Brown Adipose Tissue
By Thiyagarajan Sivapriya, M.Sc, M. Phil
The looming pandemic of obesity and overweight, driven by ready access to high-calorie food and an increasingly sedentary way of life, poses a severe threat to global public health. The pathological accumulation of excess dysfunctional adipose tissue that characterizes obesity is a major risk factor for many other diseases, including type 2 diabetes, cardiovascular disease, hypertension, stroke, arthritis, and various types of cancer .
The adipose tissue in mammals is composed of at least two functionally different types of fat: white and brown. White adipose tissue is the primary site of energy storage, modulate whole-body metabolism and insulin resistance. Excess accumulation of white adipose tissue causes obesity  .Brown adipose tissue, on the other hand, is important for both basal and inducible energy expenditure in the form of thermogenesis .
Brown adipose tissue (BAT) has been believed to be negligible or absent in adult humans but recent studies have proved the existence of metabolically active BAT in adult humans . BAT in humans is located in fat tissues in the neck, thorax, and abdomen, juxtaposing deep viscera (heart, lungs, kidneys, adrenals, and intestines) and along the great vessels like carotids, aorta, pulmonary, and mesenteric vasculature .
The contribution of BAT to thermogenesis and its inducibility invitro has created a new paradigm in adaptive thermogenesis in humans, defining new therapeutic directions in obesity treatment through BAT enhancing strategies. The concept of managing obesity through the stimulation of thermogenesis is currently a focus of considerable attention by the pharmaceutical, nutraceutical and functional food industries 
There are numerous bio active components in our foodstuff that have an antagonistic activity, expected to activate BAT and functional in preventing obesity. Let’s be acquainted with a few of them:
- Capsinoids, nonpungent capsaicin analogs, present in red pepper increase energy expenditure through the activation of a subtype of the transient receptor potential channels (TRP) and BAT in humans 
- Methylxanthines: The ability of caffeine, the most abundant dietary methyl xanthine to stimulate metabolic rate was demonstrated in humans almost a century ago both in post-absorptive and postprandial states in lean, obese and post-obese subjects
- Resveratrol and quercetin, two quantitatively important grape polyphenols possess such thermogenic properties
- Oleuropein, a phenolic compound in extra virgin olive oil, has been shown to enhance catecholamine secretion and to increase BAT 
- Lemon polyphenols (hesperidin) suppress diet-induced obesity associated with the up-regulation of gene markers of lipid oxidation in white adipose tissue
- Similarly, dietary supplementation with soy isoﬂavones has been shown to decrease fat accumulation in several animal models of obesity 
- Finally, the small polyphenolic ﬂavonol molecule kaempferol (found in broccoli, spinach, berries) increases thermogenesis in human skeletal muscle myoblast 
The usage of herbal preparations, nutraceuticals and functional foods in the management of body weight has generally been perceived by the medical establishment as essentially anecdotal. With research likely to generate many new candidate bioactive components, with the market likely to be overwhelmed with new products containing combinations of these components and with claims of a more effective multi-targeted approach for weight control, the challenge for regulatory agencies is to decide as to what type of safety and efﬁcacy standards these single target or multi-target products should be subjected before being ‘approved’ as supplements or functional foods for the purpose of managing human obesity.
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