Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a health risk. A body mass index (BMI) over 25 is considered overweight, and over 30 is obese. The issue has grown to epidemic proportions, with over 4 million people dying each year as a result of being overweight or obese in 2017 according to the global burden of disease.
Rates of overweight and obesity continue to grow in adults and children. From 1975 to 2016, the prevalence of overweight or obese children and adolescents aged 5–19 years increased more than four-fold from 4% to 18% globally.
Obesity is one side of the double burden of malnutrition, and today more people are obese than underweight in every region except sub-Saharan Africa and Asia. Once considered a problem only in high-income countries, overweight and obesity are now dramatically on the rise in low- and middle-income countries, particularly in urban settings. The vast majority of overweight or obese children live in developing countries, where the rate of increase has been more than 30% higher than that of developed countries.
The global incidence of chronic diseases is on the rise, with obesity being identified as a key factor and a persistent issue for many years. Despite the availability of various weight management strategies, obesity continues to pose a significant challenge to public health, necessitating the development of innovative dietary and/or pharmacological interventions. Overweight (with a body mass index (BMI) between 25 and 30 kg/m2) and obesity (BMI exceeding 30 kg/m2) are associated with increased mortality due to comorbid conditions such as cardiovascular diseases, diabetes, and cancer.
TABLE 1 Key facts on obesity
Taken from: https://www.who.int/health-topics/obesity
What causes obesity and overweight?
The fundamental cause of obesity and overweight is an energy imbalance between calories consumed and calories expended. Globally, there has been: an increased intake of energy-dense foods that are high in fat and sugars; and an increase in physical inactivity due to the increasingly sedentary nature of many forms of work, changing modes of transportation and increasing urbanization.
Changes in dietary and physical activity patterns are often the result of environmental and societal changes associated with development and lack of supportive policies in sectors such as health, agriculture, transport, urban planning, environment, food processing, distribution, marketing, and education1.
More than one-third of the world’s population is overweight or obese, defined as abnormal or excessive fat accumulation in the body. Consequently, there is an ongoing effort among researchers to discover new and effective treatments for these health issues.
In recent years, a great number of dietary interventions have been conducted to fight against the obesity epidemic, and diets recommending higher protein intake appear promising in preserving lean mass during weight loss. However, adherence to strict long-term dietary restrictions can be challenging. Therefore, daily supplements may be useful in addition to lifestyle modifications if there is solid evidence of their safety and efficacy.
The role of food supplements in weight loss can be quite varied. Some supplements may help reduce appetite or increase fat burning, while others might make it harder for the body to absorb fat from the foods you eat. However, it’s important to note that most health experts agree that making lifestyle changes—including following a healthy dietary pattern, reducing caloric intake, and engaging in physical activity—is the basis for achieving long-term weight loss. Compliance with conventional weight-management programs is notoriously poor, which indicates a need for safe, effective, and acceptable therapeutic options.
In the following text, we will be bringing insights into some interesting ingredients.
Conjugated linoleic acid (CLA)
Conjugated linoleic acid (CLA) refers to a group of fatty acids similar to linoleic acid, which is characterized by 18 carbon atoms and 2 double bonds separated by two carbon atoms. These fatty acids are polyunsaturated, and some may be classified as trans fatty acids. CLA has been the subject of research for its potential as a fat-burning and health-enhancing agent, attributed to its interaction with a group of molecular signaling receptors known as PPAR. These receptors play roles in processes such as fat metabolism, steroid signalling, inflammation, and the regulation of glucose and lipid metabolism.
Despite this, the results from human studies on CLA have been inconsistent and generally not very strong, with some findings even being contradictory. While CLA serves as a valuable research tool for studying fatty acids and the PPAR system, its effectiveness as a dietary supplement for individual health objectives appears to be limited.
The following study aimed to systematically review controlled clinical trials examining the effects of CLA on anthropometric indices and body composition in overweight and obese subjects. Based on the current systematic review and meta-analysis, supplementation with CLA can significantly but slightly reduce body weight, BMI and FM and increase LBM in overweight and obese subjects. However, its effects on WC were not statistically significant. In conclusion, supplementation with CLA can slightly reduce body weight, BMI and FM and increase LBM in overweight and obese subjects2.
Another study followed the effects of 13 weeks of conjugated linoleic acid (CLA) supplementation in overweight subjects after weight loss on weight regain, body composition, resting metabolic rate, substrate oxidation, and blood plasma parameters.
This study had a double-blind, placebo-controlled randomized design. Subjects were first submitted to a very low-calorie diet (VLCD 2.1 MJ/d) for 3 weeks after which they started with the 13-week intervention period. They either received 1.8 g CLA or placebo per day (low dosage, LD) or 3.6 g CLA or placebo per day (high dosage, HD). Subjects were total of 26 men and 28 women (age 37.8+/-7.7 y; body mass index (BMI) 27.8+/-1.5 kg/m(2)).
Measurements were done before VLCD (t=-3), after VLCD but before CLA or placebo intervention (t=0) and after 13-week CLA or placebo intervention (t=13), body weight, body composition (hydro densitometry and deuterium dilution), resting metabolic rate, substrate oxidation, physical activity, and blood plasma parameters (glucose, insulin, triacylglycerol, free fatty acids, glycerol and beta-hydroxy butyrate).
In conclusion, the regain of fat-free mass was favourably, dose-independently affected by a 13-week consumption of 1.8 or 3.6 g CLA/day and consequently increased the resting metabolic rate. However, it did not result in improved body weight maintenance after weight loss3.
Green coffee extract
Green coffee extract is a concentrated source of dietary chlorogenic acid and is currently being used for fat loss as a supplement. Green coffee extract is a supplement and/or food product that is derived from green coffee beans.
Studies using green coffee extract (GCE) tend to be dosed based on their chlorogenic acid content. Doses of chlorogenic acid (CGA) in those studies are in the 120-300 mg range.
In a study investigating green coffee bean extract’s impact on weight loss, a 12-week trial involving overweight individuals showed promising results. Consuming 500 mg/day of a standardized green coffee bean extract containing seven CGA isomers, notably CGA-7, led to significant reductions in body weight, BMI, body fat percentage, and fat mass compared to a placebo. It also increased lean mass and improved the lean mass to fat mass ratio. Secondary outcomes like waist and hip measurements, waist-to-hip ratio, and blood lipid levels also showed positive changes in the CGA-7 group. The study confirmed the extract’s safety through analysis of biochemical, and haematological parameters, and vital signs.
However, limitations included the short treatment duration, a smaller sample size from a single study site, and the absence of appetite biomarkers. The study recommends further research to explore the long-term benefits of green coffee bean supplementation. Overall, the findings suggest that CGAs from green coffee beans possess anti-obesity properties and are safe for use as a functional food and food supplements ingredient4.
Curcumin, the primary active compound in turmeric (Curcuma longa), possesses anti-inflammatory properties and shows promising evidence in relieving various conditions, such as chronic pain and depression. However, its effectiveness is hindered by poor bioavailability when used alone, prompting its combination with black pepper or lipids. Extracting curcumin and curcuminoids from turmeric yields supplements with significantly higher potency than the natural herb.
While curcuminoids are prevalent in the curcuma genus, particularly in Curcuma longa, they aren’t exclusive to this plant. The curcumin molecule displays a vibrant yellow colour, often utilized as the food colourant E100.
Curcumin supplementation may promote weight loss and ameliorate obesity-related complications through its antioxidative and anti-inflammatory properties.
Inconsistent data are available about the effect of curcumin supplementation on body weight. This systematic review and meta-analysis was done to summarize data from available clinical trials on the effect of curcumin supplementation on body weight, Body Mass Index (BMI), and Waist Circumference (WC).
One review found a significant effect of curcumin supplementation on body weight and BMI, but not on WC. However, the effect of curcumin on WC was significant in studies done on overweight subjects, used ≥1000 mg/d curcumin, and ≥8 weeks of duration5.
An umbrella review and updated meta-analysis of randomized controlled trials (RCTs) was conducted to evaluate the effect of curcumin supplementation on anthropometric indices. Curcumin supplementation significantly reduces anthropometric indices, and bioavailability-enhanced formulas are preferred. Augmenting curcumin supplement with lifestyle modification should be an option for weight reduction6.
Capsaicinoids alone or in combination with other weight-management ingredients have been shown to promote energy production, support healthy body composition, decrease anthropometric variables (circumference, body weight, body fat), help induce thermogenesis and be well tolerated and safe for human ingestion.
Unprotected capsicum extract is difficult to handle in formulations and production, as airborne particles cause irritation of the eyes, skin, and respiratory system and may lead to cross-contamination during the formulating and manufacturing processes. It is important to have encapsulated particles in the extract to protect the stomach lining and skin from a burning sensation and irritation.
Animal studies have shown that capsaicin plays a positive role in weight management. However, the results in human research are controversial.
Following systematic review and meta-analysis aimed to evaluate the effect of capsaicin (Figure 1) on weight loss in adults.
FIGURE 1 The molecular structure of capsaicin isolated from chili peppers8
Taken from: Zheng J, Zheng S, Feng Q, Zhang Q, Xiao X. Dietary capsaicin and its anti-obesity potency: from mechanism to clinical implications. Biosci Rep. 2017;37(3):BSR20170286. Published 2017 May 11. doi:10.1042/BSR20170286
Epidemiological data revealed that the consumption of foods containing capsaicin was associated with a lower prevalence of obesity.
In one double-blind, randomized, placebo-controlled trial, it indicated that treatment of overweight or obese subjects with 6 mg/day capsinoid for 12 weeks was associated with abdominal fat loss measured by dual energy X-ray absorptiometry. Body weight was decreased as 0.9 and 0.5 kg in the capsinoid and placebo groups respectively. Moreover, none of the patients developed any adverse events7.
The potential mechanisms underlying the anti-obesity effects of capsaicin include: (1) increase lipid oxidation and inhibit adipogenesis; (2) activate BAT activity and induce thermogenesis; (3) suppress appetite and increase satiety regulated by neuronal circuits in the hypothalamus; (4) modulate the function of gastrointestinal tract and gut microbiome. The molecular mechanisms of the anti-obesity effects of capsaicin were summarized in Figure 2.
Capsaicin and its role in gastrointestinal tract and gut microbiome
Capsaicin is passively absorbed in the stomach with greater than 80% efficiency and upper portion of the small intestine. Thus, it may activate local TRPV1 channels in gastrointestinal tract to initiate a series of physiological effects. Dietary capsaicin consumption triggered the intestinal mucosal afferent nerves and increased intestinal blood flow. Acute single administration of 640 μmol/l capsaicin into the duodenal lumen in anesthetized rats significantly increases superior mesenteric artery blood flow. In addition, it showed that dietary capsaicin ameliorated abnormal glucose homeostasis and increased GLP-1 levels in the plasma and ileum through the activation of TRPV1-mediated GLP-1 secretion in the intestinal cells and tissues. Recent study demonstrated that anti-obesity effect of capsaicin in mice fed with high-fat diet was associated with an increase in population of the gut bacterium Akkermansia muciniphila. Further studies found that capsaicin directly up-regulated the expression of Muc2 and antimicrobial protein gene Reg3g in the intestine. These data suggested that the anti-obesity effect of capsaicin is associated with a modest modulation of the function in gastrointestinal tract and gut microbiome8.
In summary, capsaicin plays a critical role in humans and has multiple benefits for metabolic health, especially for weight loss in obese individuals. It is well-accepted that the potential application of active compounds isolated from herbs are similar to the practice of traditional Chinese medicine, which has a holistic approach that can target to different organs and tissues in the whole body. More importantly, no adverse effects with capsaicin were observed in most studies. Thus, chilli peppers and capsaicin are safely and easily applicable to our daily life. Considering that chilli peppers have been a vital part of culinary cultures worldwide and have a long history of use for flavouring, it is more feasible to be utilized to treat overweight and obesity, compared with medications or other interventions with certain side effects. Dietary chilli pepper supplementation or food additives, with ideal dosage, may be tentative methods for capsaicin to play its protective roles in metabolic health. With the widespread pandemic of overweight and obesity, the development of more strategies for the treatment of obesity is urgent. Therefore, a better understanding of the role and mechanism of dietary capsaicin consumption and metabolic health can provide critical implications for the early prevention and treatment of obesity8.
Capsaicin also has on-hold claims pending for weight management and thermogenesis indication. (Table 2)
TABLE 2 On-hold EFSA claims for capsaicin
Effects of probiotics and synbiotics on weight loss in subjects with overweight or obesity
The intestinal microbiota is a potential determining factor in the development of obesity. The objective of this systematic review is to collect and learn, based on the latest available evidence, the effect of the use of probiotics and synbiotics in randomized clinical trials on weight loss in people with overweight and obesity. The intake of probiotics or synbiotics could lead to significant weight reductions, either by maintaining habitual lifestyle habits or in combination with energy restriction and/or increased physical activity for an average of 12 weeks. Specific strains belonging to the genus Lactobacillus and Bifidobacterium were the most used and those that showed the best results in reducing body weight. Both probiotics and synbiotics have the potential to help in weight loss in overweight and obese populations.
This systematic review evaluates the effect of probiotic and synbiotic intake on IM in reducing body weight and/or body fat in apparently healthy people with overweight or obesity in randomized clinical trials.
Probiotics and synbiotics were administered mainly through capsules, but also powders and food products, mainly fermented dairy products such as probiotic yoghurts or fermented kinds of milk.
Most of the studies using fermented foods for the intake of probiotics contained lactic acid bacteria (LAB) as starter cultures, coming from the genus Lactobacillus and Bifidobacterium mainly.
On the other hand, we found a great diversity in terms of probiotic species and strains used to treat overweight and/or obesity. Most of the studies reported the probiotic/symbiotic formulations at the strain level, either using multi-strains] or, single- strain in their formulations.
When used as a single-strain, all probiotic interventions showed positive effects in decreasing body weight, BMI, waist circumference, body fat mass or fat percentage. These strains belonged to the genera Lactobacillus (L. rhamnosus CGMCC1.3724 (LPR) L. gasseri BNR17 , L.gasseri SBT2055, L. sakei CJLS03 and L. plantarum Dad-13), Bifidobacterium (B. lactis Bb-12, B. animalis spp. Lactis 420 (B420), B. animalis CECT8145) and Pediococcus (Pediococcus pentosaceus LP28).
The probiotic amount and duration of the intervention studies varied, from a maximum dose of 5×1010 and the minimum dose of 1×106, and from 4 to 36 weeks, respectively. From the analyzed randomized clinical trials, this systematic review indicates that both probiotics and synbiotics, specifically certain strains of Lactobacillus gasseri, L. rhamnosus, L. plantarum, L. curvatus associated with other Lactobacillus species and/or with species from the Bifidobacterium genus, have the potential to aid in weight and fat mass loss in overweight and obese populations. There is still a need, though, for clinical trials, to state more accurate recommendations in terms of strains, doses and intervention times. It is also suggested to carry out studies in homogeneous populations in terms of sex and age. In addition to this, it would be ideal that future trials would be carried out in the absence of weight loss techniques (such as dietary recommendations for weight loss and physical activity programs), to evaluate the specific effect of the strain/s9.
Food supplements can impact body weight in various ways. Some supplements claim to aid in weight loss by boosting metabolism, suppressing appetite, or increasing fat burning. However, the effects of supplements on body weight can be influenced by individual factors such as diet, exercise, metabolism, and overall health.
The conclusion regarding the impact of food supplements on body weight isn’t straightforward. While some supplements might show short-term effects or modest improvements, the long-term efficacy and safety of many weight-related supplements remain uncertain. Additionally, relying solely on supplements for weight management without lifestyle modifications like a balanced diet and regular exercise might not lead to sustainable or significant weight loss.
- Namazi N, Irandoost P, Larijani B, Azadbakht L. The effects of supplementation with conjugated linoleic acid on anthropometric indices and body composition in overweight and obese subjects: A systematic review and meta-analysis. Crit Rev Food Sci Nutr. 2019;59(17):2720-2733. doi:10.1080/10408398.2018.1466107
- Kamphuis MM, Lejeune MP, Saris WH, Westerterp-Plantenga MS. The effect of conjugated linoleic acid supplementation after weight loss on body weight regain, body composition, and resting metabolic rate in overweight subjects. Int J Obes Relat Metab Disord. 2003;27(7):840-847. doi:10.1038/sj.ijo.0802304
- Sudeep H, Shyam Prasad K. Supplementation of green coffee bean extract in healthy overweight subjects increases lean mass/fat mass ratio: A randomized, double-blind clinical study. SAGE Open Medicine. 2021;9. doi:10.1177/20503121211002590
- Mousavi SM, Milajerdi A, Varkaneh HK, Gorjipour MM, Esmaillzadeh A. The effects of curcumin supplementation on body weight, body mass index and waist circumference: a systematic review and dose-response meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2020;60(1):171-180. doi:10.1080/10408398.2018.1517724
- Unhapipatpong C, Polruang N, Shantavasinkul PC, Julanon N, Numthavaj P, Thakkinstian A. The effect of curcumin supplementation on weight loss and anthropometric indices: an umbrella review and updated meta-analyses of randomized controlled trials. Am J Clin Nutr. 2023;117(5):1005-1016. doi:10.1016/j.ajcnut.2023.03.006
- Snitker S, Fujishima Y, Shen H, et al. Effects of novel capsinoid treatment on fatness and energy metabolism in humans: possible pharmacogenetic implications. Am J Clin Nutr. 2009;89(1):45-50. doi:10.3945/ajcn.2008.26561
- Zheng J, Zheng S, Feng Q, Zhang Q, Xiao X. Dietary capsaicin and its anti-obesity potency: from mechanism to clinical implications. Biosci Rep. 2017;37(3):BSR20170286. Published 2017 May 11. doi:10.1042/BSR20170286
- Álvarez-Arraño V, Martín-Peláez S. Effects of Probiotics and Synbiotics on Weight Loss in Subjects with Overweight or Obesity: A Systematic Review. Nutrients. 2021;13(10):3627. Published 2021 Oct 17. doi:10.3390/nu13103627