A review article published in the journal Foods provides a detailed overview of the therapeutic effectiveness of phytonutrients in obesity.
Background
Obesity is a metabolic disease caused by complex interactions between genetic, environmental, and lifestyle factors. An individual with a body mass index (BMI) above 30 is considered obese. The prevalence of obesity is exponentially increasing worldwide, making it a significant public health concern.
Obesity increases the risk of diabetes, cardiovascular disease, neurological disease, and certain malignancies, including breast, liver, pancreatic, kidney, gallbladder, and colorectal cancers.
Phytonutrients present in traditional diets, including the Mediterranean diet, Nordic diet, African Heritage diet, Asian diet, and DASH, are known to have beneficial effects in treating obesity. However, the bioavailability of these phytonutrients depends on various factors, including intestinal digestion and absorption processes, interactions with other substances, cooking processes, and individual differences.
Review: A Comprehensive Review of Phytonutrients as a Dietary Therapy for Obesity. Image Credit: marilyn barbone / Shutterstock
Impact of phytonutrients on obesity
Dietary interventions containing plant-based bioactive compounds have become a promising therapeutic approach for treating obesity mainly because of avoiding adverse side effects caused by anti-obesity drugs. Many studies have been conducted to investigate the anti-obesity effects of these phytonutrients.
Polyphenols
Polyphenols are the most abundant bioactive phytonutrients found in plants. Mechanistically, polyphenols prevent obesity by inhibiting adipocyte differentiation, regulating lipid metabolism, inhibiting appetite, stimulating energy expenditure, and modulating gut microbiota.
Evidence indicates that (-)-Epigallocatechin gallate (EGCG) derived from green tea extracts reduces lipid accumulation by inhibiting adipocyte differentiation and stimulating the conversion of white adipocytes into brown adipocytes. Curcumin has been found to prevent lipid accumulation by increasing lipolysis, preventing fatty acid synthesis, and increasing mitochondrial fatty acid oxidation.
Muscadine grape and muscadine grape wine contain a large number of polyphenols and polysaccharides, which can effectively reduce body weight and prevent lipid accumulation by increasing antioxidant levels, reducing leptin levels, preventing fatty acid absorption, and inhibiting pro-inflammatory mediators.
In clinical trials, consumption of green tea extract-enriched bread has been found to reduce waist circumference and maintain normal blood pressure.
Phlorizin
Phlorizin is a phytonutrient found in apples. The combination of phlorizin and other strategies has been used to prevent body weight gain and reduce fat accumulation. Mechanistically, phlorizin has been found to suppress enzymes associated with fat production and storage and cholesterol synthesis.
Overconsumption of fatty foods alters gut microbiota composition by reducing beneficial bacterial populations. Evidence indicates that phlorizin helps prevent obesity by maintaining gut microbiota composition and intestinal barrier integrity.
Gallic acid
Gallic acid is a phenolic acid derived from vegetables and fruits. Evidence indicates that gallic acid reduces lipogenesis and fat accumulation by activating adenosine 5′-monophosphate-activated protein kinase/sirtuin 1/peroxisome proliferator-activated receptor γ coactivator-1 (AMPK/SIRT1/PGC-1) pathway. Moreover, gallic acid has been found to reduce the size of adipocytes in obese mice.
However, studies involving obese human participants have shown that gallic acid cannot reduce body weight and food intake mainly because of its low bioavailability in blood.
Resveratrol and Quercetin
A combination of resveratrol and quercetin has been found to be effective in reducing body weight gain, adipocyte size, and adipose tissue weight and improving dyslipidemia. These phytonutrients can significantly reduce high-fat diet-induced obesity and inflammation by activating the AMP-activated protein kinase/sirtuin 1 (AMPKα1/SIRT1) signaling pathway.
The combination of resveratrol and quercetin has also been found to inhibit adipogenesis by reducing gene expression of key adipogenic factors and reducing levels of adipokines, adipsin, and glycolysis-related enzymes.
Alkaloids
Alkaloids are nitrogen-containing compounds that can be divided into many sub-classes depending on their precursors. Alkaloids exert anti-obesity effects by increasing lipolysis and thermogenesis and reducing appetite. Evidence indicates that alkaloids inhibit adipocyte differentiation by downregulating PPAR, SREPB-1c, and CEBP proteins.
Cinchonine, an alkaloid, has been found to reduce adipogenesis by downregulating the WNT and galanin-mediated signaling pathways. Other alkaloids, such as lansiumamide B and mahanimbine, have shown anti-obesity effects by inhibiting adipogenesis, preventing hyperlipidemia and fat accumulation, and reducing inflammation and oxidative stress.
Terpenoids
Terpenoids are the largest secondary metabolites mostly found in essential oils. Carotenoids are tetraterpene pigments with anti-obesity properties. These metabolites are known to interfere with nuclear receptors to suppress adipocyte development. Lycopene is also known to prevent obesity by increasing the browning of white adipose tissue, upregulating the expression of thermogenic genes, and reducing the expression of fibroblast growth factors.
Saponins are triterpene glycosides with emulsifying properties. Panax ginseng, Panax japonicas, and Platycodi radix are the most widely known saponins with proven efficacy in reducing obesity.
Anthocyanins
Anthocyanins are plant-derived color pigments with anti-inflammatory and anti-obesity properties. These compounds exert anti-inflammatory effects by preventing nuclear factor kappa B (NF-κB) activation. Evidence indicates that anthocyanins improve gut dysbiosis, prevent lipid accumulation, reduce weight gain, and control obesity.
Cyanidin 3-glucoside derivatives have been found to reduce obesity-induced inflammation by inhibiting adipocytokine secretion. These derivatives have been found to prevent obesity by stimulating energy expenditure and regulating lipid metabolism.
Phytonutrient-based anti-obesity food supplements
The utility of phytonutrients can be maximized by using their byproducts and waste products. Many phytonutrient-rich parts of plants, such as peels, stems, and leaves, are discarded as waste products. Bioactive compounds present in these waste products can be used to develop healthy food supplements.
Innovative food processing technologies can be implemented to extract these bioactive compounds and incorporate them into regional diets to improve nutritional value.