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Impact of medium and long chain triglycerides consumption on appetite and food intake in overweight men

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Background Medium chain triglycerides (MCT) enhance thermogenesis and may reduce food intake relative to long chain triglycerides (LCT). The goal of this study was to establish the effects of MCT on appetite and food intake and determine whether differences were due to differences in hormone concentrations. Methods Two randomized, crossover studies were conducted in which overweight men consumed 20 g of MCT or corn oil (LCT) at breakfast. Blood samples were obtained over 3 h. In Study 1 (n=10), an ad lib lunch was served after 3 h. In Study 2 (n=7), a pre-load containing 10 g of test oil was given at 3 h and lunch was served 1 h later. Linear mixed model analyses were performed to determine the effects of MCT and LCT oil on change in hormones and metabolites from fasting, adjusting for body weight. Correlations were computed between differences in hormones just before the test meals and differences in intakes after the two oils for Study 1 only. Results Food intake at the lunch test meal after the MCT pre-load (Study 2) was (mean ± SEM) 532 ± 389 kcal vs. 804 ± 486 kcal after LCT (P < 0.05). MCT consumption resulted in a lower rise in triglycerides (P = 0.014) and glucose (P = 0.066) and a higher rise in peptide YY (P = 0.017) and leptin (P = 0.036) compared to LCT (combined data). Correlations between differences in hormone levels (GLP-1, PYY) and differences in food intake were in the opposite direction to expectations. Conclusions MCT consumption reduced food intake acutely but this does not seem to be mediated by changes in GLP-1, PYY, and insulin.
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ORIGINAL ARTICLE
Impact of medium and long chain triglycerides consumption
on appetite and food intake in overweight men
M-P St-Onge
1,2
, B Mayrsohn
1
,MOKeeffe
1,2
, HR Kissileff
1,2
, AR Choudhury
3
and B Laferrère
2
BACKGROUND: Medium chain triglycerides (MCT) enhance thermogenesis and may reduce food intake relative to long chain
triglycerides (LCT). The goal of this study was to establish the effects of MCT on appetite and food intake and determine whether
differences were due to differences in hormone concentrations.
METHODS: Two randomized, crossover studies were conducted in which overweight men consumed 20 g of MCT or corn oil (LCT)
at breakfast. Blood samples were obtained over 3 h. In Study 1 (n= 10), an ad lib lunch was served after 3 h. In Study 2 (n= 7),
a preload containing 10 g of test oil was given at 3 h and lunch was served 1 h later. Linear mixed model analyses were performed
to determine the effects of MCT and LCT oil on change in hormones and metabolites from fasting, adjusting for body weight.
Correlations were computed between differences in hormones just before the test meals and differences in intakes after the two
oils for Study 1 only.
RESULTS: Food intake at the lunch test meal after the MCT preload (Study 2) was (mean ± s.e.m.) 532 ± 389 kcal vs 804 ± 486 kcal
after LCT (Po0.05). MCT consumption resulted in a lower rise in triglycerides (P= 0.014) and glucose (P= 0.066) and a higher rise in
peptide YY (PYY, P= 0.017) and leptin (P= 0.036) compared with LCT (combined data). Correlations between differences in hormone
levels (glucagon-like peptide (GLP-1), PYY) and differences in food intake were in the opposite direction to expectations.
CONCLUSIONS: MCT consumption reduced food intake acutely but this does not seem to be mediated by changes in GLP-1,
PYY and insulin.
European Journal of Clinical Nutrition advance online publication, 30 July 2014; doi:10.1038/ejcn.2014.145
INTRODUCTION
Functional foods, 'those foods that encompass potentially
healthful products including any modied food or ingredient that
may provide a health benet beyond the traditional nutrients it
contains',
1
have been suggested to provide benets for weight
management
2
via decreased lipid storage and uptake, enhanced
rates of fat oxidation and increased satiety.
35
One functional food
that has been proposed to act on both energy expenditure and
energy intake is medium chain triglycerides (MCT). MCT bypass
chylomicron incorporation for lymphatic transportation, providing
the liver with a ready supply of energy and reducing peripheral fat
deposition into adipose tissue.
6,7
In humans, MCT consumption
enhances reductions in adiposity.
8,9
Ex vivo studies have shown that the rate of medium chain fatty
acid oxidation is 10-fold faster than that of long chain fatty acids.
10
Indeed, MCT consumption produces a greater thermic effect when
compared with long chain triglyceride (LCT)
1116
and promotes
satiety in animal models
17,18
and humans.
19,20
Considering these
effects of MCT consumption, it has been hypothesized that
substituting MCT oil for LCT oils could potentially be used as an
adjunct in weight-loss programs.
21
Although an abundance of research on MCTs effects on energy
expenditure and body composition is available,
16,21
their role in
modulating food intake has not been extensively studied
8,20,22
beyond their effect on cholecystokin (CCK). Studies have shown
that long chain fatty acids, but not medium chain fatty acids,
stimulate CCK release to reduce food intake.
23
However, a study by
Drewe et al.
24
does not support the role of endogenous CCK as
being responsible for the food intake reduction after LCT infusion.
One study showed that both MCT and LCT stimulated the release of
peptide YY (PYY), when infused intraduodenally, but that LCT did so
to a greater extent.
25
The authors suggested that the greater effect
of LCT may be because of its stimulation of CCK release, which then
stimulates PYY release. Of note is that those studies have used fat
duodenal infusions rather than oral intakes. In this study, we chose
to provide oils as would be consumed in a typical diet.
The main purpose of this study was to determine whether
(i) MCT consumption suppresses food intake relative to LCT; (ii)
MCT induces a prole of gut hormone responses indicating
increased satiety/reduced appetite signaling relative to LCT and
(iii) the hormonal response to MCT is related to the differences in
food intake after the consumption of MCT or LCT. We
hypothesized (i) lower food intake after a preload high in MCT
compared with LCT; (ii) lower circulating levels of ghrelin and higher
circulating levels of PYY and glucagon-like peptide 1 (GLP-1) after
MCT consumption relative to LCT and (iii) that the effect of MCT on
hormones would be related to the difference in food intake
observed after the consumption of either MCT or LCT. Gibbons
et al.
26
have reported that post-meal levels of ghrelin and GLP-1
were correlated with food intake at an ad libitum meal 3 h later.
PARTICIPANTS AND METHODS
Study participants
Adult men, age 1950 years, with a body mass index of 2529.9 kg/m
2
were
recruited to participate in two separate studies (Study 1, n= 10; Study 2, n=7)
1
College of Physicians and Surgeons, Columbia University, New York, NY, USA;
2
New York Obesity Nutrition Research Center, St. Lukes/Roosevelt Hospital, New York, NY, USA and
3
Department of Biostatistics, Mailman School of Public Health, Columbia University, New York, NY, USA. Correspondence: Dr M-P St-Onge, 622 West 168th Street, PH9-105Q,
New York, NY 10032, USA.
E-mail ms2554@columbia.edu
Received 3 December 2013; revised 22 May 2014; accepted 27 May 2014
European Journal of Clinical Nutrition (2014), 17
© 2014 Macmillan Publishers Limited All rights reserved 0954-3007/14
www.nature.com/ejcn
during the summers of 2009 and 2010. Men were recruited from the
Columbia University/St. Lukes-Roosevelt Hospital area (New York, NY, USA)
via yers and online advertisements. Smokers and those with recent
weight change (410 lbs in the previous 3 months), excessive caffeine use
(46 caffeinated beverages per day), severe chronic health conditions,
allergies to any of the food products or ingredients provided in this study
or taking medications known to affect energy expenditure or gastro-
intestinal function were excluded from the study. These studies were
approved by the St Lukes-Roosevelt Hospital Institutional Review Board
and all participants provided informed consent prior to the start of
the study.
Protocol details
Both studies employed a 2-arm, randomized, single-blind, cross-over
design with each arm consisting of one test day differing in the type of oil
incorporated in the breakfast: MCT oil (Neobee 1053, Stepan Company,
Northeld, IL, USA) or corn oil (LCT, Mazola, ACH Food Companies,
Cordova, TN, USA). A random digit table was used to determine test oil
sequence. The random allocation sequence and participant enrollment
were determined by a study investigator. Test days were held at least
3 days, but no more than 14 days, apart.
For 2 days prior to test day, participants were asked to refrain from
alcohol consumption. In addition, they were asked not to participate in any
structured exercise the day before each test day and to record their food
intake at dinner and consume the same meal on the night prior to their
second test day. They were also instructed to drink approximately 1.9l of
water the day before each test day to ensure proper hydration. These
precautions were implemented to ensure a greater degree of consistency
between test periods. Participants were asked to fast overnight for 12 h
prior to testing.
Each test day was performed at the St Lukes/Roosevelt Hospital
Outpatient Clinical Research Resource of the Irving Center for Translational
Research (Columbia University, New York, NY, USA) in the morning. Upon
arrival, anthropometric measurements were taken and a catheter was
inserted in an antecubital vein for frequent blood sampling. Participants
then consumed the breakfast meal containing 20 g of oil over a 10-min
period. Immediately before and at xed time points after breakfast, blood
samples were drawn from the catheter for hormone and metabolite
measurements. At the end of the 3- h blood sampling protocol,
participants from Study 1 were served an ad libitum single item lunch
test meal. Participants from Study 2 were given a preload containing 10 g
of the test oil, followed 1 h later by the ad libitum single item lunch. For the
ad libitum lunch test meal, men were instructed to eat as much as they
wanted until they were satised. Total food intake was measured by
weighing the food portion before and after lunch.
Test breakfast meals and preload
Breakfast meals differed in nutrient composition between Study 1 and
Study 2 (Table 1) but contained the same amount of test oil and were
consumed within 10 min in both studies. Participants in Study 1 received a
mufn (20 g of test oil) and 5 oz (148 ml) of orange juice. Mufns were
made from 71.5 g of fat-free mufn mix, either raisin bran or spice apple
bran (Bobs Red Mill, Milwaukie, OR, USA). Participants in Study 2 received a
liquid meal replacement (14 oz of Boost, Nestle Healthcare Nutrition,
Fremont, MI, USA) to which 20 g of test oil was added. This dose of oil was
used because we have previously showed that consumption of 1824 g/day
of MCT oil enhances weight loss relative to LCT
27
and Dulloo et al.
11
have
shown that 1530 g/day of MCT raise 24-h energy expenditure relative to
LCT. The oils did not differ in taste. In Study 1, participants were not given
instructions on how to consume the breakfast and the order of intake of
the juice and mufn may have differed between participants and between
test days. This may have affected transit time and hormone release. The
breakfast meal for Study 2 was switched to a liquid meal to ensure greater
consistency in gastric emptying time and a more uniform consumption
and nutrient absorption pattern.
Participants in Study 2 were given a preload of yogurt (Dannon Light &
Fit yogurt, Dannon, Allentown, PA, USA; Table 1) containing 10 g of the test
oil 3 h after breakfast consumption. Provision of a preload is commonly
done to assess the satiating properties of a food. We chose to
provide 711.6 kJ as this is consistent with a snack, which typically provides
795.31172.1 kJ.
28
Blood sampling protocol
For both Study 1 and 2, blood samples were obtained in the fasted state
immediately before (15 min) and after test breakfast consumption (0 min)
and at 30, 45, 60, 120, and 180 min. Study 2 participants provided
additional samples at 15, 75, 90 and 150 min. This 3-h sampling period has
been used by others to assess the impact of meal nutrient composition on
appetite-related hormones.
2931
Samples were collected in EDTA-coated
chilled tubes for the measurement of gut hormones. Tubes were
pretreated with aprotinin (0.6 TIU per ml of blood) and dipeptidyl
peptidase 4 inhibitor (10 μl per ml of blood, for GLP-1 and total PYY
assays only) to prevent the degradation of gut hormones. Upon collection,
blood was immediately placed on ice. Plasma was separated within
60180 min of collection via centrifugation for 20 min at 4 °C. Samples to
be analyzed for active ghrelin were acidied with 50 μl of 1N HCl and then
frozen at 80 °C until assayed.
All hormone analyses were performed in duplicate in the Hormone and
Metabolite Core Laboratory of the New York Obesity Nutrition Research
Center. Glucose measurements were performed with a glucose analyzer
(Analox Instruments USA Inc, Lunenburg, MA, USA). Insulin and total and
active ghrelin were assayed using RIA (EMD Millipore, Billerica, MA, USA).
Serum leptin was measured in duplicate aliquots using a double-antibody
RIA (Linco Research Products Inc., St Charles, MO, USA). Total PYY was
determined according to Millipore procedure using an antibody that
recognizes both 136 and 336 forms of human PYY. Total GLP-1 was
measured by RIA (Phoenix Pharmaceutical, Belmont, CA, USA) after plasma
extraction with 95% ethanol. This assay is 100% specic for GLP-1
7-36
,
GLP-1
9-36
and GLP-1
7-37
and does not cross-react with glucagon (0.2%),
GLP-2 (o0.001%) or exendin (o0.0.1%). Triglyceride (TG) levels were
assessed using an Ektachem DT II System (Johnson and Johnson Clinical
Diagnostics, Rochester, NY, USA) with appropriate standards and reagents
for Study 2 participants only. All other hormones and metabolites were
assessed in both studies.
Food intake measurement
At the end of the 3- h testing period, participants in Study 1 were served a
one item ad libitum lunch test meal (Stouffers macaroni and beef, Nestle
USA, Wilkes-Barre, PA, USA). In Study 2, a preload was served at 3h and the
single item ad libitum lunch (Penne Arrabiata, Trader Joes, Monrovia, CA,
USA) was provided 1 h later. One hour was noted as the time where the
difference in hunger ratings was seemingly greatest between MCT and LCT
and has been used by others previously.
32
In both studies, participants
were served in excess of their predicted energy intakes and instructed by
the investigator to eat as much as you would like of this meal until you are
Table 1. Characteristics of study meals
Meal characteristics Study 1 Study 2
Breakfast meal Mufn with
orange juice
Boost shake
with test oil
Total energy (kJ) 2671 2510
Carbohydrate (g) 105 71.6
Protein (g) 9.6 17.5
Fat (g) 20 27
Test oil (g) 20 20
Preload n/a Yogurt with 10 g
test oil added
Total energy (kJ) 728
Carbohydrate (g) 16
Protein (g) 5
Fat (g) 10
Test oil (g) 10
Lunch meal Stouffers macaroni
and beef
Trader Joes Penne
Arrabiatta
Total energy (kJ) 5146 4971
Carbohydrate (g) 135 174
Protein (g) 66 42
Fat (g) 48 36
Abbreviation: n/a, not applicable.
Regulation of appetite by medium chain fatty acids
M-P St-Onge et al
2
European Journal of Clinical Nutrition (2014) 1 7 © 2014 Macmillan Publishers Limited
satised. Total food intake at the ad libitum lunch test meal was recorded
by weighing the food pre- and post-meal. Water was available to drink
with the meal but its intake was not recorded.
Anthropometric measurements
Body weight was measured on a standard balance beam scale to the
nearest 0.5 kg with the participant wearing light clothing and without
shoes on each test day, in the fasted state. Height was measured using a
wall-mounted stadiometer to the nearest 0.5 cm with the participants
shoeless. Waist circumference was measured halfway between the lowest
rib and the iliac crest using a non-stretchable measuring tape.
33
The
average of two measurements was used in the analyses. These
measurements were taken in the fasted state when the participant arrived
at the laboratory.
Statistical analyses
Appetite and hormone data were analyzed using a linear mixed model
analysis using R software (http://cran.r-project.org) and SAS (version 9.2,
SAS Institute, Cary, NC, USA). Each response measure was tested using a
likelihood ratio test to determine if log-transformation would signicantly
improve the normal approximation of the measure. It was established
that the normal approximation would not improve because of
log-transformation for any of the measures. Normality of our test statistics
(t-test and F-test used in linear mixed model analyses) was ensured as 14
measures each taken from 17 (7 in some cases) participants gave us at
least 98, and at most 238, data points. Although we have performed
multiple tests in this study, an adjustment for multiple comparisons was
not required because it is only necessary when multiple tests are used for
testing a single hypothesis. In this study, each hypothesis was examined
using a single test.
Test oil (LCT vs MCT) was used as a xed effect and time as a linear
variable in hormone data. However, when fasting values were used as
response measures, time was not used as an independent variable. Body
weight was used as a covariate and subject was treated as a random effect.
A test oil × time interaction was included in the models initially but was
removed if it was not signicant. Data are reported with test oil and time as
xed effects, subject as a random effect, and body weight as a covariate.
Statistical analyses were performed for both studies combined (n= 17)
and also for Study 2 (n= 7) separately because the composition of the
breakfast meals was too different between studies: liquid and solid in
Study 1 vs liquid only in Study 2. Hormone data from Study 2 are
presented in the gures. Food intake data are reported separately for each
study as the difference in protocol for this measurement precludes
combining data. In Study 1, there was a 3-h time gap between breakfast
and the lunch test meal, whereas in Study 2, a preload was served at 3 h
and the lunch test meal was administered 1 h later. Data are presented as
means ± s.e.m. Signicance was considered as Po0.05.
Pearson correlations were performed to assess the relationship between
hormone concentration at 180 min after breakfast and food intake at the
ad libitum lunch test meal as well as change in hormone/metabolite
concentration at 180 min from fasting and food intake at the ad libitum
lunch in Study 1. Pearson correlations were also performed to assess the
relationship between the difference in hormone concentrations at 180 min
between MCT and LCT and the difference in food intake at the ad libitum
lunch in Study 1. Study 2 participants were not included in these analyses
because they received a preload after the 180 min blood draw. Correlations
were performed with both test oils combined and separately by test oil.
RESULTS
Twenty men were recruited (Study 1, n= 13; Study 2, n= 7) and 17
completed (Study 1, n= 10; Study 2, n= 7, Table 2) the study. Two
participants dropped out after screening because of scheduling
conicts, another dropped out in the middle of the rst test day
after feeling faint and nauseated following consumption of the
MCT-containing breakfast. Another participant (Study 2) reported
diarrhea following the MCT test day, but remained in the study. No
other side effects were noted.
Food intake
Food intake at the ad libitum test lunch did not differ by oil type in
Study 1 (MCT, 2548.0 ± 459.6 kJ vs LCT, 2773.2 ± 531.6 kJ, P= 0.41).
In Study 2, when participants received a 711.6-kJ preload 1 h
before lunch, food intake at lunch was signicantly lower during
the MCT test day (MCT, 2227.0 ± 616.2 kJ vs LCT, 3369.3 ± 769.0 kJ,
Po0.050).
Hormones and metabolites: Absolute change
In the combined analyses, there was a signicant effect of time on
change in glucose concentrations (P= 0.025) and a trend for an
effect of oil with a lower rise in glucose with MCT consumption
compared with LCT (P= 0.066) that was signicant in Study 2
alone (P= 0.0017; Figure 1a). Concurrent with these results, the
change in insulin was not affected by oil in the combined analyses
(P= 0.99) but there was a trend for a lower rise in insulin (effect of
oil P= 0.13; time P= 0.017) when data from Study 2 were analyzed
separately (Figure 1b). There was a signicant time × oil
interaction on TG concentrations (P= 0.0046) with a lower rise in
TG (Figure 1c) with MCT consumption compared with LCT
(Study 2).
In the combined analyses, leptin levels after the MCT-containing
breakfast increased to a greater extent compared with LCT
consumption (effect of oil P= 0.036; time P= 0.62). Active ghrelin
concentration after the MCT-containing breakfast was reduced to
a lesser extent compared with LCT (effect of oil P= 0.0031; time
P= 0.10), but the effect of oil type on the change in total ghrelin,
albeit in the same direction, was not signicant (effect of oil
P= 0.21; time P= 0.20). When the analyses were restricted to Study 2,
the effect of oil type on changes in leptin was stronger (effect of
oil Po0.001; time P= 0.038; Figure 2a), that is, leptin remained
higher after MCT consumption relative to LCT, whereas the
change in active ghrelin was no longer signicant (effect of oil
P= 0.28; time P= 0.95).
There was a signicant effect of oil (P= 0.017) and time
(Po0.0001) on total PYY with a greater rise in total PYY post-
prandially with MCT oil than LCT (Study 2 alone: effect of oil
P= 0.030; time Po0.0001; Figure 2b). GLP-1 was not affected by
oil type in the combined analysis (P= 0.39) or in Study 2 alone
(P= 0.40; Figure 2c), although there was a signicant effect of time
in the combined analysis (P= 0.0097) but not in Study 2 alone
(P= 0.071).
Online Supplementary material provides information on
percent change in hormone concentrations from baseline.
Correlation between hormones and food intake at the ad libitum
lunch
Food intake at the ad libitum lunch was negatively correlated with
leptin concentrations at time 180 min when both test oils were
combined (r=0.46, P= 0.037). However, food intake at the ad
libitum lunch test meal was positively correlated with GLP-1
(r= 0.81, Po0.0001), PYY (r= 0.52, P= 0.018), and percent change
Table 2. Characteristics of study participants
Characteristics All participants Study 1 Study 2
Age (year) 39.4 ±1.8 39.2 ±2.7 39.6 ±2.1
Body weight (kg) 88.9 ±2.3 87.1 ±1.7 91.9 ±5.1
Body mass index (kg/m
2
)28.2±0.3 28.1±0.6 28.4±0.5
Height (m) 1.77 ±0.02 1.76 ±0.01 1.79 ±0.04
Systolic blood pressure (mm Hg) 122 ±2 117 ±2 127 ±3
Diastolic blood pressure (mm Hg) 80 ±179±282±2
Ethnicity (C, AA, H, O) 5, 8, 2, 2 3, 7, 0, 0 2, 1, 2, 2
Abbreviations: AA, African Americans; C, Caucasian; O, Other. Results are
means ±s.e.m., n=17 for all participants, 10 for Study 1, and 7 for Study 2.
Regulation of appetite by medium chain fatty acids
M-P St-Onge et al
3
© 2014 Macmillan Publishers Limited European Journal of Clinical Nutrition (2014) 1 7
in PYY from fasting (r= 0.56, P= 0.010). There was a trend for food
intake to be correlated with percent change in insulin concentra-
tions (r= 0.44, P= 0.053). Those correlations indicate that those
with lower leptin and higher GLP-1, PYY and change in PYY and
insulin from fasting had greater intakes at the ad libitum meal.
When correlations were run separately by oil type, only GLP-1
concentrations were correlated with food intake after the MCT-
rich breakfast (r= 0.89, P= 0.0005), indicating that higher GLP-1
concentrations pre-meal were associated with greater food intake.
Intake at the ad libitum lunch following the LCT breakfast was
correlated with GLP-1 (r= 0.74, P= 0.037), percent change in
insulin (r= 0.66, P= 0.038) and percent change in PYY (r= 0.78,
P= 0.0073). Percent change in leptin tended to be inversely
correlated with food intake (r=0.62, P= 0.058): a rise in leptin
was associated with lower intakes at the ad libitum lunch
test meal.
The difference in food intake between MCT and LCT was
negatively correlated with the difference in total ghrelin between
MCT and LCT immediately before lunch (r=0.85, P= 0.0017).
There was also a trend for a positive correlation between the
difference in food intake and the difference in insulin concentra-
tions with MCT and LCT breakfast meals (r= 0.60, P= 0.069). Also,
the difference in food intake between MCT and LCT tended to be
correlated with the difference in the area under the curve for
glucose (r= 0.581, P= 0.078) and insulin (r= 0.59, P= 0.073). There
was no signicant correlation for the difference in leptin, GLP-1,
PYY or ghrelin area under the curve.
DISCUSSION
This report provides results of studies examining the effects of
MCT vs LCT consumption on food intake and a wide range of
hormones involved in food intake control, and metabolic risk
factors. No previous study has examined the effects of MCT
consumption on leptin, ghrelin, PYY and GLP-1, specically. We
show that food intake is lower after an MCT-rich preload
compared with an LCT-rich preload and that leptin and PYY
levels remained higher after MCT consumption compared with
LCT. These results suggest that MCT consumption may trigger the
release of satiety signals more effectively than LCT. However,
correlations between hormone levels and food intake were not in
the direction expected. Moreover, GLP-1 concentrations were not
affected by the type of oil consumed at breakfast and active
ghrelin was reduced to a lesser extent, in the combined analysis,
with MCT consumption. In line with these data, MCT is known to
be a good substrate for the conversion of ghrelin to active ghrelin,
without necessarily affecting total ghrelin concentrations.
34
However, why MCT, which trigger ghrelin acylation via ghrelin
O-acyltransferase, a seemingly orexigenic process,
35
would also be
associated with weight loss and increased reduction in adiposity
27
warrants further investigation. We also found that MCT consump-
tion leads to lower post-prandial glucose and TG than LCT
consumption.
That differences in appetite-regulating hormones were not
related to differences in food intake is puzzling. In fact, the
correlation between differences in ghrelin levels and differences in
food intake between MCT and LCT was in the opposite direction
than expected, as were correlations of food intake with GLP-1 and
PYY. Gibbons et al.
26
have assessed the effects of various
macronutrients on ghrelin, GLP-1 and PYY levels and reported
signicant associations between changes in circulating levels of
GLP-1 and ghrelin and food intake at an ad libitum meal, despite
no difference in food intake between test diets. On the basis of
this, we would have expected the greater rise in PYY after MCT
consumption relative to LCT to be related to lower food intake at
the ad libitum meal. On the other hand, van der Klaauw et al.
36
also found signicant differences in PYY and GLP-1 in response to
meals varying in protein content with no differences in food
intake at a test meal. Other studies examining the role of protein
on appetite-regulation have assessed hormone concentrations.
Leidy et al.
37
found lower ghrelin and higher leptin after
consumption of a high protein breakfast compared with skipping
breakfast but there was no difference when compared with the
-10
0
10
20
30
40
50
-15 0 15 30 45 60 75 90 120 150 180
Glucose, absolute change from baseline
(mg/dL)
Time relative to breakfast consumption (min)
0
20
40
60
80
100
120
-15 0 15 30 45 60 75 90 120 150 180
Insulin, absolute change from basleine
(µU/mL)
Time relative to breakfast consumption (min)
-10
0
10
20
30
40
50
60
70
80
90
-15 0 15 30 45 60 75 90 120 150 180
Triglycerides, absolute change from
baseline (mg/dL)
Time relative to breakfast consumption (min)
Figure 1. Absolute change from baseline in glucose (a), insulin (b)
and triglycerides (c) in response to a meal containing MCT oil (black
squares) and LCT oil (open squares) in Study 2. Blood samples were
obtained after consumption of a liquid meal containing 20 g of
either MCT oil or corn oil (LCT). Data were analyzed using linear
mixed model, controlling for body weight. The meal was provided
immediately before the time 0 blood draw. There was a signicant
effect of oil type on glucose (P=0.0017) and a trend for insulin
(P=0.13). There was a signicant effect of time on insulin (P=0.017)
and a time × oil interaction on triglycerides (P=0.0046). Data
represent means ±s.e.m., n=7.
Regulation of appetite by medium chain fatty acids
M-P St-Onge et al
4
European Journal of Clinical Nutrition (2014) 1 7 © 2014 Macmillan Publishers Limited
normal protein breakfast; food intake was not assessed in that
study. Ratliff et al.
31
also found that an egg breakfast led to lower
glucose, insulin and ghrelin area under the curve over 3h post
consumption relative to a breakfast consisting of bagel and cream
cheese but found no effect of breakfast type on leptin, GLP-1 and
PYY. It is important to note, however, that our study was not
meant to establish a mechanism of action by which MCT
modulation of appetite-regulating hormones could affect satiety
and food intake. Prior to conducting this study, the effects of MCT
consumption on circulating levels of ghrelin, PYY and GLP-1 were
relatively unknown and this study provides some basic informa-
tion on the effects of MCTon those hormones. Future studies are
needed to determine whether changes in these hormones
mediate the effects of MCT consumption on food intake.
From the results obtained in this study, we posit that changes in
gut hormones might not be the primary modulators of food intake
control following MCT consumption. Thermal and oxidative
pathways may be a more likely mechanism. In fact, prior research
by our group and others has shown that MCT can enhance
thermogenesis relative to LCT
1113,16,21,38
and increases in thermic
effect of food have been correlated with enhanced satiety.
39
Although the association between substrate oxidation rate and
energy intake has not been consistently observed,
40
others have
proposed that fatty acid oxidation rate could inuence appetite
and subsequent food intake.
39,41
It is therefore plausible that the
thermogenic- and fat oxidation-enhancing effects of MCT could
be involved in appetite regulation, leading to lower energy
intakes. This remains to be addressed directly.
The effects of MCT on food intake may be acute, rather than
long-acting. In the present study, there was no effect of MCT vs
LCT at breakfast on food intake 3 h later (Study 1), whereas food
intake 1 h after a preload (Study 2) was reduced. It is unfortunate
that no blood samples were obtained after the preload and prior
to the ad libitum lunch test meal in Study 2 to assess correlations
between hormones and food intake. Follow-up studies would be
needed to perform this measurement and also to test the effects
of hormone antagonists on food intake after MCT- and LCT-rich
breakfasts. This would truly help uncover a mechanism linking
hormonal responses to MCT consumption and food intake. For
example, PYY, a hormone previously demonstrated to induce
satiation when infused, and described as being secreted in
proportion to macronutrient intake,
42
was higher after MCT than
LCT consumption. Further studies with blockers of PYY receptors
in conjunction with MCT consumption would be needed to test
whether an increase in PYY could be one mechanism by which
MCT induces satiation.
Data from Study 2 demonstrate a lower rise in TG with MCT
consumption relative to LCT after the test breakfast. This
corroborates data from Maki et al.
43
who found a lower TG
incremental area under the curve over 8 h after consumption of a
milkshake containing 30 g of MCT compared with LCT (mix of high
oleic safower oil, canola oil, soy oil and safower oil). However,
contrary to our results, that study reported higher median blood
glucose levels at 2 h after MCT compared with LCT consumption.
43
The difference in blood sampling protocol between our two
studies may explain the different results: Maki et al.
43
sampled
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
-15 0 15 30 45 60 75 90 120 150 180
Leptin, absolute changr from baseline
(ng/dL)
Time relative to breakfast consumption (min)
0
2
4
6
8
10
12
14
16
18
20
-15 0 15 30 45 60 75 90 120 150 180
GLP-1, absolute change from baseline
(pg/mL)
Time relative to breakfast consumption (min)
0
10
20
30
40
50
60
70
80
Total PYY, ansolute change from
baseline pg/mL
20
25
30
35
40
45
50
Active ghrelin, absolute change from
baseline (pg/mL)
Time (relative to breakfast consumption (min)
Time relative to breakfast consumption (min)
-15 0 15 30 45 60 75 90 120 150 180
-15 0 15 30 45 60 75 90 120 150 180
Figure 2. Absolute change from baseline for leptin (a), GLP-1 (b), total PYY (c) and active ghrelin (d) in response to a meal containing MCT oil
(black squares) and LCT oil (open squares) in Study 2. Data were analyzed using linear mixed model, controlling for body weight. The meal was
provided immediately before the time 0 blood draw. There was a signicant effect of oil type and time on leptin (Po0.001 and 0.038,
respectively), PYY (P=0.030 and o0.0001, respectively) and active ghrelin (P=0.0031; trend for time P=0.10, respectively). There was no
effect of oil type on GLP-1 (P=0.40) but a trend for an effect of time (P=0.071). Data represent means ±s.e.m., n=7.
Regulation of appetite by medium chain fatty acids
M-P St-Onge et al
5
© 2014 Macmillan Publishers Limited European Journal of Clinical Nutrition (2014) 1 7
blood every 2 h for 8 h following the breakfast meal, whereas we
had frequent samples starting immediately after the meal. By not
sampling blood before 2 h post-prandially, the glucose peak may
have been missed. This is evident from our 120 min data point,
which would have prompted different conclusions in the present
study as well. In addition, Broussolle et al.
44
noted more
pronounced reductions in plasma glucose with a 1:1 intravenous
infusion of coconut oil, a rich source of MCT, to soy oil compared
with saline or soy oil infusion alone in healthy normal weight men.
Future studies should examine the long-term effects of MCT
consumption on glucose and lipid proles.
To date, only two studies have examined the effects of MCT on
satiety-modulating hormones such as CCK.
40,46
It has been well
established that the regulation of CCK release following con-
sumption of fat is chain length-dependent, with long chain fatty
acids exerting a greater effect than short and medium chain fatty
acids.
41,46
An analysis of CCK was not included in the present
study and this could be considered a weakness. However, on the
basis of prior knowledge of the regulation of CCK release, LCT
would have elicited a larger release of CCK than MCT. Measure-
ment of apolipoprotein A-IV, which is secreted in response to
dietary fats,
49
may have also been relevant.
Other weaknesses of the present study include its small sample
size, the difference in the format of the breakfast meals and lack of
provision of a preload before the ad libitum lunch test meal in
Study 1. Also, although we have exhaustive objective information
on food intake and its hormonal controls, we did not take
subjective measures of appetite and satiety, which would have
provided additional information. Our study may have been under-
powered to detect some differences between test oils but this was
a pilot study and the data provided can be used as the basis for a
larger study in the future. On the basis of the exploratory nature of
this study, a small sample size was warranted to avoid wasting
resources and unduly performing research on healthy participants.
None of the hypothesis tests should be taken as denitive but
rather as indicative of potential effects, subject to conrmation.
Our study has several strengths. We used a crossover design
and enrolled only overweight men, reducing the variability of our
results. On the other hand, this prevents extrapolation to women
or normal weight individuals. Our study included puried MCT oil
and provided identical breakfast test meals within each study.
Additionally, we obtained frequent blood samples over a 3-h post-
prandial period and analyzed a variety of hormones and
metabolites that could be involved in the appetite-regulating
effect of foods.
The results from the present study suggest that fats differing in
fatty acid chain length and saturation level differentially affect the
secretion of metabolites and hormones that regulate food intake.
However, those differences were not correlated with differences in
food intake. These results prompt further research in the
mechanism by which MCT consumption could modulate food
intake to lead to improved weight management. This report
further provides evidence that acute intakes of up to 20 g of MCT
do not adversely affect glucose and TG concentrations. The long-
term safety, and potentially benecial, effects of MCT consump-
tion on metabolic risk factors should be examined further.
CONFLICT OF INTEREST
Dr St-Onge is on the Advisory Board of Freelife LLC. The remaining authors declare no
conict of interest.
ACKNOWLEDGEMENTS
We would like to thank all participants for their involvement in this study and Xinyue
Tong and Lilly Nhan for their assistance in the conduct of the study for study 1
participants. MPSO, BM, HRK and BL designed the research; MPSO, BM and MO
conducted research; MPSO, BM and AR analyzed data; MPSO, BM, HRK, BL and AR
wrote the paper; MPSO had primary responsibility for nal content. All authors read
and approved the nal manuscript. This publication was supported by the National
Center for Advancing Translational Sciences, National Institutes of Health, through
Grant Number UL1 TR000040, formerly the National Center for Research Resources,
Grant Number UL1 RR024156, the New York Obesity Nutrition Research Center Grant
Number P30-DK26687. MCT oil was provided by Stepan Company. This trial was
registered on Clinicaltrials.gov, identier NCT01952977.
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Supplementary Information accompanies this paper on European Journal of Clinical Nutrition website (http://www.nature.com/ejcn)
Regulation of appetite by medium chain fatty acids
M-P St-Onge et al
7
© 2014 Macmillan Publishers Limited European Journal of Clinical Nutrition (2014) 1 7
... MCTs, unlike LCTs, have been reported to act on GLP-1 but not on GIP (30). In clinical studies, MCTs ingested before meals were reported to induce a series of physiological changes, including lowered postprandial blood glucose levels, increased insulin secretion, suppression of food intake, and increased GLP-1 levels in the blood (31). MCTs and LCTs were also shown to differ in their effects on stimulation of gastrointestinal hormone secretion, such as ghrelin, CCK, and incretin. ...
... In support of the above mechanism, molecular mechanisms for the downstream effects of ghrelin acylation on protein metabolism have also been reported, including the activation of Akt/mTOR in the liver by ingestion of MCTs (74). Insulin and insulin-like growth factor (IGF-1) are typical mediators of Akt/mTOR, both of which have been reported to be increased by ingestion of MCTs (28,31). In studies using animal models of chronic kidney disease, enhanced muscle protein metabolism, and mitochondrial function were reported (75). ...
... IV. As an indirect effect, MCTs may increase satiety and reduce excessive food intake by activating GLP-1 in the daily diet (29,31,172). ...
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Stephen L. Defelice, founder and chairman of the Foundation of Innovation Medicine, created the term "Nutraceuticals" in 1989 as a combination of the words "nutrition" and "pharmaceutical." Nutraceuticals are food-derived products that are claimed to give additional health advantages in addition to the fundamental nutritional content present in meals. Their kinds may be more significant than their quantity in terms of health and disease. The aim of this review is to provide a summary of the research on the role of functional lipids namely: Omega -6 fatty acid, Omega -3 fatty acid, Conjugated linoleic acid, Medium chain triglycerides and Phytosterols as nutraceuticals in human health. Functional lipids have been related to the prevention and treatment of a variety of ailments, according to new study. With the use of supplementary and dietary forms of functional lipids, scientific data has demonstrated positive improvements in patients and favorable benefits in healthy people. Keywords: Nutraceuticals, Functional lipids, Conjugated linoleic acid, Medium chain triglycerides, Omega -6 fatty acid, Omega -3 fatty acid, Phytosterols
... MCT have been reported to increase satiety (Coleman, Quinn, & Clegg, 2016;Ogawa et al., 2007;Van Wymelbeke, Himaya, Louis-Sylvestre, & Fantino, 1998;Van Wymelbeke, Louis-Sylvestre, & Fantino, 2001) and increase energy expenditure Marten et al., 2006) compared to more commonly consumed long-chain triglycerides (LCT). This is thought to be achieved through rapid absorption due to the smaller molecular weight of MCT (Evans et al., 1998), which not only leads to the entirety of the MCT bolus to be absorbed at the point of ingestion unlike LCT where some remains in the intestine until further consumption (Page et al., 2009), but also the production of ketone bodies such as β-hydroxybutyrate (β-HB) (Laeger, Metges, & Kuhla, 2010), which is thought to be anorexigenic (St-Onge et al., 2014). Food intake is lower after an MCT-rich pre-load compared to an LCT-rich pre-load and that results increased leptin and PYY levels after MCT consumption compared to LCT and decreased active ghrelin compared to LCT, but not GLP-1 or total ghrelin (TG) (Maher et al., 2021). ...
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Medium chain fatty acids (MCFAs) has unique transport system and is rapidly metabolized in the body. It mainly occurs in coconut oil, palm kernel oil and milk products. Dietary supplementation with MCFAs can improve metabolic features as well as cognition in humans. Some of the effects of MCFAs may be through direct receptor-mediated intracellular pathways, but MCFAs are also metabolic regulators that can alter circulating levels of hormones and metabolites, and hence may indirectly mediate body metabolism. Here we describe how dietary medium chain fatty acid, previously found to improve immune response and insulin secretion via G-protein coupled receptors, can increase apoptosis in cancer cells through the activation of the EGFR/ERK/AP1 trans-duction pathway. MCFA-enriched diets could therefore be used to manage metabolic diseases through the modification of gut microbiota, activation of GPR 40 and GPR 84.
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Objectives The aim of this study is to compare acute effects of consuming extra virgin coconut oil (EVCO) as a source of medium chain fatty acids and extra virgin olive oil (EVOO) as a source of long chain fatty acids in normal weight and obese subjects. Design Randomised, crossover design. Participants Metabolically healthy twenty male subjects (10 normal weight; 10 obese) aged 19–40 years. Intervention Subjects consumed breakfast meals containing skimmed milk, fat-free white cheese, bread and EVCO (25 g) or EVOO (25 g). Outcome measures Visual analog scale evaluations, resting metabolic rate measurements and selected blood parameters analysis (glucose, triglyceride, insulin and plasma peptide YY) were performed before and after the test breakfast meals. In addition, energy intakes were evaluated by ad libitum lunch meal at 180 min. Results Visual analogue scale values of hunger and desire to eat decreased significantly after EVCO consumption than EVOO consumption in normal weight subjects at 180 min. There was an increase trend in plasma PYY at 30 and 180 min after EVCO breakfast compared to EVOO breakfast. Ad libitum energy intakes after EVCO and EVOO consumption in normal weight subjects were 924 ± 302; 845 ± 158 kcal (p = 0.272), respectively whereas in obese subjects were 859 ± 238; 994 ± 265 kcal (p = 0.069) respectively. Conclusion The results of this study shows that consumption of EVCO compared to EVOO may have suppressive effect on hunger and desire to eat, may affect postprandial PYY levels differently and have no effect on postprandial energy expenditure. Trial registration Clinical Trials NCT04738929 .
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The present work explored the effect of using ultrasound during synthesis of oleogels on stability, strength and oxidative stability of oleogel and its comparison with conventional stirring process to highlight the importance of using ultrasound. Further, this MCT-based oleogel was used in formulation of cookies and its effect on texture and sensory attributes was examined. Ethyl cellulose (EC) concentration of 1.5% at ≤10 °C during synthesis resulted in gelation of MCT liquid oil. Ultrasound duty cycle of 10% and 20 kHz frequency improved the elastic modulus (G’) of oleogel and reduced the oil loss when maintained for storage period of 30 days and also the U-MCTO showed excellent hardness and stickiness for 30 days as compared with the oleogel prepared using conventional stirring. The U-MCTO, C-MCTO and MCT liquid oil showed induction time of 9.76, 6.41, 5.98 h at 110 °C, thus showing higher oxidative stability for the U-MCTO at accelerated conditions. The U-MCTO cookies showed excellent texture with force (N) of 4.17 ± 0.01 and 4.73 ± 0.00 N on 0 and 30 days, respectively, whereas it was much higher for MCTLO cookies i.e., 5.2 ± 0.0 and 7.89 ± 0.00 N on 0 and 30 days, respectively, making it unsuitable for consumption. The sensory score and overall acceptability of U-MCTO cookies was higher in terms of texture, mouthfeel, crunchiness, and hardness making it an excellent replacement for the use of saturated fat in bakery application like cookies.
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Medium chain triglycerides (MCT) are esters of fatty acids with 6 to 12 carbon atom chains. Naturally, they occur in various sources; their composition and bioactivity are source and extraction process-linked. The molecular size of MCT oil permits unique metabolic pathways and energy production rates, making MCT oil a high-value functional food. This review details the common sources of MCT oil, presenting critical information on the various approaches for MCT oil extraction or synthesis. Apart from conventional techniques, non-thermal processing methods that show promising prospects are analyzed. The biological effects of MCT oil are summarized, and the range of need-driven modification approaches are elaborated. A section is devoted to highlighting the recent trends in the application of MCT oil for food, nutraceuticals, and allied applications. While much is debated about the role of MCT oil in human health and wellness, there is limited information on daily requirements, impact on specific population groups, and effects of long-term consumption. Nonetheless, several studies have been conducted and continue to identify the most effective methods for MCT oil extraction, processing, handling, and storage. A knowledge gap exists and future research must focus on technology packages for scalability and sustainability.
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The present study aimed to evaluate the varied sonication amplitudes (60–100%) on the physicochemical properties of medium-chain triglyceride (MCT)-based and long-chain triglyceride (LCT)-based in curry gravy. This work also aimed to determine the effects of the sonicated curry gravy at optimum amplitude and in-vitro lipid digestibility as the potential indication of satiation perception. Curry gravy was chosen as food model in this study as it is one of the most preferred meals in South-East Asia countries. The application of sonication treatment significantly reduced (p < 0.05) the droplet size of MCT-based curry gravy from 119 μm to the smallest 29 μm (sonicated at 80%) and LCT-based curry gravy from 132.5 μm to the smallest 29 μm (sonicated at 70%). Sonication treatment increased the lightness of MCT-based and LCT-based curry gravy from 33.67 to 52.10 and 33.50 to 50.50, respectively. The increase of sonication amplitudes increased the consistent flow index of MCT-based (from 0.05 to range 0.24–0.60) and LCT-based curry (from 0.05 to range 0.20–0.27). All sonicated samples exhibited shear-thinning behaviour. The rate of fatty acid released during in vitro lipid digestibility increased by at least 30% for both MCT-based and LCT-based curry gravy after sonication at 80% amplitude. Results obtained indicate effectiveness of sonication in potentially prolonging satiation perception by producing small fat globule droplets size, more even and stable emulsion with greater viscosity independent of the fatty acid chain length (MCT or LCT). It provides useful information in developing food emulsion system with enhanced satiating power predominantly in appetite control.
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Context: The relationship between postprandial peptides at circulating physiological levels and short-term appetite control is not well understood. Objective: The purpose of this study was first to compare the postprandial profiles of ghrelin, glucagon-like peptide 1 (GLP-1), and peptide YY (PYY) after isoenergetic meals differing in fat and carbohydrate content and second to examine the relationships between ghrelin, GLP-1, and PYY with hunger, fullness, and energy intake. Design: Plasma was collected before and periodically after the meals for 180 minutes, after which time ad libitum food was provided. Simultaneous ratings of hunger and fullness were tracked for 180 minutes through phases identified as early (0-60 minutes) and late (60-180 minutes) satiety. Setting: This study was conducted at the Psychobiology and Energy Balance Research Unit, University of Leeds. Participants: The participants were 16 healthy overweight/obese adults. Main outcome measures: Changes in hunger and fullness and metabolic markers were indicators of the impact of the meals on satiety. Results: Ghrelin was influenced similarly by the 2 meals [F(1, 12) = 0.658, P = .433] and was significantly associated with changes in hunger (P < .05), which in turn correlated with food intake (P < .05). GLP-1 and PYY increased more by the high-fat meal [F(1, 15) = 5.099 and F(1, 14) = 5.226, P < .05]. GLP-1 was negatively associated with hunger in the late satiety phase and with energy intake (P < .05), but the PYY profile was not associated with hunger or fullness, nor was PYY associated with food intake. Conclusions: The results demonstrate that under these conditions, these peptides respond differently to ingested nutrients. Ghrelin and GLP-1, but not PYY, were associated with short-term control of appetite over the measurement period.
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Background: Breakfast skipping is a common dietary habit practiced among adolescents and is strongly associated with obesity. Objective: The objective was to examine whether a high-protein (HP) compared with a normal-protein (NP) breakfast leads to daily improvements in appetite, satiety, food motivation and reward, and evening snacking in overweight or obese breakfast-skipping girls. Design: A randomized crossover design was incorporated in which 20 girls [mean ± SEM age: 19 ± 1 y; body mass index (in kg/m2): 28.6 ± 0.7] consumed 350-kcal NP (13 g protein) cereal-based breakfasts, consumed 350-kcal HP egg- and beef-rich (35 g protein) breakfasts, or continued breakfast skipping (BS) for 6 d. On day 7, a 10-h testing day was completed that included appetite and satiety questionnaires, blood sampling, predinner food cue–stimulated functional magnetic resonance imaging brain scans, ad libitum dinner, and evening snacking. Results: The consumption of breakfast reduced daily hunger compared with BS with no differences between meals. Breakfast increased daily fullness compared with BS, with the HP breakfast eliciting greater increases than did the NP breakfast. HP, but not NP, reduced daily ghrelin and increased daily peptide YY concentrations compared with BS. Both meals reduced predinner amygdala, hippocampal, and midfrontal corticolimbic activation compared with BS. HP led to additional reductions in hippocampal and parahippocampal activation compared with NP. HP, but not NP, reduced evening snacking of high-fat foods compared with BS. Conclusions: Breakfast led to beneficial alterations in the appetitive, hormonal, and neural signals that control food intake regulation. Only the HP breakfast led to further alterations in these signals and reduced evening snacking compared with BS, although no differences in daily energy intake were observed. These data suggest that the addition of breakfast, particularly one rich in protein, might be a useful strategy to improve satiety, reduce food motivation and reward, and improve diet quality in overweight or obese teenage girls. This trial was registered at clinicaltrials.gov as NCT01192100.
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Several carbohydrate-based models of feeding have been described. The influence of the substrate oxidation rate on liking, wanting, and macronutrient selection, however, is not known in humans. The aim of this study was to investigate the influence of the substrate oxidation rate on the above variables. A randomized 4-condition study was conducted in 16 normal-weight men (mean ± SD age: 23 ± 3 y). The sessions differed in the composition of breakfast, which was either high in carbohydrates (HC) or low in carbohydrates (LC) or high in fat (HF) or low in fat (LF). Two hours and 20 minutes after breakfast, energy expenditure (EE) and respiratory exchange ratios (RERs) were measured. Next, olfactory liking for 4 foods (sweet and fatty) and ad libitum energy intake (carbohydrate- and fat-rich bread) were evaluated. EE was higher (P < 0.001) and subsequent intake was lower (P < 0.01) after the HC and HF breakfasts than after the LC and LF breakfasts. The HC and LC breakfasts induced a higher RER (P < 0.001), lower olfactory liking for sweet foods (P < 0.05), and the consumption of a lower proportion of carbohydrate-rich bread (P< 0.05) than did the HF and LF breakfasts. The HF breakfast induced the lowest RER (P < 0.001), the lowest olfactory liking for fatty foods (P < 0.05), and the lowest proportion of fat-rich bread consumed (P < 0.01). Above all, a negative correlation was found between the RER and olfactory liking for sweet foods (P < 0.001). A high fat oxidation rate induces a strong liking for carbohydrates and a low liking for fats, which lends new support to the carbohydrate-based model of feeding. This trial is registered at clinicaltrials.gov as NCT01122082.
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Background and aims: Compared to long chain triglycerides (LCT), medium chain triglycerides (MCT) are considered an attractive caloric source in malabsorptive diseases because of their favorable physico-chemical characteristics. The use of MCTis, however, limited by the occurrence of gastrointestinal symptoms such as diarrhoea. We have, therefore, investigated the effects of MCT and LCT on proximal (cholecystokinin; CCK) and distal (peptide YY; PYY) gut hormone secretion. Methods: Eight healthy volunteers participated in four experiments performed in random order during continuous intraduodenal administration for 360 min of a) saline (control); b) LCT15 mmol/h; c) MCT15mmol/h (equimolar); d) MCT 30 mmol/h (equicaloric). Plasma CCK and PYY were determined at regular intervals (radioimmunoassay). Duodenocecal transit (DCTT) was measured by lactulose H(2)breath test. Results: DCTT during LCT (105 +/- 11 min) was not significantly different from saline (111 +/- 10 min). Both low dose MCT (54 +/- 5 min) and high dose MCT (61 +/- 6 min) significantly accelerated DCTT (P< 0.05). Plasma CCK increased significantly (P< 0.05) during LCT but not during MCT or saline. PYY increased significantly (P< 0.05) not only during LCT, but also during low and high dose MCT but not during saline. Conclusions: Intraduodenal MCTs a) accelerate intestinal transit; b) do not stimulate CCK release; c) but stimulate release of the distal gut hormone PYY. These results suggest that MCTs are not rapidly absorbed in the proximal gut but probably reach the ileocolonic region and stimulate PYY release.
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Meals high in protein induce greater intermeal satiety than meals high in fat and carbohydrates. We studied the gut hormone response and subsequent food intake after breakfasts high in protein, carbohydrate or high in fat controlled for volume, calories and appearance. Eight healthy volunteers participated in this randomized three-way crossover study. Study breakfasts were calculated to provide 20% of daily energy requirements and provided either 60% of energy from protein, fat or carbohydrate. Blood was drawn half-hourly for 4 h; energy intake at a subsequent ad libitum meal was measured. Total ghrelin decreased after food intake equally with the three breakfasts. PYY levels were highest after the high protein breakfast (P = 0.005). Indeed, PYY at 240 min was highest after the high protein breakfast compared to the high fat breakfast and to the high carbohydrate breakfast (P = 0.011 and P = 0.012, respectively). GLP-1 levels were highest after the high protein breakfast (P = 0.041) at 120 min and remained higher throughout the study. These differences in gut hormones did not translate into differences in food intake (1023 ± 390 kcal after high protein, 1016 ± 388 kcal after high fat and 1158 ± 433 kcal after high carbohydrate). We conclude that a high protein meal increases circulating concentrations of the gut hormones PYY and GLP-1, but when meals are matched for volume, appearance and caloric value, these gut hormone changes do not translate into a reduction in ad libitum food intake.
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The objective of these 4 studies was to describe the effects of protein source, time of consumption, quantity, and composition of protein preloads on food intake in young men. Young men were fed isolates of whey, soy protein, or egg albumen in sweet and flavored beverages (400 mL) and provided a pizza meal 1-2 h later. Compared with the water control, preloads (45-50 g) of whey and soy protein, but not egg albumen, suppressed food intake at a pizza meal consumed 1 h later. Meal energy intake after egg albumen and soy, but not after control or whey treatments, was greater when the treatments were given in the late morning (1100 h) compared with earlier (0830-0910 h). Suppression of food intake after whey protein, consumed as either the intact protein or as peptides, extended to 2 h. Altering the composition of the soy preload (50 g) by reducing the soy protein content to 25 g and by adding 25 g of either glucose or amylose led to a loss in suppression of food intake by the preload. Egg albumen, in contrast to whey and soy preloads, increased cumulative energy intake (sum of the energy content of the preload plus that in the test meal) relative to the control. We conclude that protein source, time of consumption, quantity, and composition are all factors determining the effect of protein preloads on short-term food intake in young men.
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Cells, tissues and organisms have the ability to rapidly switch substrate oxidation from carbohydrate to fat in response to changes in nutrient intake, and to changes in energy demands, environmental cues and internal signals. In healthy, metabolically normal individuals, substrate switching occurs rapidly and completely; in other words, substrate switching is 'flexible'. A growing body of evidence demonstrates that a blunted substrate switching from low- to high-fat oxidation exists in obese individuals, as well as in pre-obese and post-obese, and that this 'metabolic inflexibility' may be a genetically determined trait. A decreased fat oxidation can lead to a positive energy balance under conditions of high-fat feeding, due to depletion of glycogen stores that stimulates appetite and energy intake through glucostatic and glucogenostatic mechanisms, e.g. hepatic sensing of glycogen stores. Several genetic polymorphisms and single-nucleotide polymorphisms have been identified that are associated with low-fat oxidation rates and metabolic inflexibility, and genetic identification of susceptible individuals may lead to personalized prevention of weight gain using fat oxidation stimulants ('fat burners') in the future.
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High-fat diets are associated with obesity, and the weak satiety response elicited in response to dietary lipids is likely to play a role. Preliminary evidence from studies of medium (MCT) and long chain triglycerides (LCT) supports greater appetite suppression on high-MCT diets, possibly a consequence of direct portal access, more rapid oxidation and muted lipaemia. No data is as yet available on high-SCT diets which also have direct hepatic access. In this study SCT- (dairy fats), MCT- (coconut oil) and LCT-enriched (beef tallow) test breakfasts (3.3 MJ) containing 52 g lipid (58 en% fat) were investigated in a randomized, cross-over study in 18 lean men. All participants were required to complete the 3 study days in randomised order. Participants rated appetite sensations using visual analogue scales (VAS), and energy intake (EI) was measured by covert weighing of an ad libitum lunch meal 3.5 h postprandially. Blood samples were collected by venous cannulation. There were no detectable differences between breakfasts in perceived pleasantness, visual appearance, smell, taste, aftertaste and palatability (P>0.05). There was no significant effect of fatty acid chain length on ratings of hunger, fullness, satisfaction or current thoughts of food, nor did energy (mean, sem: SCT: 4406, 366 kJ; MCT: 4422, 306 kJ; LCT: 4490, 324 kJ; P>0.05) or macronutrient intake at lunch differ between diets. The maximum difference in EI between diets was less than 2%. Postprandial lipaemia also did not differ significantly. We conclude that there was no evidence that fatty acid chain length has an effect on measures of appetite and food intake when assessed following a single high-fat test meal in lean participants.
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We hypothesized that consuming eggs for breakfast would significantly lower postprandial satiety and energy intake throughout the day. Using a crossover design, 21 men, 20 to 70 years old, consumed 2 isoenergetic test breakfasts, in a random order separated by 1 week. The macronutrient composition of the test breakfasts were as follows: (EGG, % CHO/fat/protein = 22:55:23) and (BAGEL, % CHO/fat/protein = 72:12:16). Fasting blood samples were drawn at baseline before the test breakfast and at 30, 60, 120, and 180 minutes after breakfast. After 180 minutes, subjects were given a buffet lunch and asked to eat until satisfied. Subjects filled out Visual Analog Scales (VAS) during each blood draw and recorded food intake the days before and after the test breakfasts. Plasma glucose, insulin, and appetite hormones were analyzed at each time point. Subjects consumed fewer kilocalories after the EGG breakfast compared with the BAGEL breakfast (P< .01). In addition, subjects consumed more kilocalories in the 24-hour period after the BAGEL compared with the EGG breakfast (P < .05). Based on VAS, subjects were hungrier and less satisfied 3 hours after the BAGEL breakfast compared with the EGG breakfast (P < .01). Participants had higher plasma glucose area under the curve (P < .05) as well as an increased ghrelin and insulin area under the curve with BAGEL (P < .05). These findings suggest that consumption of eggs for breakfast results in less variation of plasma glucose and insulin, a suppressed ghrelin response, and reduced energy intake.