. Although the effects of watermelon on satiety and body
weight have not been investigated, watermelon is a strong candidate to promote satiety because its
high water content results in a lower energy density than most fruits. One cup of diced watermelon
contains only 46 kilocalories but meets 21% of the daily requirement for vitamin C and 17% of the
daily requirement for vitamin A [
12
]. In addition to aiding in weight management, fruit snacks can
improve diet quality [
13
]. Replacing conventional snack foods with watermelon could increase intake
of potassium and dietary fiber, which are under-consumed, while reducing intake of added sugars
and saturated and trans fats, which are consumed in excess [
14
]. Watermelon has been described as a
functional food due to its possible health benefits [
15
]. Red-fleshed watermelon varieties are rich in
lycopene, a carotenoid that may protect against cancer and cardiovascular disease [
16
]. Watermelon is
also the richest food source of L-citrulline, a non-essential amino acid that functions as a precursor
for nitric oxide synthesis [
17
]. Watermelon consumption has been linked to lower blood pressure in
humans [17] and improved blood lipid profile in animals and humans [1821].
The purpose of this study was to compare the effects of watermelon and an isocaloric
low-fat cookie snack on body weight, appetitive sensations, postprandial glucose and insulin,
and appetite-regulating hormone concentrations. To determine the effects of chronic watermelon
consumption, physiological and metabolic outcomes were measured before and after four weeks of the
two snacks. Additionally, acute effects were determined by measuring perceived appetite sensations
and blood concentrations of glucose, insulin, and appetite-regulating hormones before and up to
120 min after consumption of the two snacks. We hypothesized that watermelon consumption would
reduce body weight by increasing perceived satiety and moderating postprandial glucose and insulin
responses compared with an isocaloric low-fat cookie snack.
2. Materials and Methods
2.1. Participants
Overweight and obese adults (males n= 20, females n= 13) between the ages of 18 and 55 years
with a body mass index (BMI) of 25–40 kg/m
2
were recruited in Southern California. Exclusion criteria
included pregnancy, smoking, any medical problems or metabolic disorders that might alter appetite
or body weight, and allergies to or dislike of watermelon (WM) or any ingredient in low-fat cookies
(LFC) such as gluten, milk protein, and eggs. Individuals who were actively dieting or engaged in
weight loss activities were also excluded, as were women with irregular menstrual cycles. The study
was approved by the San Diego State University Institutional Review Board. Potential participants
were screened for eligibility criteria, and informed written consent was obtained (clinicaltrials.gov,
NCT03380221).
2.2. Study Design
This study utilized a crossover design with two 4-week dietary interventions separated by
a 2–4 week washout period to prevent carryover effects. Based on a previous human trial of
watermelon [
22
], power analysis (G*Power, Germany) indicated that significant differences would be
detected with a sample of 33 subjects at 75% power and an alpha-level of p< 0.05. Eligible participants
(n= 33) were assigned to a 4-week repeated measures crossover with two treatments given—a WM
snack followed by a 2–4 week washout period, and then crossed over to an isocaloric-matched LFC
snack. Subjects visited the lab at baseline and after 4 weeks for each intervention. Female participants
Nutrients 2019,11, 595 3 of 13
started each trial at day 3 to 11 of their menstrual cycles. Visits occurred in the morning after a 10-h
overnight fast. Height and weight (Detecto weigh beam eye-level; Webb City, MO, USA), body fat
(dual-energy X-ray absorptiometry, Prodigy, GE Healthcare, Chicago, IL, USA), waist circumference,
hip circumference, and blood pressure (Omron M3; Kyoto, Japan) were assessed for each visit.
During the baseline visits, each subject was instructed on completion of a visual analogue scale
(VAS) to assess baseline appetite [
23
]. Blood samples were collected, then subjects were instructed to
consume 2 cups of fresh WM (92 kcal) or isocaloric LFC (92 kcal, Nilla Wafers Reduced Fat, Nabisco,
East Hanover, NJ, USA) along with 8 fl. Oz of water in the laboratory. Postprandial responses
were measured by administering new VAS to subjects at 20, 40, 60, 90, and 120 min following snack
consumption. A second blood sample was collected 60 min post-snack consumption. Blood samples
were centrifuged at 1200
×
gfor 10 min at 4
C and serum samples were stored at
80
C until analysis.
During the WM intervention, participants consumed 2 cups of fresh diced WM (92 kcal) daily for
4 weeks. During the LFC intervention, participants consumed Nabisco vanilla wafer cookies (92 kcal)
daily for 4 weeks. Each WM serving contained 92 kcal, 23 g carbohydrate, 2 g protein, 0 g fat, and 1 g
fiber. Each LFC serving contained 92 kcal, 18.2 g carbohydrate, 0.76 g protein, 1.14 g fat, and 0 g fiber.
Participants could consume their snacks at any time of day, during one or multiple sittings, alone or in
combination with other foods in order to resemble snacking conditions in everyday life. Participants
were asked to avoid consuming LFC during the WM intervention and to avoid consuming WM during
the LFC intervention, in order to keep the potential effects of the two snacks separate. Aside from
the daily consumption of either snack, participants were instructed to maintain their typical dietary
intakes and physical activity levels. At the end of each four-week intervention, fasting blood samples
were collected.
2.3. Satiety Questionnaire
The visual analogue scale (VAS) [
23
] measured appetite responses by asking a series of 5 questions
assessing hunger, fullness, desire to eat, prospective food consumption, and thirst. Each question was
followed by a 10 cm line with words anchored at each end, expressing the lowest (0 cm) and highest
(10 cm) ratings of each. Subjects could record their responses by marking a spot on the line indicating
their feelings about each question. Responses were quantified by measuring the distance from the left
end of the line to the designated mark.
2.4. Dietary Assessment and Physical Activity
Dietary intake was measured using 24-h dietary recalls on the two days preceding the in-laboratory
visit by trained staff. The United States Department of Agriculture (USDA) Supertracker (2012) was
used to evaluate average daily energy intakes. Physical activity levels were also assessed using a
validated Physical Activity Recall (PAR) Questionnaire [24].
2.5. Postprandial Glucose and Insulin Response
Serum glucose was measured using a colorimetric glucose assay kit (Stanbio Laboratory, Boerne,
TX, USA) and analyzed according to the manufacturer’s instructions. A reagent containing glucose
oxidase was mixed with the serum samples in cuvettes, resulting in the formation of hydrogen
peroxide. The hydrogen peroxide then reacted to form a quinone complex. The absorbance of the
quinone complex was read at 500 nm.
Insulin was measured with a sandwich enzyme-linked immunosorbent assay (ELISA) kit (ALPCO,
Salem, NH, USA). The serum samples and secondary antibody were added to the insulin-specific
antibody coated wells. A 3,3
0
,5,5
0
-tetramethylbenzidine (TMB) substrate was added to the wells to
produce color and the plates were incubated a second time. Lastly, a stop solution was added and the
plates were measured spectrophotometrically at 450 nm.
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2.6. Appetite-Regulating Hormones
The appetite-regulating hormones leptin, ghrelin, adiponectin, and cholecystokinin (CCK) were
assayed using ELISA kits (RayBiotech, Norcross, GA, USA). In each assay, the target hormone in the
samples was bound by immobilized antibodies. A biotinylated antibody was added, followed by
horseradish peroxidase-conjugated streptavidin, and finally a substrate solution that developed color
in proportion to the amount of hormone bound. Following the addition of stop solution, the plates
were measured spectrophotometrically at 450 nm.
2.7. C-Reactive Protein
C-reactive protein (CRP) was measured using an ELISA kit (Calbiotech, Spring Valley, CA, USA)
and analyzed per the manufacturer’s instructions. Microplates were coated with monoclonal antibodies
to CRP. The serum samples and anti-CRP-horseradish-peroxidase conjugated secondary antibody were
added to the microplate wells. TMB substrate was added to produce color. The plates were incubated,
stop solution was added, and absorbance was measured at 450 nm.
2.8. Serum Lipids
Blood lipid profiles were analyzed using serum triglyceride (TG), total cholesterol (TC) and
high-density lipoprotein cholesterol (HDL-C) (Stanbio Laboratory, Boerne, TX, USA) colorimetric assay
kits. Low-density lipoprotein cholesterol (LDL-C) was calculated using the following equation: LDL
cholesterol = total cholesterol HDL cholesterol (triglycerides/5) [25].
2.9. Thiobarbituric Acid Reactive Substances (TBARS)
Lipid peroxidation as a marker of oxidative stress was analyzed using a thiobarbituric acid
reactive substances (TBARS) assay kit (Cayman Chemical Company, Ann Arbor, MI, USA). The assay
standards were prepared with malondialdehyde. The standards and serum samples were mixed with
sodium dodecyl sulfate solution in vials, then the thiobarbituric acid was added. Vials were boiled
for 1 h, and then placed in an ice bath. Samples were centrifuged and pipetted into microplate wells.
Absorbance was measured at 535 nm.
2.10. Catalase Activity
Catalase activity, a marker of antioxidant capacity, was analyzed using a catalase assay kit
(Cayman Chemical Company). Serum samples were mixed with hydrogen peroxide to initiate the
formation of formaldehyde. Potassium hydroxide was added to stop the reaction and chromogen was
added for colorimetric measurement of formaldehyde production. Catalase potassium periodate was
added, then absorbance was read at 540 nm.
2.11. Total Antioxidant Capacity
Total antioxidant capacity (TAC) was analyzed using an antioxidant assay kit (Cayman Chemical
Company). Standards were prepared using Trolox. The standards and serum samples were
mixed with metmyoglobin and chromogen and then hydrogen peroxide was added to initiate the
reactions. Inhibition of the oxidation of 2,20-Azino-di-(3-ethylbenzothiazoline sulphonate) (ABTS) by
metmyoglobin was measured by reading the absorbance at 405 nm using a spectrophotometer.
2.12. Liver Function Markers
Alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST),
creatine kinase (CK), and lactate dehydrogenase (LDH) were determined in serum samples using
assay kits from Stanbio (Boerne, TX, USA). All assays were performed according to the manufacturer’s
instructions. ALP was read at 405 nm and the other enzyme assays were read at 340 nm.
Nutrients 2019,11, 595 5 of 13
2.13. Statistical Analysis
The normality of the data was checked using the explore function in SPSS (SPSS Statistics version
24, IBM, Armonk, NY, USA). When data showed a normal distribution, two-way repeated measures
ANOVA were used to analyze the effects of WM and LFC treatments on each of the variables over time,
as well as any significant interactions between snack type and time. If the interaction was significant,
a least significant difference (LSD) analysis was used for post-hoc comparison. When normality
assumption was suspect, a nonparametric Wilcoxon analysis was performed. Data were considered
statistically significant when p< 0.05.
3. Results
3.1. Body Weight and Blood Pressure
Significant interactions were found for body weight (Interaction p= 0.005; Snack effect p= 0.064;
Time effect p= 0.730) and BMI (Interaction p= 0.006; Snack effect p= 0.061; Time effect p= 0.799). Body
weight and BMI values did not differ significantly between the two interventions at baseline, but were
significantly lower after four weeks of WM consumption and significantly higher after four weeks
of LFC consumption compared with baseline values (Table 1). Four weeks of WM consumption did
not change systolic blood pressure (SBP) and diastolic blood pressure (DBP), but four weeks of LFC
consumption significantly increased both SBP (p= 0.015) and DBP (p= 0.001). Waist-to-hip ratio was
lowered at week four of WM consumption compared with week for of LFC consumption (p= 0.019).
Body fat percentage did not change significantly over the course of the WM intervention but was
significantly higher at week four of the LFC intervention than at baseline (p= 0.005). Dietary intake of
total energy, carbohydrate, protein, fat and dietary fiber, and moderate and hard physical activity were
not different between the trials.
Table 1.
Effects of snacks on body weight, body mass index (BMI), blood pressure, waist-to-hip ratio,
and body fat of participants at baseline and week 4 for each intervention.
Measurements Watermelon (n= 33) Cookies (n= 33)
Baseline Week 4 Baseline Week 4
Body Weight (kg) 89.4 ±15 a88.9 ±16 b89.3 ±16 a89.9 ±16 c
BMI 30.5 ±3.5 a30.4 ±3.7 b30.5 ±3.7 a30.7 ±3.8 c
SBP (mm Hg) 127 ±15 a,b 125 ±14 a124 ±14 a129 ±14 b
DBP (mm Hg) 79.9 ±7.2 a79.6 ±9.7 a77.2 ±9.0b81.2 ±10 a
W/H ratio 0.850 ±0.06 a,b 0.845 ±0.07 a0.847 ±0.07 a,b 0.857 ±0.07 b
Body Fat (%) 37.8 ±8.2 a38.0 ±8.5 a37.7 ±8.2 a38.2 ±7.9 b
Data are presented as means
±
SD. Data within rows with varying superscript letters are statistically different
(p< 0.05). n= 33 (20 males/13 females). BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood
pressure; W/H ratio, waist-to-hip ratio.
3.2. Appetite
The VAS response curves for hunger, fullness, desire to eat, prospective food consumption, and
thirst are presented in Figure 1for both WM and LFC snacks. For hunger, WM produced lower ratings
of hunger for up to 90-min post-consumption compared with baseline, while LFC significantly reduced
hunger for only up to 20-min post-consumption (Figure 1A). Feelings of hunger were significantly
greater for LFC compared with WM at 20, 40, 60, and 90 min (p< 0.05) (Figure 1a). Participants were
significantly more full between baseline and 90-min for WM, and from baseline to 40-min for LFC
(Figure 1b). Feelings of fullness were significantly greater for WM compared with LFC from 20-min to
90-min post-consumption (p< 0.05) (Figure 1b). Compared with baseline, desire to eat was significantly
reduced up to 90-min post-WM consumption, while LFC only reduced the desire to eat for up to 20-min
post-consumption (Figure 1c). Desire to eat was significantly greater for LFC compared with WM at
Nutrients 2019,11, 595 6 of 13
all time points after consumption of snacks (p< 0.05) (Figure 1c). Similar to desire to eat, prospective
food consumption was significantly reduced for up to 90-min post-WM consumption compared with
baseline, while there were no differences for the LFC at any of the time points (Figure 1d). Prospective
food consumption significantly differed between snacks up to 90-min post-consumption (p< 0.05)
(Figure 1d). Thirst was significantly reduced at 20-min compared with baseline for both WM and
LFC, while feelings of thirst were significantly reduced after WM consumption compared with LFC
consumption at 20 and 40-mins (p< 0.05) (Figure 1e).
Nutrients 2019, 11, x FOR PEER REVIEW 6 of 13
baseline for both WM and LFC, while feelings of thirst were significantly reduced after WM
consumption compared with LFC consumption at 20 and 40-mins (p < 0.05) (Figure 1e).
(a)
(b)
(d)
(e)
Figure 1. Effects of watermelon (WM) and low-fat cookies (LFC) on (a) hunger, (b) fullness, (c) desire
to eat, (d) prospective food consumption, and (e) thirst. *: different between WM and LFC; +: different
from baseline. VAS: visual analogue scale.
3.3. Glucose and Insulin
No significant differences in blood glucose concentrations were found between snacks at
baseline or at 1-h postconsumption. Furthermore, there was no change in blood glucose at 1-h
postconsumption compared with baseline for either snack (Figure 2a). Blood insulin levels
significantly increased for both snacks 1-h postconsumption compared with baseline (p < 0.05), but
no significant differences were found between snacks (Figure 2b). Following the four-week
interventions, serum glucose levels were not significantly different between the WM and LFC
interventions. There were also no significant changes in serum glucose between baseline (5.10 ± 1.36
mmol/L vs. 5.20 ± 1.20 mmol/L) and week four (5.59 ± 1.90 mmol/L vs. 5.10 ± 0.90 mmol/L) within
each intervention. Similarly, serum insulin levels were not significantly different between the WM
and LFC interventions at baseline (25.4 ± 2.1 mIU/L vs. 27.4 ± 1.8 mIU/L) or week four (27.5 ± 2.0
mIU/L vs. 26.8 ± 2.0 mIU/L) and did not change significantly from baseline to week four within each
intervention.
Figure 1. Effects of watermelon (WM) and low-fat cookies (LFC) on (a) hunger, (b) fullness, (c) desire
to eat, (
d
) prospective food consumption, and (
e
) thirst. *: different between WM and LFC; +: different
from baseline. VAS: visual analogue scale.
3.3. Glucose and Insulin
No significant differences in blood glucose concentrations were found between snacks at baseline
or at 1-h postconsumption. Furthermore, there was no change in blood glucose at 1-h postconsumption
compared with baseline for either snack (Figure 2a). Blood insulin levels significantly increased for
both snacks 1-h postconsumption compared with baseline (p< 0.05), but no significant differences
were found between snacks (Figure 2b). Following the four-week interventions, serum glucose levels
were not significantly different between the WM and LFC interventions. There were also no significant
changes in serum glucose between baseline (5.10
±
1.36 mmol/L vs. 5.20
±
1.20 mmol/L) and
week four (5.59
±
1.90 mmol/L vs. 5.10
±
0.90 mmol/L) within each intervention. Similarly, serum
insulin levels were not significantly different between the WM and LFC interventions at baseline
(25.4
±
2.1 mIU/L vs. 27.4
±
1.8 mIU/L) or week four (27.5
±
2.0 mIU/L vs. 26.8
±
2.0 mIU/L) and
did not change significantly from baseline to week four within each intervention.
Nutrients 2019,11, 595 7 of 13
Nutrients 2019, 11, x FOR PEER REVIEW 7 of 13
(a)
(b)
Figure 2. (a) Effects of WM and LFC on postprandial glucose. No significant differences in blood
glucose were observed between snacks and between pre-consumption (pre) and 1-h postconsumption
(post). (b) Effects of WM and LFC on postprandial insulin. Blood insulin significantly increased (p <
0.05) in both snacks 1-h postconsumption compared with baseline. Data are presented as means ± SD.
Within a variable, values not sharing common superscript are significantly different at p < 0.05.
3.4. Appetite-Regulating Hormones
The appetite-regulating hormones leptin, ghrelin, adiponectin, and CCK were measured in
blood samples taken at the baseline fasted state and 1-h after snack consumption (Table 2). WM
reduced leptin levels (p = 0.017), and LFC showed a trend to reduce leptin (p = 0.057). WM resulted
in higher ghrelin (p = 0.004), and LFC tended to increase ghrelin levels (p = 0.086). There was a trend
toward higher adiponectin concentration after WM consumption (p = 0.055).
Table 2. Effects of WM or LFC consumption on postprandial satiety hormone.
Watermelon (n = 33)
Cookies (n = 33)
Pre
Post
Pre
Post
Leptin (ng/mL)
3.65 ± 2.02 a
3.28 ± 2.01 b
3.71 ± 1.96 a
3.42 ± 2.07 a,b
Ghrelin (pg/mL)
414 ± 246 a
520 ± 356 b
424 ± 250 a
511 ± 352 a,b
Adiponectin (ug/mL)
9.93 ± 5.81
10.66 ± 5.08
9.20 ± 5.63
8.41 ± 6.33
CCK (pg/mL)
465 ± 242
514 ± 170
495 ± 178
542 ± 207
Values are means ± SD. n = 33 (20 males/13 females).
3.5. C-Reactive Protein
Serum CRP as an indicator of chronic inflammation was not significantly different between the
WM and LFC interventions at baseline (7.21 ± 3.37 mg/L vs. 7.14 ± 2.94 mg/L) or week four (7.07 ±
3.18 mg/L vs. 7.19 ± 3.36 mg/L) and did not differ significantly over time within each intervention.
3.6. Serum Lipids
Lipid profiles are shown below in Figure 3. WM consumption significantly lowered TG (p =
0.046). TC was significantly lower after four weeks of the WM intervention compared with LFC (p =
0.024). WM consumption significantly increased HDL-C (p = 0.046), while there was a trend toward
lower HDL-C following LFC consumption (p = 0.066). LDL cholesterol decreased significantly after
four weeks of WM consumption and increased significantly after four weeks of LFC consumption (p
= 0.011).
0
1
2
3
4
5
6
Watermelon Cookies
Glucose (mmol/L)
Baseline Week 4
0
20
40
60
80
100
Watermelon Cookies
Insulin (µIU/mL)
a
b
a
b
Baseline Week 4
Figure 2.
(
a
) Effects of WM and LFC on postprandial glucose. No significant differences in blood
glucose were observed between snacks and between pre-consumption (pre) and 1-h postconsumption
(post). (
b
) Effects of WM and LFC on postprandial insulin. Blood insulin significantly increased
(p< 0.05) in both snacks 1-h postconsumption compared with baseline. Data are presented as
means
±
SD. Within a variable, values not sharing common superscript are significantly different at
p< 0.05.
3.4. Appetite-Regulating Hormones
The appetite-regulating hormones leptin, ghrelin, adiponectin, and CCK were measured in blood
samples taken at the baseline fasted state and 1-h after snack consumption (Table 2). WM reduced
leptin levels (p= 0.017), and LFC showed a trend to reduce leptin (p= 0.057). WM resulted in higher
ghrelin (p= 0.004), and LFC tended to increase ghrelin levels (p= 0.086). There was a trend toward
higher adiponectin concentration after WM consumption (p= 0.055).
Table 2. Effects of WM or LFC consumption on postprandial satiety hormone.
Watermelon (n= 33) Cookies (n= 33)
Pre Post Pre Post
Leptin (ng/mL) 3.65 ±2.02 a3.28 ±2.01 b3.71 ±1.96 a3.42 ±2.07 a,b
Ghrelin (pg/mL) 414 ±246 a520 ±356 b424 ±250 a511 ±352 a,b
Adiponectin (µg/mL) 9.93 ±5.81 10.66 ±5.08 9.20 ±5.63 8.41 ±6.33
CCK (pg/mL) 465 ±242 514 ±170 495 ±178 542 ±207
Values are means ±SD. n= 33 (20 males/13 females).
3.5. C-Reactive Protein
Serum CRP as an indicator of chronic inflammation was not significantly different between
the WM and LFC interventions at baseline (7.21
±
3.37 mg/L vs. 7.14
±
2.94 mg/L) or week
four (7.07
±
3.18 mg/L vs. 7.19
±
3.36 mg/L) and did not differ significantly over time within
each intervention.
3.6. Serum Lipids
Lipid profiles are shown below in Figure 3. WM consumption significantly lowered TG (p= 0.046).
TC was significantly lower after four weeks of the WM intervention compared with LFC (p= 0.024).
WM consumption significantly increased HDL-C (p= 0.046), while there was a trend toward lower
HDL-C following LFC consumption (p= 0.066). LDL cholesterol decreased significantly after four
weeks of WM consumption and increased significantly after four weeks of LFC consumption (p= 0.011).
Nutrients 2019,11, 595 8 of 13
Nutrients 2019, 11, x FOR PEER REVIEW 8 of 13
Figure 3. Effects of WM and LFC on serum concentrations of triglycerides (TG), total cholesterol (TC),
high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) at
baseline and week 4 of each intervention. Data are presented as means ± SD. Within a variable, values
not sharing a common superscript are significantly different at p < 0.05.
3.7. Oxidative Stress and Antioxidant Capacity
After four weeks of WM treatment, there was a trend toward lower TBARS, an indicator of lipid
peroxidation (p = 0.091). The LFC intervention showed a trend toward higher lipid peroxidation from
baseline to week four (p = 0.092) (Figure 4a). Lipid peroxidation was lower at four week of WM
intervention compared to four weeks of LFC intervention (p = 0.034). Levels of catalase, an antioxidant
enzyme, were not significantly different between the two interventions. Total antioxidant capacity
did not change significantly after four weeks of LFC consumption but increased significantly after
four weeks of WM consumption (p = 0.003) (Figure 4b).
(a)
(b)
Figure 4. Effects of WM and LFC on serum values for (a) thiobarbituric acid reactive substances
(TBARS) and (b) total antioxidant capacity (TAC) at baseline and week 4 of each intervention. Data
are presented as means ± SD. Within a variable, values not sharing a common superscript are
significantly different at p < 0.05.
0
1
2
3
4
5
6
TG TC HDL-C LDL-C
Concentration (mmol/L)
Watermelon Baseline
Watermelon Week 4
Cookies Baseline
Cookies Week 4
abaaaba,b a
aba
c
aaab
0
5
10
15
Watermelon Cookies
TBARS (umol/L)
Baseline Week 4
ab
aab
b
0
1
2
3
4
Watermelon Cookies
TAC (mmol/L)
a
bbb
Baseline Week 4
Figure 3.
Effects of WM and LFC on serum concentrations of triglycerides (TG), total cholesterol (TC),
high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) at
baseline and week 4 of each intervention. Data are presented as means
±
SD. Within a variable, values
not sharing a common superscript are significantly different at p< 0.05.
3.7. Oxidative Stress and Antioxidant Capacity
After four weeks of WM treatment, there was a trend toward lower TBARS, an indicator of lipid
peroxidation (p= 0.091). The LFC intervention showed a trend toward higher lipid peroxidation
from baseline to week four (p= 0.092) (Figure 4a). Lipid peroxidation was lower at four week of WM
intervention compared to four weeks of LFC intervention (p= 0.034). Levels of catalase, an antioxidant
enzyme, were not significantly different between the two interventions. Total antioxidant capacity did
not change significantly after four weeks of LFC consumption but increased significantly after four
weeks of WM consumption (p= 0.003) (Figure 4b).
Nutrients 2019, 11, x FOR PEER REVIEW 8 of 13
Figure 3. Effects of WM and LFC on serum concentrations of triglycerides (TG), total cholesterol (TC),
high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) at
baseline and week 4 of each intervention. Data are presented as means ± SD. Within a variable, values
not sharing a common superscript are significantly different at p < 0.05.
3.7. Oxidative Stress and Antioxidant Capacity
After four weeks of WM treatment, there was a trend toward lower TBARS, an indicator of lipid
peroxidation (p = 0.091). The LFC intervention showed a trend toward higher lipid peroxidation from
baseline to week four (p = 0.092) (Figure 4a). Lipid peroxidation was lower at four week of WM
intervention compared to four weeks of LFC intervention (p = 0.034). Levels of catalase, an antioxidant
enzyme, were not significantly different between the two interventions. Total antioxidant capacity
did not change significantly after four weeks of LFC consumption but increased significantly after
four weeks of WM consumption (p = 0.003) (Figure 4b).
(a)
(b)
Figure 4. Effects of WM and LFC on serum values for (a) thiobarbituric acid reactive substances
(TBARS) and (b) total antioxidant capacity (TAC) at baseline and week 4 of each intervention. Data
are presented as means ± SD. Within a variable, values not sharing a common superscript are
significantly different at p < 0.05.
0
1
2
3
4
5
6
TG TC HDL-C LDL-C
Concentration (mmol/L)
Watermelon Baseline
Watermelon Week 4
Cookies Baseline
Cookies Week 4
abaaaba,b a
aba
c
aaab
0
5
10
15
Watermelon Cookies
TBARS (umol/L)
Baseline Week 4
ab
aab
b
0
1
2
3
4
Watermelon Cookies
TAC (mmol/L)
a
bbb
Baseline Week 4
Figure 4.
Effects of WM and LFC on serum values for (
a
) thiobarbituric acid reactive substances
(TBARS) and (
b
) total antioxidant capacity (TAC) at baseline and week 4 of each intervention. Data are
presented as means
±
SD. Within a variable, values not sharing a common superscript are significantly
different at p< 0.05.
Nutrients 2019,11, 595 9 of 13
3.8. Liver Function Markers
There were no significant differences in the liver function markers AST, ALT, ALP, LDH, or CK
after four weeks of the WM and LFC interventions.
4. Discussion and Conclusions
As a natural food that provides fiber, micronutrients, and bioactive phytochemicals, watermelon
may be a healthier alternative to conventional snacks. This study compared the effects of consuming
watermelon versus an isocaloric low-fat cookie snack for four weeks on body weight, blood
pressure, glucose and insulin concentrations, and biomarkers for inflammation, oxidative stress,
and liver function. In addition, the acute effects of the two snacks were determined by measuring
perceived appetite, blood glucose, insulin, and appetite-regulating hormone concentrations for up to
120 min post-consumption.
After four weeks, body weight and BMI increased in the LFC trial and decreased in the watermelon
trial. Only a few intervention studies have compared a fruit snack with a processed snack, and none
showed significant effects on body weight or other measures of adiposity [
11
,
26
,
27
]. Watermelon
consumption has been associated with reduced weight gain and fat mass in some animal studies [
18
,
28
].
In humans, however, watermelon feeding studies with a duration of up to six weeks have not reported
changes in body weight or body composition [
21
,
22
,
29
32
]. A possible explanation for these divergent
results is that prior studies used watermelon juice or reconstituted watermelon powder, whereas our
study used whole watermelon flesh. Whole fruit has been shown to promote greater satiety than
juice [
33
]. This effect could be attributed to higher fiber content, which promotes satiety and reduces
energy intake [
34
,
35
]. However, Flood-Obbagy and Rolls found that whole apples were more satiating
than apple juice or applesauce, despite having similar fiber content [
33
]. Whole fruit has greater
volume and requires more chewing than other forms, which could affect food intake by initiating
cephalic-phase responses related to digestion and metabolism [
33
]. In addition, subject expectations
that solid foods are more filling than juice may contribute to the satiating effects of whole fruit [33].
Acute watermelon consumption resulted in significantly greater satiety ratings than the LFC
snack. The watermelon snack left subjects feeling significantly less hungry compared with baseline
for up to two hours after snack consumption, while the LFC snack only reduced hunger for up to
20 min. Compared with the LFC snack, the watermelon snack had significantly greater volume due to
its high water content. The volume of food can contribute to increased satiety through such factors
as perception of the amount of food being consumed, time spent consuming food, rate of gastric
emptying, and degree of gastric distension [
36
,
37
]. The sensory and hedonic characteristics of food
such as sight, smell, texture, and taste can also influence palatability and satiety [
38
]. Appetite ratings
reflect subjective feelings of satiety, and therefore concentrations of hunger and satiety hormones
may provide better insight into the mechanisms controlling hunger and fullness. Watermelon
consumption tended to increase adiponectin, which may partially explain the higher satiety effects of
watermelon consumption.
Because the watermelon snack contained almost twice as much total sugar (17 g) as the LFC
snack (9 g), it would be expected to produce a higher postprandial glucose concentration. However,
postprandial glucose and insulin were not significantly different between the two snacks. In previous
studies, fruit produced smaller increases in blood glucose [
8
,
39
,
40
] and insulin [
8
,
39
,
41
] compared
with processed foods. Although the watermelon snack contains sugar, the total load was quite
low; therefore, the blood glucose concentrations apparently returned to normal within one hour.
Additionally, watermelon possesses other nutritional components that may have suppressed a rise in
blood glucose. Watermelon contains a small amount of dietary fiber, which can improve glucose
tolerance [
42
]. What is likely of greater importance is that more than half of the total sugars
in watermelon consist of fructose, which has little effect on blood glucose levels [
12
,
39
]. In fact,
co-ingestion of fructose and glucose blunts the glycemic response to glucose, possibly by enhancing
hepatic glucose uptake [
39
,
43
,
44
]. A meta-analysis showed that moderate intakes of up to 36 g/day
Nutrients 2019,11, 595 10 of 13
of fructose (less than the 10.3 g in two cups of watermelon) resulted in lower fasting glucose and
hemoglobin A1c (HbA1c) without causing elevated triglycerides [
45
]. Adiponectin levels were not
significantly different between the trials, although there was a trend toward increased postprandial
adiponectin following watermelon consumption. Adiponectin is a hormone secreted by adipose tissue
that is paradoxically more abundant in obese than in lean individuals, and circulating levels increase
after weight reduction [
46
,
47
]. As adiponectin increases insulin sensitivity, the trend toward increased
postprandial adiponectin following watermelon consumption may suggest a glucose-stabilizing effect.
After four weeks, the watermelon intervention showed a trend toward lower SBP compared
with baseline. In contrast, both SBP and DBP were higher after four weeks of LFC consumption.
Several previous studies have shown greater decreases in SBP and DBP with watermelon
supplementation compared with a refined carbohydrate control [
22
,
29
31
,
48
]. Watermelon is the richest
natural source of L-citrulline, a nonessential amino acid that may be responsible for watermelon’s
hypotensive effects [
17
]. L-citrulline is readily converted to L-arginine, and oral L-citrulline intake has
been shown to raise circulating L-arginine levels [
49
]. In turn, endothelial nitric oxide synthase (eNOS)
converts L-arginine to nitric oxide, which induces vascular smooth muscle relaxation [17].
Four weeks of watermelon consumption resulted in an improved blood lipid profile, including
lower levels of TG and LDL-C and higher levels of HDL-C. Following the LFC intervention, TG
and LDL-C increased and HDL-C trended lower. One prior human study showed that six weeks of
supplementation with watermelon extract reduced TC and LDL-C compared with a carbohydrate
beverage [
21
]. Several animal studies have also shown beneficial effects of watermelon consumption on
TC, LDL-C, and TG levels [
18
20
]. Analysis of hepatic mRNA expression in rats found that watermelon
reduced expression of fatty acid synthase (FAS), an enzyme involved in fatty acid synthesis, and
HMG-CoA reductase (HMGCR), the rate-limiting enzyme in cholesterol synthesis [
20
]. These metabolic
alterations may have contributed to the improved lipid profile.
Watermelon consumption for four weeks increased antioxidant status and tended to reduce
oxidative stress. One previous human study reported increased antioxidant status as indicated by
higher ferric reducing ability of plasma (FRAP) and oxygen radical absorbance capacity (ORAC)
following two weeks of watermelon supplementation [
32
]. Watermelon consumption has also been
associated with lower oxidative stress and increased antioxidant status in experimental animals [
18
20
].
These results may be partially explained by increased plasma concentrations of lycopene and other
carotenoid antioxidants [
50
,
51
]. Watermelon’s L-citrulline content may also reduce oxidative stress by
serving as a substrate for endogenous nitric oxide production [
17
]. Although nitric oxide is primarily
known for its vasodilatory properties, it can also reduce oxidative stress by scavenging or preventing
the formation of hydroxyl radicals [52].
An important limitation of this study is the measurement of postprandial response at a single
60-min time point. The current study found no significant differences in postprandial glucose or
insulin levels between trials. The protocol may have not been able to detect genuine differences if
concentrations of these biomarkers peaked before the second blood draw. In support of this hypothesis,
some studies have found glucose to peak approximately 30 min after fruit consumption and decline
thereafter [
8
,
39
]. For example, in the study by Furchner-Evanson et al., plasma glucose concentrations
did not differ significantly between the dried plum and cookie trials at the 60-min timepoint [
8
].
However, due to the higher values at the 15-, 30-, and 45-min timepoints, the cookie trial produced
a significantly higher glucose level that would not have been detected if blood would have been
collected only one hour after consumption. Future studies should include more critical time points
for measuring satiety hormones—i.e., measurements at the 15-, 30-, and 45-min marks to define
postprandial peak. Because the four-week WM trial preceded the LFC trial for all subjects, it is possible
that there was an order effect. Subjects were told that the purpose of the study was to compare effects
of different snacks on health, but they did not know that the specific focus was on watermelon versus
cookies. This aspect of the study design may have reduced the risk of the placebo or order effect.
A nested design, in which half the subjects start with watermelon and the other half with LFC, should
Nutrients 2019,11, 595 11 of 13
be used to reduce the chance of order effects in the future study. Another limitation is that it is unclear
which biochemical components or sensory qualities of watermelon contributed to increased satiety
and reduced body weight compared with the LFC control. In order to further investigate these effects,
it would be necessary to test whole watermelon against its isolated bioactive components. Finally, it is
unknown whether the watermelon dosage was optimal, or whether a larger dosage might have had
more significant effects on measured outcomes. Therefore, future studies should compare the effects of
different watermelon dosages on satiety and body weight.
In conclusion, watermelon promoted greater satiety than an isocaloric LFC snack for up to 90 min
post-consumption. Additionally, four weeks of watermelon consumption reduced body weight and
blood pressure while improving blood lipid profile and antioxidant status. These results suggest that
fresh watermelon, when consumed in place of conventional refined carbohydrate snacks, may help
reduce appetite and assist with weight management while reducing cardiovascular risk factors.
Author Contributions:
T.L., M.C., A.M., S.H., M.K. and M.Y.H. collected the data; T.L., M.C. and M.Y.H. wrote the
first draft of the manuscript; S.H., M.K., C.L. and J.B. reviewed and edited the manuscript. All authors reviewed
and commented on subsequent drafts of the manuscript.
Funding: This study was funded by the National Watermelon Promotion Board (NWPB 17-18).
Conflicts of Interest: The authors declare no conflict of interest.
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... In contrast, watermelon juice supplementation did not affect resting blood pressure in healthy postmenopausal women [9]. Furthermore, watermelon snack ingestion for four weeks did not reduce blood pressure in overweight and obese adults [68]. These findings suggest that supplementation with watermelon with at least 4 g of L-citrulline seems effective in reducing blood pressure in individuals with elevated blood pressure and hypertension, but not in normotensives. ...
... Although previous studies have demonstrated a positive effect of watermelon ingestion on arterial stiffness, AIx [2,10,65], and blood pressure [2,10,11], previous studies have not observed a significant effect of watermelon on vascular function and biomarkers [11,27,68] (Table 4). Ingestion of 2 cups of fresh diced watermelon for four weeks did not change plasma C-reactive protein (CRP) in overweight and obese adults [65]. ...
... Lum et al. [68] n = 23 (20M/13F) Overweight and obese adults Crossover In contrast, previous studies have observed a decrease in biomarkers of vascular dysfunction with synthetic L-citrulline supplementation [66,71,72]. Supplementation with 5.6 g of L-citrulline the L-arginine/ADMA ratio increased in healthy middle-aged men [66]. ...
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The amino acid L-arginine is crucial for nitric oxide (NO) synthesis, an important molecule regulating vascular tone. Considering that vascular dysfunction precedes cardiovascular disease, supplementation with precursors of NO synthesis (e.g., L-arginine) is warranted. However, supplementation of L-citrulline is recommended instead of L-arginine since most L-arginine is catabolized during its course to the endothelium. Given that L-citrulline, found mainly in watermelon, can be converted to L-arginine, watermelon supplementation seems to be effective in increasing plasma L-arginine and improving vascular function. Nonetheless, there are divergent findings when investigating the effect of watermelon supplementation on vascular function, which may be explained by the L-citrulline dose in watermelon products. In some instances, offering a sufficient amount of L-citrulline can be impaired by the greater volume (>700 mL) of watermelon needed to reach a proper dose of L-citrulline. Thus, food technology can be applied to reduce the watermelon volume and make supplementation more convenient. Therefore, this narrative review aims to discuss the current evidence showing the effects of watermelon ingestion on vascular health parameters, exploring the critical relevance of food technology for acceptable L-citrulline content in these products. Watermelon-derived L-citrulline appears as a supplementation that can improve vascular function, including arterial stiffness, endothelial function, and blood pressure. Applying food technologies to concentrate bioactive compounds in a reduced volume is warranted so that its ingestion can be more convenient, improving the adherence of those who want to ingest watermelon products daily.
... The red flesh is commonly recognized as an edible part, while the rind, seeds, and skin are discarded as by-products. Watermelon flesh shows various health benefits including its antioxidant, anti-obesity, anti-diabetic and anti-cancer effects because it contains bioactive compounds such as lycopene, β-carotene, citrulline, arginine, and phenolic compounds [8][9][10][11]. The sweetness of watermelon gives people the misconception that it causes high blood glucose levels. However, most of the sugar in watermelon is fructose which does not affect blood glucose levels and watermelon has a low glycemic load, even while it has a high glycemic index [12]. ...
... This allows people with diabetes to consume a moderate amount of watermelon. Overweight and obese adults who consumed two cups of watermelon daily for four weeks did not had increased blood glucose and insulin levels [8]. Diabetic mice fed either watermelon juice or watermelon flesh powder showed reduced fasting blood glucose levels by regulating hepatic glucose transporter and enzymes involved in glycolysis and gluconeogenesis [2,[13][14][15]. ...
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Hindering the absorption of glucose through inhibition of intestinal carbohydrate-hydrolyzing enzymes is an efficient strategy for reducing hyperglycemia. The purpose of this study was to examine the effect of watermelon flesh extracts (WFE), rind extract (WRE), skin extract (WSE), and citrulline on intestinal carbohydrate-hydrolyzing enzymes and to identify their bioactive compounds. WSE showed higher bioactive compounds and total phenolic content than WFE and WRE. WFE, WRE, and WSE demonstrated dose-dependent inhibition against carbohydrate-hydrolyzing enzymes. WFE, WRE, and WSE inhibited α-glucosidase by 40~45% at a concentration of 60 mg/mL whereas 80 mg/mL citrulline showed a similar inhibitory effect. WRE and citrulline showed IC50 values of 0.02 and 0.01 mg/mL for maltase and sucrase, respectively. Citrulline at 20 mg/mL exhibited higher glucoamylase and pancreatic α-amylase inhibition than WFE, WRE, and WSE at the same concentration. Citrulline and WRE showed similar IC50 values for glucoamylase and α-amylase compared to 1 mg/mL acarbose. This study suggests that watermelon, including its byproduct parts possibly due to citrulline, has the potential for carbohydrate-hydrolyzing enzyme inhibition that is beneficial to reducing postprandial hyperglycemia.
... As a result of its nutritional profile and allied health benefit its consumption has increased. Cancer, cardiovascular disease, diabetes, blood pressure, and obesity can all be reduced by eating watermelon [4]. As a result, the commodity's use has grown dramatically in recent years affecting people from all walks of life and socioeconomic classes. ...
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The profitability of a watermelon production diversification plan for smallholder farmers in Taraba State, Nigeria, was investigated in this study. During the 2021 farming season, data for the study was collected from 355 randomly selected farms. Descriptive statistics and a farm budgeting approach were utilized to assess the data. The mean age of respondents was 42.3 years, 85.1% of them were married with an average household of six people. The majority (77.5%) of the respondents were educated with a mean farming experience of 8.6 years. On average, the respondents cultivate 4.2 hectares of land. The budgeting technique showed that a mixture of melon and cowpea has the highest average net farm income, followed by a mixture of melon and Bambara-nut while a mixture of melon and groundnut has the least average net farm income per hectare. The estimated gross margin and net farm income for all the enterprises stood at N 143618.11 and N 135051.13 respectively. The return on the owner's labour and management for all the enterprises is N 87801.13 and the return on investment is 127.58%. This demonstrates that the watermelon crop diversification strategies in the research area are profitable. A melon and cowpea combination was discovered to be more profitable than other firms. Because of this, it is suggested that a large amount of land be set aside for growing this crop.
... Through a crossover trial, Lum et al. investigated the effects of watermelon on thirtythree obese or overweight volunteers who received two cups of watermelon every day over four weeks. Researchers concluded that watermelon intake substantially reduces body mass index, body weight, waist-to-hip ratio, and systolic blood pressure [93]. Also, Massa et al. assessed the effect of watermelon extract on blood pressure. ...
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Watermelon is a nutrient-dense fruit, contrary to the popular assumption that it is primarily composed of water and sugar. Watermelon, the whole fruit, is distinguished by a variety of bioactive molecules with diverse chemical backbones, including phenolics, carotenoids, unsaturated fatty acids, citrulline, as well as numerous vitamins and minerals. Many researchers have considered watermelon as a natural source of biologically active chemicals in previous decades, primarily when evaluating some biomedical features such as antimicrobial, anti-inflammatory, and antioxidant capabilities. This study focuses on the most beneficial bioactive ingredients found in the watermelon and the possibility of utilizing these ingredients to treat a variety of ailments. The results showed that watermelon extracts are considered a valuable source of many beneficial components that can be used for medicinal purposes.
... More than 600 carotenoids have been identified in nature, of which approximately 40 are present in a typical human diet, and approximately 20 have been identified in blood and tissues. ß-Carotene, α-carotene, lycopene, β-cryptoxanthin, and lutein account for more than 90% of the carotenoids in humans [80]. All carotenoids have certain common chemical features, such as a polyisoprenoid structure, the long conjugated chain of double bonds at the center of the molecules, and almost bilateral symmetry around the central double bond [81]. ...
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Cardiovascular diseases (CVDs) are a major global cause of disease and mortality. CVDs are a group of disorders of the heart and blood vessels and include coronary artery disease, cerebrovascular disease, heart failure, and other conditions. The most important behavioral risk factors for heart disease and stroke are diet, physical activity, smoking, and drinking. Increased intake of fruits and vegetables is associated with reducing the risk of metabolic syndrome and CVDs. Red-colored foods align with cardiovascular health by protecting the heart and blood vessels. Red fruits and vegetables include tomatoes, strawberries, raspberries, cranberries, cherries, red apples, beets, and pomegranate. In vitro and in vivo studies, as well as clinical trials, show that the components of red foods demonstrate various potential health benefits against disease. In conclusion, there are many advantages to eating vegetable foods, especially red fruits and vegetables.
... In cup of diced watermelons 461 µg of β-carotene can be found(Story et al. 2010). It helps in exhibition of pro-oxidants and antioxidants(Knight et al. 2010)and have capability to inactive ROS, HDL and LDL(Lum et al. 2019). Many practical results have been estimated about antioxidant activity of β-carotene(Kim et al. 2014). ...
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Food intake and body weight regulation are of special interest for meeting today’s lifestyle essential requirements. Since balanced energy intake and expenditure are crucial for healthy living, high levels of energy intake are associated with obesity. Hence, regulation of energy intake occurs through shortand longterm signals as complex central and peripheral physiological signals control food intake. This work aims to explore and compile the main factors influencing satiating eciency of foods by updating recent knowledge to point out new perspectives on the potential drivers of satiety interfering with food intake regulation. Human internal factors such as genetics, gender, age, nutritional status, gastrointestinal satiety signals, gut enzymes, gastric emptying rate, gut microbiota, individual behavioral response to foods, sleep andcircadian rhythmsarelikely tobeimportantindeterminingsatiety. Besides, theexternal factors (environmentalandbehavioral)impactingsatietyeciency are highlighted. Based on mechanisms related to food consumption and dietary patternsseveralphysical,physiological,andpsychologicalfactorsaect satiety or satiation. A complex network of endocrine and neuroendocrine mechanisms controls the satiety pathways. In response to food intake and other behavioral cues, gut signals enable endocrine systems to target the brain. Intestinal and gastric signals interact with neural pathways in the central nervous system to halt eating or induce satiety. Moreover, complex food composition and structures result in considerable variation in satiety responses for dierent food groups. A better understanding of foods and factors impacting the eciency of satiety could be helpful in making smart food choices and dietary recommendations for a healthy lifestyle based on updated scientific evidence.
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Obesity is associated with the leading causes of death in the worldwide. On the other hand, the intake of vegetables, fruits and fish is related to the reduction of obesity and other metabolic syndromes. This review aims to highlight the role of ingestion of polyphenols and omega-3 polyunsaturated fatty acids (ω-3 PUFAs) in reducing obesity and related metabolic diseases (RMDs). The consumption of vegetables, fish and by-products rich in polyphenols and α-linolenic acid (ALA), as well as oils rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are associated with a decrease in obesity and its RMDs in consumers. Furthermore, we discussed the adequate amount of extracts, powder, polyphenols, ω-3 PUFAs administrated in animal models and human subjects, and the relevant outcomes obtained. Thus, we appeal to the research institutions and departments of the Ministries of Health in each country to develop a food education joint project to help schools, businesses and families with the aim of reducing obesity and other metabolic diseases.
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Purpose of Review Watermelon (Citrullus lanatus) distinctively contains l-citrulline and l-arginine, precursors of nitric oxide (NO), along with polyphenols and carotenoids suggesting a role in cardio-metabolic health. The goal of this paper is to review the preclinical and clinical trial evidence published from 2000 to 2020 to assess watermelon intake and l-citrulline, as a signature compound of watermelon, on cardiovascular and metabolic outcomes, and to identify future directions important for establishing dietary guidance and therapeutic recommendations actionable by health care professionals, patients, and the general public. Recent Findings Watermelon and l-citrulline supplementation reduced blood pressure in human trials. Evidence for benefits in lipids/lipoprotein metabolism is emerging based on human literature and consistently reported in animal models. A role for watermelon intake in body weight control, possibly through satiety mechanisms, warrants further research. Likewise, improved glucose homeostasis in chemically and diet-induced animal models of diabetes is apparent, though limited data are available in humans. Emerging areas include brain and gut health indicated by NO bioavailability in all tissues, and evidence suggesting improvements in gut barrier function and altered microbial composition after watermelon intake that may influence metabolite pools and physiological function. Summary Watermelon fruit contains unique vaso- and metabolically-active compounds. Accumulating evidence supports regular intake for cardio-metabolic health. Future research to determine the amount and frequency of watermelon/citrulline intake for desired outcomes in different populations requires attention to advance preventative and therapeutic strategies for optimal health and disease risk reduction.
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Mangos are an understudied fruit rich in fiber and polyphenols that have been linked to better metabolic outcomes and promotion of satiety. The purpose of this study was to examine the effect of mango consumption on postprandial glucose, insulin, and satiety responses. Using a randomized crossover study design, 23 overweight and obese men and women consumed 100 kcal snacks of fresh mangos or isocaloric low-fat cookies on two separate occasions. Insulin and satiety hormones were measured at baseline and 45 min post-snack consumption. Glucose was measured at baseline, 30, 60, 90, and 120 min after snack consumption. Satiety questionnaires were completed at baseline and every 20 min for 120 min post-consumption. Both mangos and low-fat cookies increased insulin, with a significantly lower increase for mangos compared with low-fat cookies at 45 min post-snack consumption (P ≤ .05). Glucose increased at 30 min for both snacks; however, the increase was significantly higher for low-fat cookie consumption (P ≤ .05). Cholecystokinin increased after mangos and low-fat cookie consumption (P ≤ .05); however, no differences were detected between the snacks. Adiponectin increased after mango consumption (P ≤ .05) but not after low-fat cookies. Mango consumption reduced hunger, anticipated food consumption and thirst, and increased feelings of fullness (P ≤ .05). Low-fat cookie consumption increased fullness for a shorter time period and did not reduce participants' desire to eat. These results suggest that relative to a refined cookie snack, mangos promote greater satiety and improve postprandial glycemic responses. Future research on long-term effects of mango consumption on food intake, weight control, and glucose homeostasis is warranted. Clinical Trial Registration number: #NCT03957928.
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Purpose of review: L-Citrulline, either synthetic or in watermelon, may improve vascular function through increased L-arginine bioavailability and nitric oxide synthesis. This article analyses potential vascular benefits of L-citrulline and watermelon supplementation at rest and during exercise. Recent findings: There is clear evidence that acute L-citrulline ingestion increases plasma L-arginine, the substrate for endothelial nitric oxide synthesis. However, the subsequent acute improvement in nitric oxide production and mediated vasodilation is inconsistent, which likely explains the inability of acute L-citrulline or watermelon to improve exercise tolerance. Recent studies have shown that chronic L-citrulline supplementation increases nitric oxide synthesis, decreases blood pressure, and may increase peripheral blood flow. These changes are paralleled by improvements in skeletal muscle oxygenation and performance during endurance exercise. The antihypertensive effect of L-citrulline/watermelon supplementation is evident in adults with prehypertension or hypertension, but not in normotensives. However, L-citrulline supplementation may attenuate the blood pressure response to exercise in normotensive men. Summary: The beneficial vascular effects of L-citrulline/watermelon supplementation may stem from improvements in the L-arginine/nitric oxide pathway. Reductions in resting blood pressure with L-citrulline/watermelon supplementation may have major implications for individuals with prehypertension and hypertension. L-Citrulline supplementation, but not acute ingestion, have shown to improve exercise performance in young healthy adults.
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Consuming carbohydrate- and antioxidant-rich fruits during exercise as a means of supporting and enhancing both performance and health is of interest to endurance athletes. Watermelon (WM) contains carbohydrate, lycopene, l-citrulline, and l-arginine. WM may support exercise performance, augment antioxidant capacity, and act as a countermeasure to exercise-induced inflammation and innate immune changes. Trained cyclists (n = 20, 48 ± 2 years) participated in a randomized, placebo controlled, crossover study. Subjects completed two 75 km cycling time trials after either 2 weeks ingestion of 980 mL/day WM puree or no treatment. Subjects drank either WM puree containing 0.2 gm/kg carbohydrate or a 6% carbohydrate beverage every 15 min during the time trials. Blood samples were taken pre-study and pre-, post-, 1 h post-exercise. WM ingestion versus no treatment for 2-weeks increased plasma l-citrulline and l-arginine concentrations (p < 0.0125). Exercise performance did not differ between WM puree or carbohydrate beverage trials (p > 0.05), however, the rating of perceived exertion was greater during the WM trial (p > 0.05). WM puree versus carbohydrate beverage resulted in a similar pattern of increase in blood glucose, and greater increases in post-exercise plasma antioxidant capacity, l-citrulline, l-arginine, and total nitrate (all p < 0.05), but without differences in systemic markers of inflammation or innate immune function. Daily WM puree consumption fully supported the energy demands of exercise, and increased post-exercise blood levels of WM nutritional components (l-citrulline and l-arginine), antioxidant capacity, and total nitrate, but without an influence on post-exercise inflammation and changes in innate immune function.
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Previous studies have shown that watermelon extract reduces blood pressure through vasodilation. However, those studies have not verified whether sympathetic nervous activity is influenced by watermelon extract. This study aimed to evaluate the effect of supplementation with watermelon extract for 6 weeks on blood pressure and sympathovagal balance of prehypertensive and hypertensive individuals. Forty volunteers participated in a randomized, double-blind, experimental and placebo-controlled study. They consumed 6 g of watermelon extract daily (n = 20; age 48.7 ± 1.9 years, 10 men) or a placebo (n = 20; age 47.4 ± 1.2 years, 11 men) for 6 weeks. Blood pressure and cardiac autonomic modulation were measured. Watermelon extract promoted a significant reduction in systolic (137.8 ± 3.9 to 126.0 ± 4.0 mmHg, p < 0.0001) and diastolic (79.2 ± 2.2 to 72.3 ± 2.0 mmHg, p < 0.001) blood pressure, but showed no differences compared to the placebo group. This significant reduction in blood pressure occurred without a significant change in sympathovagal balance from the beginning (1.7 ± 0.1) to the end of the study (1.7 ± 0.4). In conclusion, supplementation with watermelon extract reduces systolic and diastolic blood pressure in prehypertensive and hypertensive individuals, but does not alter the cardiac autonomic modulation of these individuals.
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Objective: To test the hypolipidemic effect of watermelon extract (Citrullus lanatus) and the influence of the methylenetetrahydrofolate reductase genotype (MTHFR C677T) on supplementation response. Methods: This is an experimental clinical phase II randomized and double-blind study. Forty-three subjects with dyslipidemia were randomly divided into 2 groups: experimental (n = 22) and control (n = 21) groups. The subjects were supplemented daily for 42 days with 6 g of watermelon extract or a mixture of carbohydrates (sucrose/glucose/fructose). Results: The use of watermelon extract reduced plasma total cholesterol (p < 0.05) and low-density lipoprotein (p < 0.01) without modifying triglycerides, high-density lipoprotein, and very low-density lipoprotein values. Only carriers of the T allele (MTHFR C677T) showed decreasing concentrations of low-density lipoprotein (p < 0.01). No changes in anthropometric parameters analyzed were observed. This is the first study to demonstrate the beneficial effect of the consumption of watermelon extract in reducing plasma levels of lipids in humans. The MTHFR C677T polymorphism did not affect the plasma lipid concentration but made individuals more responsive to treatment with watermelon. Conclusions: The consumption of this functional food represents an alternative therapy in the combined treatment of patients with dyslipidemia, promoting health and minimizing the development of risk factors for cardiovascular diseases.
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Watermelon (Citrullus lanatus) is rich in l-citrulline, an l-arginine precursor that may reduce cardiovascular disease risk. The purpose of this study was to compare the effects of watermelon powder and l-arginine on lipid profiles, antioxidant capacity, and inflammation in rats fed an atherogenic diet. We hypothesized that watermelon and l-arginine would increase antioxidant capacity and reduce blood lipids and inflammation by modulating hepatic gene expression. Male Sprague-Dawley rats aged 21 days (N = 32) were assigned to 3 groups and fed diets containing watermelon powder (0.5% wt/wt), l-arginine (0.3% as 0.36% l-arginine HCl wt/wt), or a control diet for 9 weeks. Watermelon and l-arginine supplementation improved lipid profiles by lowering serum concentrations of triglycerides, total cholesterol, and low-density lipoprotein cholesterol (P < .050). Serum concentrations of C-reactive protein were significantly lower (P < .050) in the watermelon and l-arginine groups. Rats in the watermelon and l-arginine groups showed reduced oxidative stress, increased total antioxidant capacity, and higher concentrations of superoxide dismutase and glutathione S-transferase (P < .050). Concentrations of aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase were lower (P < .050) in the watermelon and l-arginine groups. Watermelon and l-arginine consumption upregulated hepatic gene expression of endothelial nitric oxide synthase and downregulated expression of fatty acid synthase, 3-hydroxy-3-methylglutaryl-CoA reductase, sterol regulatory element-binding protein 1, sterol regulatory element-binding protein 2, cyclooxygenase-2, and nuclear factor-κB p65 (P < .050). The results support the hypothesis that watermelon and arginine improve cardiovascular disease risk factors including lipid profile, antioxidant capacity, and inflammation by altering relevant gene expression.
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The objective of this study was to assess the potential of dried apple to regulate acute blood glucose, insulin, satiety, and total plasma antioxidant levels, and to explore the effect of dried apple on cognitive responses. Twenty-one healthy, normal-weight subjects completed the study which used a randomized crossover design with repeated measures. After a fast of 10 h, a standardized serving size of either dried apple or muffins was consumed. Blood glucose, insulin, and antioxidant concentrations were measured at 0, 15, 30, 45, 60, 90, and 120 min postprandial, and satiety was assessed every 15 min for 2 h. Cognitive tests were administered before and 2 h after consumption of the test food. The dried apple had significantly higher phenolic content and antioxidant activities than the muffin (P ≤ .05). Consumption of the dried apples produced significantly lower glucose concentrations at 30- (P ≤ .01; 95% CI [2.93-16.64]), 45- (P ≤ .02; 95% CI [2.41-17.88]), 60- (P ≤ .02; 95% CI [2.10-14.56]), and 120-min (P ≤ .01; 95% CI [8.16-16.80]) time points, and significantly lower (P ≤ .03; 95% CI [0.60-8.70]) insulin concentrations at a 15-min time point than the muffins but offered little consistent differences in antioxidant status, satiety, and cognitive function. These findings suggested that the intake of dried apples could reduce postprandial blood glucose and potentially increase the effectiveness of insulin responses in healthy individuals but offered little consistent differences in antioxidant status, satiety, and cognitive function.
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Objective: The results of several studies showed that energy density of food affects both satiety and food intake. None of them has checked the influence of energy density variation in solid meals in obese subjects. We examined the effect of meal volume on satiety potency of food and its effect on glucose and insulin profiles in obese subjects. Design: Subjects were served a test meal (milk pudding) equal in energy content and composition (fat, protein, carbohydrate) across two volumes : 250 ml and 500 ml. Subjects: Study group: 22 obese subjects without additional diseases, BMI: 37.9 + 7.1. Measurements: The satiety state was assessed on VAS before and after consumption test meal during 180 minutes of observation. During the study every 30 min the blood was taken to determine glucose and insulin profiles. Results: There were no differences in taste assessment of both test foods on VAS scale. Food consumption results in significant reduction of hunger and increase of satiety feelings independently of food volume. The food volume had no important influence on satiety status of study patients during whole study. Only just after ingestion we observed the significant more satiating efficiency of bigger than smaller volume. We didn't also notice any differences in plasma glucose and insulin levels after ingestion of both food volumes. Conclusion: Food volume has only limited influence on satiety state directly after meal consumption but not glucose and insulin plasma concentrations.
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There is a general perception that almost no one succeeds in long-term maintenance of weight loss. However, research has shown that ≈20% of overweight individuals are successful at long-term weight loss when defined as losing at least 10% of initial body weight and maintaining the loss for at least 1 y. The National Weight Control Registry provides information about the strategies used by successful weight loss maintainers to achieve and maintain long-term weight loss. National Weight Control Registry members have lost an average of 33 kg and maintained the loss for more than 5 y. To maintain their weight loss, members report engaging in high levels of physical activity (≈1 h/d), eating a low-calorie, low-fat diet, eating breakfast regularly, self-monitoring weight, and maintaining a consistent eating pattern across weekdays and weekends. Moreover, weight loss maintenance may get easier over time; after individuals have successfully maintained their weight loss for 2–5 y, the chance of longer-term success greatly increases. Continued adherence to diet and exercise strategies, low levels of depression and disinhibition, and medical triggers for weight loss are also associated with long-term success. National Weight Control Registry members provide evidence that long-term weight loss maintenance is possible and help identify the specific approaches associated with long-term success.
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Aiming at investigating the potential effect of minimal dietary changes in NAFLD patients with non-significant fibrosis, 55 patients with NAFLD were enrolled in a randomized controlled clinical trial. Patients were assigned into two isocaloric dietary treatment groups for 24 weeks: (a) nutritional counseling (Control arm, N = 27), (b) nutritional counseling with currants included (two fruit servings, 36 g per day), substituting snacks of similar caloric content (Currant arm, N = 28). Clinical tests, anthropometrics, inflammatory and oxidative stress markers were conducted pre- and post-intervention. A total of 50 patients completed the trial. Significant differences between the two arms post-intervention were observed in fasting glucose and in IL-6 levels, these being significantly decreased only in Currant patients. Body weight, BMI, HbA1c, CRP and EUS values decreased in both arms, differences being insignificant between the two arms post-intervention. Participants in the Currant arm had significantly reduced total body fat, WC and trunk fat. Ultrasound scanning improved significantly in patients snacking currants daily. Also, volunteers enrolled in the Currant arm showed a reduced intake of saturated fatty acids. Because BW regulation has been officially recognised as a treatment approach in NAFLD an additional analysis was repeated in patients adhering to this. Post-intervention, the decrease in IL-6 and in fasting glucose was significantly higher in Currant patients who lost BW compared to their counterparts in the Control arm. Conclusively, minimal modifications in snacking choices, such as the inclusion of dried grapes in diet, are beneficial in NAFLD patients with non-significant fibrosis.
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Background: Previous research indicated that increasing the volume of food by adding water can lead to reductions in energy intake. However, the addition of water affects not only the volume but also the energy density (kJ/g) of foods. No studies have examined the effect of volume independent of energy density on intake. Objective: We examined the effect of food volume independent of energy density on satiety. Design: In a within-subjects design, 28 lean men consumed breakfast, lunch, and dinner in the laboratory 1 d/wk for 4 wk. On 3 d, participants received a preload 30 min before lunch and on 1 d no preload was served. Preloads consisted of isoenergetic (2088 kJ), yogurt-based milk shakes that varied in volume (300, 450, and 600 mL) as a result of the incorporation of different amounts of air. Preloads contained identical ingredients and weighed the same. Results: The volume of the milk shake significantly affected energy intake at lunch (P < 0.04) such that intake was 12% lower after the 600-mL preload (2966 ± 247 kJ) than after the 300-mL preload (3368 ± 197 kJ). Subjects also reported greater reductions in hunger and greater increases in fullness after consumption of both the 450- and 600-mL preloads than after the 300-mL preload. Conclusions: Changing the volume of a preload by incorporating air affected energy intake. Thus, the volume of a preload independent of its energy density can influence satiety.