Written by Slawomir (“Swavak”) Gromadzki, MPH

There are at least 7 key hormones which effect metabolism and regulate satiety: leptin, adiponectin, cholecystokinin (CCK), PYY, serotonin, ghrelin, and insulin. Leptin and adiponectin is released by fat cells, PYY and cholecystokinin by intestines, ghrelin by the stomach, insulin by pancreas, and serotonin is found in intestines and central nervous system. Leptin, cholecystokinin, adiponectin, serotonin, and PYY are supposed to reduce your appetite whereas ghrelin and insulin do the opposite. Because leptin and serotonin play the most important role in preventing and treating obesity I will deal with them separately and in detail.

Insulin is released by pancreas whenever you experience emotional stress and when you consume animal products or plant foods rich in sugar and white flour. In such cases insulin increases your appetite because your body ‘thinks’ you’ve just experienced a stressful situation (because your blood sugar level went high quickly), so now it increases your appetite to encourage you to eat again and supply a new amount of energy to cope with that stressful situation.

Ghrelin it released when your stomach is empty and as a result you should get a massive increase in appetite. As soon as your stomach is full it secretes hydrochloric acid. Ghrelin increases before each meal and its level drops after your stomach is filled with food.

PYY (Peptide YY) is secreted by both the small and large intestines. Injecting PYY reduces appetite in both humans and rats. Therefore it has the opposite effect to ghrelin.

Cholecystokinin (CCK) is a hormone produced in duodenum and released by some neurons in the brain while you eat. Fat and protein in the stomach cause the release of cholecystokinin. It helps digestion and reduces appetite during a meal rather than between meals. Increased blood levels of cholecystokinin is found about 15 minutes after a meal has started. CCK improves digestion by slowing down the emptying of food from the stomach and stimulating the production of bile in the liver to help fat digestion in your intestines. Low level of cholecystokinin caused by unhealthy lifestyle also lead to increased appetite and gaining weight.

Adiponectin is another hormone which, like leptin, is secreted by your fat cells, and is involved in fat metabolism and blood sugar control. People with low levels of adiponectin tend to gain weight and have more body fat. New studies have once again shown that the weight loss and fat burning effect is induced by exercise as it also effectively increases adiponectin levels. Apart from promoting fat burning adiponectin also effectively regulates glucose balance in human body, regulates insulin function, and tends to reduce inflammation.

A study by Kriketos conducted in 2010 revealed that regular exercise increases adiponectin levels and insulin sensitivity in humans. But, apart from exercise, you can increase adiponectin levels in your body also through high in fiber and omega-3 plant-based diet. It is estimated that exercise increases adiponectin levels by 20 to 50% whereas regular consumption of foods rich in fiber (unrefined plant foods) and omega-3 (seeds, nuts, especially chia seeds and fax seeds) can increase the amount of adiponectin even by up to 120%! For this reason scientists now encourage everyone to consume fish because they are rich in omega-3. Fish, however, is not the best nor even safe source of omega-3. First of all, because fish is very high in dangerous toxins such as mercury (absorbed from polluted water); and second, because animal-sources of omega-3 (unlike plant sources) tent to produce a lot of deadly free oxygen radicals in human body. In addition, unlike plant foods fish still contains cholesterol and is often fried with oil in a high temperature. For this reason it is much better to consume plant-based foods rich in omega-3 such as nuts and seeds (especially chia seeds and flax seeds). Unfortunately, not too many people know that chia seeds and flax seeds are much better source of omega-3 than fish. In addition to that, unlike fish, seeds and other unrefined plant foods contain a lot of fiber which also increases the level of adiponectin.

Finally, remember that also stress, by elevating cortisol, decreases the amount of adiponectin in your body.

So, as you can see again and again, the only effective way to remove the true cause of obesity and to recover from this condition always leads to the three famous remedies from God’s pharmacy; regular exercise, stress control, and unrefined plant-based diet.



Gary D. Foster, Cathy A. Nonas (2009). Managing Obesity: A Clinical Guide. American Dietetic Association

Morton, G.J., et al. 2006. Central nervous system control of food intake and body weight. Nature. 443:289-295.

Rosenbaum, M., Sy, M., Pavlovich, K., Leibel, R.L., Hirsch, J. 2008. Leptin reverses weight lossinduced changes in regional neural activity responses to visual food stimuli. J. Clin. Invest. 118: 2583-2591.

Inui A, Asakawa A, Bowers CY, et al. (2004). “Ghrelin, appetite, and gastric motility: the emerging role of the stomach as an endocrine organ”. FASEB J. 18 (3): 43956.

Castaneda TR, Tong J, Datta R, Culler M, Tschop MH (2010). “Ghrelin in the regulation of body weight and metabolism”. Front Neuroendocrinol. 31 (1): 4460.

Fink H, Rex A, Voits M, Voigt JP (1998). “Major biological actions of CCKa critical evaluation of research findings”. Exp Brain Res 123 (12): 7783.

Alvarez Bartolomé M, Borque M, Martinez-Sarmiento J (June 2002). “Peptide YY secretion in morbidly obese patients before and after vertical banded gastroplasty”. Obes Surg 12 (3): 3247.

Batterham RL, Cohen MA, Ellis SM, Le Roux CW, Withers DJ, Frost GS, Ghatei MA, Bloom SR (September 2003). “Inhibition of food intake in obese subjects by peptide YY3-36”. The New England Journal of Medicine 349 (10): 9418.

A. D. Kriketos, S. K. Gan, A. M. Poynten, S. M. Furler, D. J. Chisholm, and L. V. Campbell, 2004. Exercise increases adiponectin levels and insulin sensitivity in humans, Diabetes Care, vol. 27, no. 2, pp. 629630.

Shiloah E, Kanety H, Cohen O, Witz S, Buchs A, Pariente C, Rapoport MJ. 2007. Acute psychotic stress is associated with decreased adiponectin serum levels. J Endocrinol Invest. May; 30(5):382-7.