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International Journal of Food Sciences and Nutrition
ISSN: 0963-7486 (Print) 1465-3478 (Online) Journal homepage: http://www.tandfonline.com/loi/iijf20
Chili pepper as a body weight-loss food
Sharon Varghese, Peter Kubatka, Luis Rodrigo, Katarina Gazdikova, Martin
Caprnda, Julia Fedotova, Anthony Zulli, Peter Kruzliak & Dietrich Büsselberg
To cite this article: Sharon Varghese, Peter Kubatka, Luis Rodrigo, Katarina Gazdikova, Martin
Caprnda, Julia Fedotova, Anthony Zulli, Peter Kruzliak & Dietrich Büsselberg (2016): Chili
pepper as a body weight-loss food, International Journal of Food Sciences and Nutrition, DOI:
10.1080/09637486.2016.1258044
To link to this article: http://dx.doi.org/10.1080/09637486.2016.1258044
Published online: 29 Nov 2016.
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COMPREHENSIVE REVIEW
Chili pepper as a body weight-loss food
Sharon Varghese
a
, Peter Kubatka
b
, Luis Rodrigo
c
, Katarina Gazdikova
d,e
, Martin Caprnda
f
,
Julia Fedotova
g,h,i
, Anthony Zulli
j
, Peter Kruzliak
k,l
and Dietrich B€
usselberg
a
a
Weill Cornell Medicine in Qatar, Qatar Foundation-Education City, Doha, Qatar;
b
Department of Medical Biology, Jessenius Faculty of
Medicine, Comenius University in Bratislava, Martin, Slovakia;
c
Department of Gastroenterology, Faculty of Medicine, University of
Oviedo, Central University Hospital of Asturias (HUCA), Oviedo, Spain;
d
Department of Nutrition, Faculty of Nursing and Professional
Health Studies, Faculty of Medicine, Slovak Medical University, Bratislava, Slovakia;
e
Department of General Medicine, Faculty of
Medicine, Slovak Medical University, Bratislava, Slovakia;
f
2nd Department of Internal Medicine, Faculty of Medicine, Comenius
University and University Hospital, Bratislava, Slovakia;
g
Laboratory of Neuroendocrinology, I.P. Pavlov Institute of Physiology, Russian
Academy of Sciences, St. Petersburg, Russia;
h
Laboratory of Comparative Somnology and Neuroendocrinology, I.M. Sechenov Institute
of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia;
i
International Research Centre
Biotechnologies of the Third Millennium, ITMO University, St. Petersburg, Russia;
j
Centre for Chronic Disease, College of Health and
Biomedicine, Victoria University, Werribee, Australia;
k
Department of Chemical Drugs, Faculty of Pharmacy, University of Veterinary
and Pharmaceutical Sciences, Brno, Czech Republic;
i
Department of Surgery, Center for Vascular Disease, St. Anne’s University
Hospital, Faculty of Medicine, Masaryk University, Brno, Czech Republic
ABSTRACT
Chili has culinary as well as medical importance. Studies in humans, using a wide range of doses
of chili intake (varying from a single meal to a continuous uptake for up to 12 weeks), concluded
that it facilitates weight loss. In regard to this, the main targets of chili are fat metabolism, energy
expenditure, and thermogenesis. To induce weight loss, the active substance of chili, capsaicin,
activates Transient Receptor Potential Cation Channel sub-family V member 1 (TRPV1) channels)
receptors causing an increase in intracellular calcium levels and triggering the sympathetic ner-
vous system. Apart from TRPV1, chili directly reduces energy expenditure by activating Brown
Adipose Tissue. Weight loss by chili is also the result of an improved control of insulin, which
supports weight management and has positive effects for treatment for diseases like obesity, dia-
betes and cardiovascular disorders. This review summarizes the major pathways by which chili
contributes to ameliorating parameters that help weight management and how the consumption
of chili can help in accelerating weight loss through dietary modifications.
ARTICLE HISTORY
Received 10 August 2016
Revised 1 November 2016
Accepted 3 November 2016
KEYWORDS
Chili pepper; weight loss;
appetite; energy balance
Chili and health
Chili is a widely used flavoring spice and is culturally
prominent in diets of various communities and cul-
tures around the world since 7000BC (Kraft et al.
2014). In chili, more than 200 constituents have been
identified and some of its active constituents play
numerous beneficial roles in the human organism.
The major active compounds of chili are the pungent
capsaicinoids (capsaicin and dihydrocapsaicin), which
give a hot sensation when consumed. Capsinoids, which
are non-pungent capsaicin analogs (capsiate, dihydro-
capsiate, and nordihydrocapsiate), are substances also
naturally present in chili peppers. Those peppers also
contain other components like antioxidants, vitamins,
and carotenoids (Maji & Banerji 2016).
Most attention is given to capsaicin especially in
regard its ability to modulate pain (Zhang & Li Wan Po
1994), e.g. by interacting with TRPV1 receptor channel
complex allowing calcium to enter the cytosol (Satheesh
&B
€
usselberg 2015). Apart from the treatment of pain
inflammation, capsaicin is considered as an appropriate
substance applicable in the add-on therapy of rheuma-
toid arthritis (Richards et al. 2012), cluster headaches
(Matharu 2010), herpes zoster (Jeon 2015), and vaso-
motor rhinitis (Singh & Bernstein 2014).
The other main area of research investigates the
effects of chili intake on cardiovascular parameters
like heart rate, Subendocardial Viability Ratio (SEVR)
and Calcitonin Gene Related Peptide (CGRP). While
beneficial effects were reported (e.g. heart attacks and
CONTACT Peter Kruzliak kruzliakpeter@gmail.com Department of Chemical Drugs, Faculty of Pharmacy, University of Veterinary and
Pharmaceutical Sciences, Palackehotr 1946/1, 612 42 Brno, Czech Republic; Dietrich B€
usselberg dib2015@qatar-med.cornell.edu Weill Cornell
Medicine in Qatar, Qatar Foundation-Education City, POB 24144, Doha, Qatar; Katarina Gazdikova katarina.gazdikova@szu.sk Department of
Nutrition, Faculty of Nursing and Professional Health Studies, Faculty of Medicine, Slovak Medical University, Limbova 12, 833 03 Bratislava, Slovakia
Author's Agreement: The manuscript is approved by all named authors and the order of authors listed in the manuscript has been approved by all authors.
ß2016 Informa UK Limited, trading as Taylor & Francis Group
INTERNATIONAL JOURNAL OF FOOD SCIENCES AND NUTRITION, 2016
http://dx.doi.org/10.1080/09637486.2016.1258044
long-term tachycardia were reduced; a higher CGRP
contributing to vasodilation helped to combat arterial
blocks, Yoshioka et al. 2001; Ahuja & Ball 2006; Yuan
et al. 2015) other parameters like arterial stiffness,
inflammation, or oxidative stress biomarkers (Nieman
et al. 2012) were unchanged. Moreover, capsaicinoids
significantly decreased serum total cholesterol, low-
density lipoprotein cholesterol, and tri-acylglycerols
without affecting the high-density lipoprotein choles-
terol in the animal model. This effect was caused by
the stimulating conversion of cholesterol to bile acids
(Zhang et al. 2016). Chili demonstrated beneficial
effects in various gastrointestinal disorders such as
stimulation of digestion and gastro-mucosal defense,
reduction of gastroesophageal reflux disease symp-
toms, inhibition of gastrointestinal pathogens, ulcer-
ation and cancers, regulation of gastrointestinal
secretions, and absorptions (Maji & Banerji 2016).
Furthermore, capsaicin has proven an effective anti-
cancer agent. Several up-to-date preclinical studies
reported that capsaicin may suppress various human
neoplasia by generating reactive oxygen species and
increasing apoptosis (Sarkar et al. 2015; Liu et al.
2016; Zheng et al. 2016). Finally, capsaicin demon-
strated significant antioxidant and metal-binding
properties and therefore it was postulated that this
compound has important implications in the preven-
tion or treatment of neurodegenerative diseases such
as Alzheimer’s disease (Dairam et al. 2008).
This review focuses on a less highlighted aspect, in
particular how chili intake influences parameters
known to reduce body weight and how they are modi-
fied by the consumption of chili. A widespread health
concern is the large number of adults and children of
developed societies who are overweight. The World
Health Organization (WHO) (2014) reports that at
least 1.9 billion adults, 18 years and older, are over-
weight, and of those more than 600 million are obese
(Body Mass Index –BMI above 30). Data show that
in 2011–2012, 16.9%of youth and 34.9%of adults in
the United States suffer from obesity (Ogden et al.
2014). Overweight and obesity result in heart disease,
diabetes, reduced longevity, psychological, and social
acceptance issues to name just a few.
Multiple approaches to reduce weight or stop gain-
ing weight, such as changes in lifestyle including phys-
ical exercise (U.S. Department of Health and Human
Services 2008) and diet control are most commonly
used to manage weight (Nurkkala et al. 2015).
Here, we summarize how dietary chili intake influ-
ences parameters such as metabolism or insulin levels
which directly or indirectly influence the energy
balance and therefore body weight (overview in
Figure 1).
Effects of chili on body weight
Overweight and obesity develop when the energy
intake (food consumption) exceeds the energy used by
the body. When the energy intake (EI) exceeds the
energy expenditure (EE) it is defined as a positive
energy balance. Measures to increase the expenditure
or reduce the intake are adopted for weight manage-
ment programs (Hill et al. 2012) along with elevating
“diet induced thermogenesis”(DIT) to change the
energy balance. Recent reviews (Ludy & Mattes 2011;
Whiting et al. 2014) showed strong evidence for sig-
nificant and positive effects of chili consumption in
aggravating energy metabolism. Unfortunately, not
many studies analyze how parameters like dosage of
chili, age group, ethnicity, weight, etc. are related to
intake of chili.
The following chapters give an overview of how
rates of oxidation, respiratory measurements, thermo-
genesis, energy expenditure and intake, appetite, and
insulin regulation are modified by chili consumption
under experimental and clinical settings (Tables 1
and 2).
Effect on rates of oxidation of lipids and
lipoproteins
Capsaicin has been reported to increase energy
expenditure and diet-induced thermogenesis probably
due to b-adrenergic stimulation and a decrease in the
respiratory quotient, implying a shift in substrate oxi-
dation from carbohydrate to fat oxidation (Ludy &
Mattes 2011; Smeets et al. 2013; Shook et al. 2015).
Reduced lipoprotein oxidation and increased lipid oxi-
dation supports weight loss (Vasankari et al. 2001;
Berggren et al. 2008). This is asserted by lowered rate
of serum lipoprotein oxidation observed upon add-
ition of chili to diet. In women, a lag of this rate was
observed, which might be explained by a higher
amount of chili or capsaicin available per kg of body
weight. The study concluded that regular consumption
of chili resists serum lipoprotein oxidation (Ahuja &
Ball 2006). Addition of chili increased lipid oxidation
postprandial more in a high fat (HF) than a high
carbohydrate (HC) meal. Chili when consumed with
caffeine decreased lipid oxidation immediately after
the meal, whereas it increased when the subjects were
asleep (Yoshioka et al. 2001). Inclusion of capsaicin
was shown to maintain fat oxidation rates compared
with placebo (Lejeune et al. 2003). Addition of chili
2 S. VARGHESE ET AL.
postprandial decreased carbohydrate oxidation
(Yoshioka et al. 1998). Conversely, an increased carbo-
hydrate oxidation was reported in runners after the
consumption of chili, although this was not due to
increased energy expenditure (Lim et al. 1997). In a
recent study, Ohyama et al. (2015) examined whether
the beneficial effects of exercise could be enhanced by
capsinoids supplementation in mice. The combination
of exercise and capsinoid supplementation robustly
improved metabolic profiles, including the plasma
cholesterol level and significantly activated both the
oxidative phosphorylation and fatty acid oxidation in
skeletal muscle. This combination increased cyclic
Adenosine Mono-Phosphate (cAMP) levels and pro-
tein kinase A activity in brown adipose tissue, indicat-
ing an increase of lipolysis (Ohyama et al. 2015).
Moreover, this combination prevented diet-induced
liver steatosis and decreased the size of adipocyte cells
Table 1. Parameters influenced by chili consumption.
Factors affected Conclusion from studies References
Rates of oxidation Improved, even with non-pungent spices,
caffeine and green tea
Yuan et al. (2015), Zheng et al. (2016), Lee et al. (2015), Ahuja and
Ball (2006), and Snitker et al. (2009)
RQ and RER Decreased RQ and Increased RER Yuan et al. (2015), Zheng et al. (2016), Smeets et al. (2013), and Ludy
and Mattes (2011)
DIT & Energy Expenditure Improved DIT and increase by up to 30% Yuan et al. (2015), Zheng et al. (2016), Ohyama et al. (2015), Smeets
et al. (2013), and Ludy and Mattes (2011)
Energy intake Reduced intake of fat and protein uptake Yuan et al. (2015), Zhang et al. (2016), and Reyes-Escogido et al.
(2011)
Appetite and satiety Reduced ghrelin levels Yuan et al. (2015), Zheng et al. (2016a, b), Smeets et al. (2013),
Smeets and Westerterp-Plantenga (2009), Ludy and Mattes (2011),
and Janssens et al. (2013)
Insulin Reduced blood glucose and increased
glucose tolerance
Li et al. (2014), Ahuja et al. (2007), Kraft et al. (2014), Larsen (2008),
Islam and Choi (2008), and Chen et al. (2015)
Figure 1. Overview of the pathways activated by chili consumption. The figure highlights the parameters affected by chili
(PURPLE), i.e. capsaicin and capsinoids (non-pungent), contributing to weight (TEAL) management. The RED pathway shows the
components of oxidative processes that directly involve in reducing the amount of fat available. The ORANGE pathway highlights
the activation and effects on brown adipose tissue (BAT) with the consumption of chili. Finally, the BLUE pathway combines the
mechanisms activated by chili under the control of the sympathetic nervous system, i.e. TRPV1 receptors, appetite, hormonal man-
agement of Insulin and Ghrelin. The pathways together summarize how and where in the body chili has the most effective regula-
tion in the management of weight.
INTERNATIONAL JOURNAL OF FOOD SCIENCES AND NUTRITION 3
in white adipose tissue. In another study, using obese
diabetic KKAy mice, dietary capsaicin increased the
expression of the adiponectin gene/protein and its
receptor (AdipoR2) in adipose tissue and/or plasma,
and these changes were accompanied by increased
activation of hepatic AMP-activated protein kinase, a
marker of fatty acid oxidation (Kang et al. 2011).
The fact that capsiate administration contributes to
the enhancement of aerobic ATP production and the
reduction of body fat content in rats (through a skel-
etal muscle mitochondrial uncoupling protein-3 gene
downregulation) was also confirmed (Faraut et al.
2009).
Chili increases fat oxidation and reduces triglycer-
ide accumulation, which is the main constituent of
body fat (pathway illustrated in RED in Figure 1).
Thus, their reduction can contribute to ameliorating
weight gain. Free fatty acids are formed by lipolysis of
triglycerides. Triglycerides are a target of the uncou-
pling protein 1 (UCP-1), which when upregulated and
in conjunction with Sympathetic Nervous System
(SNS) activation, causes thermogenesis (Figure 1). The
inclusion of chili in the diet primarily activates
TRPV1 receptors and triggers a number of pathways
that can result in a more efficient weight management.
TRPV1 increases [Ca
2þ
]
i
reducing adipogenesis and
reduced lipid accumulation (Figure 1; RED pathway).
This increase of [Ca
2þ
]
i
is mediated through
Connexin 43 (Cx 43). The upregulation of Cx 43
improves adipocyte-to-adipocyte communication
resulting in lipolysis and thus contributing to reduc-
tion in body fat and consequently weight loss (Chen
et al. 2015).
Interestingly the ingestion of non-pungent capsi-
noid also resulted in a significant increase in fat oxida-
tion (Snitker et al. 2009).
Effect on RQ and RER
The respiration quotient (RQ) and respiratory
exchange ratio (RER) are values to determine the
amount of CO
2
exhaled to oxygen. They are identical
at the resting state (Farlex Partner Medical Dictionary
2012). RQ is used for determining Basal Metabolic
Rate and measures the overall metabolism. The RER
helps in determining RQ as well as the fuel (carbohy-
drate or fat) used for metabolism at steady state. RER
is higher (Valtue~
na et al. 1997) and RQ is reduced
(Hainer et al., 2000) when losing weight. RQ is
inversely proportional to fat oxidation while reducing
triglyceride accumulation thereby contributing to
weight loss. Postprandial RQ was reduced by 30%
after a meal containing chili (Yoshioka et al. 2004;
Smeets et al. 2013). Reduced RQ was observed in diet-
ary consumption of chili among habitual users and
non-users of chili (Ludy & Mattes 2011). On the con-
trary, capsinoids administered in four doses (1, 3, 6,
and 12 mg) to 13 healthy subjects did not affect meta-
bolic rate and respiratory quotient when measured 2 h
after exposure. Authors suggested that longer exposure
and higher capsinoids doses may be required to cause
meaningful acute effects on energy metabolism
(Galgani et al. 2010). Another study investigated the
24 h effects of capsaicin on energy expenditure and
substrate oxidation during 25%negative energy bal-
ance. Capsaicin decreased the RQ in human subjects
with 75%of their daily energy requirements compared
to subjects without negative energy balance (Janssens
et al. 2013). Authors concluded that the consumption
of 2.56 mg capsaicin per meal in humans supported
negative energy balance by counteracting the unfavor-
able negative energy balance effect of decrease in com-
ponents of energy expenditure. One study reported
different results (an increase in RQ with the consump-
tion of chili), but, it remains unclear whether this
might be due to the fact that they specifically made
this investigation with "runners" (Lim et al. 1997). An
elevation of RER was also observed when chili and
caffeine were consumed simultaneously (Yoshioka
et al. 2001).
Chili elevates thermogenesis and energy
expenditure
Between regular users and non-chili users, EE
increased more in non-chili users when chili was eaten
Table 2. Metabolic effects of chili consumption under experimental conditions.
Study performed Participants Dose of chili used Observations Conclusions
Kang et al. (2010) Male C57BL/6 mice 0.015% capsaicin for 10 weeks –Enhanced expression of adiponectin
and receptor
–Decreased fasting glucose/insulin
levels
–decreased triglyceride levels
Reduced metabolic
dysregulation
Ohyama et al. (2015) C57BL/6J mice 0.3% capsinoids –Increased cAMP levels and PKA
activity in BAT
Increased Energy expenditure
via activation off at
oxidation
Islam Choi (2008) Sprague–Dawley rats 0.5% and 2% red chili –Increased serum insulin concentration Insulinotrophic action
4 S. VARGHESE ET AL.
(Matsumoto et al. 2000; Ludy & Mattes 2011). Chili
consumed simultaneously with caffeine or green tea
also increased EE (Yoshioka et al. 2001; Reinbach
et al. 2009). A reduced EE after a chili meal was noted
in subjects with BMI 26 and it was suggested that
this could be due to reduced postprandial insulin lev-
els (Ahuja et al. 2006).
Seven healthy volunteers were fed a breakfast con-
taining chili and medium-chain triglycerides (MCT)
oil, chili and sunflower oil, bell pepper and sunflower
oil or bell pepper, and MCT oil. Adding chili and
MCT to meals increased Diet Induced Thermogenesis
(DIT) by over 50%in observed subjects. Authors con-
cluded that this effect may cumulate to help induce
weight loss and prevent weight gain or regain (Clegg
et al. 2013). It has been documented that chili con-
sumption increases DIT in a HC and HF diet
(Yoshioka et al. 1998,2004) but was more pronounced
in persons who generally did not use chili in their diet
(Ludy & Mattes 2011). The core body temperature
increased after chili and CH-19 Sweet consumption by
0.02 C, independent of whether the persons were
regular chili users or not (Ohnuki et al. 2001; Ludy &
Mattes 2011). The largest changes were recorded
10–60 min after intake (Ohnuki et al. 2001). But, on
the contrary, chili could also reduce the core body
temperature (Chatsantiprapa et al. 2014) and the skin
temperature (Ludy & Mattes 2011). The temperature
drop depends on the form of chili that was consumed,
i.e. capsule form or chili as a whole. These differences
might be the result of variations between individuals
as they are not easily explained.
Chili affects energy expenditure by triggering the
Brown Adipose Tissue (BAT) in the same way as low
temperature does, leading to increased energy expend-
iture via non-shivering thermogenesis through TRPV1
channels (Saito & Yoneshiro 2013; Saito 2014).
Thermogenesis is achieved through two pathways,
which increase uncoupled mitochondrial respiration
and secretion of catecholamine from the adrenal
medulla (Westerterp-Plantenga et al. 2006; Reyes-
Escogido et al. 2011). The consumption of a non-pun-
gent compound of chili (CH-19 Sweet) increases
thermogenesis after consumption (Ohnuki et al. 2001).
This can be attributed to an indirect pathway via fat
oxidation, which also generates heat (to the same
pathway as for capsinoids in Figure 1) (Snitker et al.
2009).
Thus, the stimulation of the SNS by chili results in
an increase of noradrenaline hormone, causing the
activation of b-adrenergic receptors found in adipo-
cytes. The sympathetic stimulation of the BAT by lip-
olysis and increased intracellular concentration of fatty
acids increases uncoupled respiration and, therefore,
the up-regulated Uncoupling Protein-1 (UCP-1) in
mitochondria of BAT, resulting in a rise of tempera-
ture as mentioned earlier (see ORANGE colored path-
way in Figure 1). The SNS stimulation is responsible
for the catecholamine secretion from the adrenal
medulla contributing to thermogenesis. Capsaicin and
its non-pungent analog capsinoids as known agonists
for TRPV1 have the potential to increase whole-body
energy expenditure and reduce body fat. When indi-
viduals without active BAT were exposed to cold every
day for 6 weeks, BAT was recruited in association
with increased energy expenditure and decreased body
fat. Importantly, a 6-week daily ingestion of capsinoids
mimicked the effects of repeated cold exposure on
BAT (Yoneshiro & Saito 2013).
Chili reduces appetite
Decreased energy intake is attributed to an increase in
the ratio of sympathetic (SNS) to parasympathetic
(PSNS) nervous system activity (Bray 1993). Elevated
SNS activity most likely may be the reason for the
increased heart rate and systolic blood pressure, as
seen in chili consuming group. There are no reports
in the literature on the parasympathetic nervous sys-
tem activity. Therefore, the increasing effect on the
SNS: PSNS ratio is mainly attributed to the SNS
activation.
Chili increases anorexigenicity (Janssens et al. 2014)
and chili users were not only less hungry but also had
a reduced desire to eat fatty, salty and sweet foods.
This later effect is more prominent in irregular con-
sumers of chili than habitual consumers (Ludy &
Mattes 2011). Chili reduced the desire to eat, tested in
a HF and a HC diet with the effect being more pro-
nounced in the HF diet. Adding chili increased the
sensation of oiliness thereby resulting in satiety
(Yoshioka et al. 1998; Yoshioka et al. 1999). Addition
of chili to breakfast meal decreased the protein uptake
with both diets. When a chili-based appetizer was pro-
vided between breakfast and lunch, ad libitum energy
intake was decreased (Yoshioka et al. 1999; Ludy &
Mattes 2011; Janssens et al. 2014).
The sensation of fullness and increased satiety was
observed in the positive balanced state but not in the
negative balance state (Janssens et al. 2014). These
findings were contradicted by other researchers, who
found a stronger effect on appetite at the negative
energy state (Reinbach et al. 2009). While Smeets and
Westerterp-Plantenga (2009) initially reported no sig-
nificant difference in satiety, they later observed a
INTERNATIONAL JOURNAL OF FOOD SCIENCES AND NUTRITION 5
decrease in appetite when they replaced carbohydrates
by proteins (Smeets et al. 2013).
Supplementing a chili meal with caffeine (Yoshioka
et al. 2001) or green tea (Yoshioka et al. 2001;
Reinbach et al. 2009) reduced energy intake with
respect to control as well as the desire to eat fatty,
salty and hot foods. Chili on its own and with caffeine
results in a significant reduction in energy intake,
which was observed in two independent studies by
Yoshioka et al. (1999,2001). Although there was no
combined study to observe comparisons between
them, both studies separately showed significantly
reduced significant energy intakes. Meanwhile, reduc-
tion in energy intake was more pronounced when chili
was combined with green tea than with chili or green
tea independently (Reinbach et al. 2009).
Chili activates TRPV1, which increases glucagon
like peptide-1 (GLP-1) protein levels via stimulated
SNS and consequently reduces ghrelin (a hunger and
energy state-related hormone) levels in the gut
(Larsen 2008; Smeets & Westerterp-Plantenga 2009).
This causes a decrease in appetite, which leads to
decreased energy intake due to a feeling of satiety.
Overall, the correlation among sensation of fullness,
satiety, or appetite with energy intake is well
established.
Insulin regulation
Insulin is a hormone secreted by the bcells of the
islets of Langerhans and regulates glucose levels in
blood. Insulin resistance (IR) occurs when cells do not
respond to insulin, and glucose is not metabolized,
causing an increased blood glucose level. High-glucose
levels will cause bcells to produce more insulin and if
not metabolized will cause hyperinsulinemia. Insulin
resistance is closely associated with obesity and they
are directly proportional to each other (Kahn et al.
2006).
IR is frequently measured using the Homeostasis
Model Assessment/Insulin Resistance (HOMA/IR)
quotient (which are calculated using fasting glucose
and insulin levels). Improved insulin management
with chili consumption can be attributed to the
increase in GLP-1 production via TRPV1-mediated
calcium increase (BLUE pathway in Figure 1).
Consumption of chili reduces insulin resistance as a
decrease is observed 2-h in the postprandial HOMA/
IR in a chili eating group (Li et al. 2014) and in preg-
nant women (Yuan et al. 2015). Overproduction of
insulin caused by a meal could result in IR. Chili
intake reduces this overproduction and, therefore,
reducing the risk of IR.
Habitual consumption of chili helps in relieving
meal-induced hyperinsulinemia, as lower serum insu-
lin concentrations (Ahuja et al. 2006) and decreased
postprandial insulin levels over time in obese partici-
pants were observed (Kroff et al. 2015). A higher
GLP-1 level triggered by the activation of TRPV1
receptors by capsaicin explains the improved regula-
tion of glucose homeostasis and its tolerance resulting
in lower postprandial insulin levels. This conclusion is
supported by the observation that TRPV1 knockout
mice have a higher insulin resistance (Lee et al. 2015).
Diaz-Garcia et al. (2014) concluded that TRPV1 does
not contribute to glucose-induced insulin secretion in
beta cells as was previously thought, but it is possible
that it may control insulin sensitivity. Another study
showed that capsaicin, independent of insulin,
increases glucose uptake via ROS generation and con-
sequent AMPK and p38 MAPK activations (Kim et al.
2013).
Insulin resistance can lead to diabetes, but diabetes
can also be caused by decreased insulin levels. In the
second case, the supplementation of chili results in
decreased glucose and increased insulin levels. A
decrease in 2-h postprandial plasma glucose (Yuan
et al. 2015) and glucose levels over a period of time
(Kroff et al. 2015) were observed in chili consuming
groups. A study on mice, with two doses of chili add-
ition to meals, showed decreased fasting blood glucose
levels in low chili consuming groups (Islam & Choi
2008). Reduction in plasma glucose and insulin level
maintenance was also observed (Chaiyasit et al. 2009)
with the addition of chili. The reduction observed in
blood glucose levels can also be drawn as a conse-
quence of increased GLP-1 levels with TRPV1 medi-
ated [Ca
2þ
]
i
increase. A more recent study showed
that capsaicin-containing chili supplementation regu-
larly improved postprandial hyperglycemia and hyper-
insulinemia as well as fasting lipid metabolic disorders
in women with gestational diabetes mellitus, and it
decreased the incidence of large-for-gestational-age
newborns (Yuan et al. 2015).
Discussion
Various targets of weight management are affected
with the consumption of chili directly and indirectly
as research indicates. There is a difference with regard
to the effects between regular consumers and non-
users of chili as regular users may be desensitized.
Interestingly, it is hypothesized that this desensitiza-
tion maybe due to reduced SNS activation, which is
also a characteristic of obesity (Ludy & Mattes 2011;
Ludy et al. 2012). Although there are different
6 S. VARGHESE ET AL.
observations (Table 3) in the parameters measured,
these contradictions can be attributed to a number of
factors especially experimental conditions. Some
experiments were conducted on mice and dogs while
most of the studies were on human subjects with vary-
ing populations of different physiological conditions
such as age, gender, ethnicity, pregnancy state, and
physical exercise. Most groups used chili in a meal
whereas some used capsaicin capsules. The type of
chili, the dosage, and the duration of treatment within
each experiment were also different. When chili was
used in a meal, the presence of other bioactive com-
pounds may also be a factor to consider the difference
in readings. For example, differences in the subjects,
like sensitivity to consumption and amount of intake
of chili, etc. all affect resting energy states and metab-
olism and the consumption of chili would only add to
the complexity if the above parameters are not nor-
malized for all the studies so far. If different subjects
are tolerant to different amounts and kinds of chili,
there is a need to set a standard control on each fac-
tor. All these variations may have caused distinguish-
ing trends in some of the parameters discussed above,
such as respiration, temperature, energy intake, and
Insulin regulation.
It is established that athletes have a lower resting
heart rate and the difference between the RQ levels
observed in runners who consumed chili included
meals, can be hypothesized due to the sustained
higher oxygen requirement in athletes.
Reduced body temperature recorded by
Chatsantiprapa et al. (2014), even if statistically insig-
nificant, was similar to the significantly reduced tem-
perature recorded by Ahuja and coworkers (Ahuja
et al. 2006,2007). Although the data were insignificant
in the case of Chatsantiprapa et al., the significant
reduction described by Ahuja and team may be due to
other physiological processes, like anxiety of experi-
menting or other psychological stress that cause
reduction in temperature.
Studies found a decrease in energy intake by
including chili in diet. The results of a single study
that did not show this could be due to the difference
in combination of bioactive compounds affecting the
presence of capsaicin in the system. The presence of
caffeine and bioactive substances in green tea showed
reductions in energy balances but with various
combinations and in different experiments. A com-
bined experiment is required to see the actual
improvement with the combination and if they have a
better effect together than independently. The effects
of chili consumption are similar to the effects induced
by certain other bioactive compounds found in caf-
feine and components of green tea like tea catechins.
The consumption of the combination suggests stron-
ger effects on the parameters measured statistically
and needs further research to clarify significant reduc-
tions in appetite or energy intake.
No observable difference was shown in a study by
Ahuja et al. (2006) of the acute effects of insulin and
blood glucose levels with the consumption of chili,
contradictory to other studies that demonstrated
improved insulin homeostasis with chili. An increase
in insulin level was shown in a high chili dose group
in mice (Islam & Choi 2008). Insulin levels are a deli-
cate balance when both extremes cause an imbalance
in the form of diabetes as hyperinsulinemia. An
increase in the insulin levels would be an advantage in
a diabetic scenario where as detrimental in the latter.
Thus, the predisposed state of the subjects needs to be
considered carefully when consuming chili.
Despite many advantages of chili consumption,
caution is advised on their uncontrolled intake, for
example unfortunate deaths in 2008 and 2013 were
reported when two Caucasian men died after the con-
sumption of an unknown concentration of chili. Such
incidents point to limits on the consumption of chili.
Hypothetically, the deaths may have been caused due
to a disruption in the SEVR or an immediate and pro-
longed tachycardia leading to cardiac arrest.
Further research is necessary to determine the key
dosage and form of intake of chili to better assess its
true potential in weight management. Currently avail-
able data, on non-pungent capsinoids and capsaici-
noinds, can serve as a harbinger in developing a
variant suitable for non-habitual consumers of chili
who are not comfortable with the feeling of hotness
but can still benefit by its use. It is very difficult to
define an ideal dosage as it depends on the circum-
stances and differs from individual to individual. It
can even vary with various parameters such as fre-
quency of consumption, sensitivity to spice, combina-
tions with other bioactive compounds, metabolism,
energy balance, level of fitness, and presence or
Table 3. Studies which report results different from the general observations.
Factors affected Contradictions References
RQ Increased RQ in runners, contrary to other studies Lim et al. (1997)
Temperature Contradictory views on temp Dairam et al. (2008) and Janssens et al. (2014)
Insulin and blood glucose No significant differences Dairam et al. (2008) and Islam and Choi (2008)
INTERNATIONAL JOURNAL OF FOOD SCIENCES AND NUTRITION 7
absence of other health concerns. Furthermore, if the
possibility of chili as a conqueror for obesity is taken
into consideration, the concept of ideal dosage of chili
may extrapolate into the field of personalized medi-
cine. For best results, the ideal dosage hence is crucial,
meanwhile if the consumption of chili causes any
physical discomfort; it is advisable to seek medical
help.
Conclusion
Overall, dietary chili intake can help in regulating fac-
tors that favor weight loss. At this juncture, the ideal
dosage needed to significantly contribute to weight
loss and safe consumption still warrants further
research. But consumption of chili is not a substitu-
tion to regular physical exercise or controlled dietary
plans.
Disclosure statement
The authors report that they have no conflicts of interest.
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