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How Your Hormones Affect Your Weight

By Ryan Moon, MD


If you’re like most people, you have a demanding job, a hectic family life and an out-of-control to-do list. No wonder you feel overworked, overcommitted and all-around overwhelmed. And good sleep is a distant memory. These are all the signs of stress. And through a series of chemical reaction in our body, stress can cause a surge in hormones which can activate an increase in your appetite.


Obesity and hunger, once thought to be direct results of a “weak will”, are now being thought of as a result of a complex interaction between hormones, peptides, chemicals, and neural pathways in our body. It is the constant “chatter” of these players that produces hunger and satiety, and it is thought that any disruption of this “intermingling of characters” can lead to hunger, and ultimately, weight gain. So who are these “cast members” in this play on obesity?


Ghrelin is considered by some to be the main “hunger hormone”. This peptide, synthesized by endocrine cells in the lining of the stomach, primarily stimulates appetite, and counteracts leptin.


Leptin, derived from the Greek word for “thin”, arises from fat cells. It mainly functions as a messenger to the hypothalamus in the brain, dampening one’s eating behavior and acting as a “satiety agent” which signals fullness.


Neuropeptide Y is the most abundant peptide in the brain, and is one of the most potent peptides acting on feeding behavior. Ghrelin stimulates the neuropeptide Y neurons in the brain to increase hunger.


Adiponectin is a mixture of peptides primarily secreted by fat cells as well. These peptides assist in the control of the metabolism of sugars and fats, and help to increase insulin sensitivity.


Cholecystokinin, a peptide released in the first portion of the small intestine in response to high-fat meals, helps to signal the brain to produce a sense of fullness.


Peptide YY, yet another gut-chemical, is thought to slow digestion and suppress appetite, thus lowering food consumption.


Some of the more commonly known hormones also play a significant role in our hunger patterns and metabolism. For example, insulin helps to determine if the sugar we consume is utilized right away for immediate energy, or stored as fat. Sleep deprivation can alter the levels of melatonin, a hormone that assists with the circadian rhythm and sleep. The alteration in melatonin levels has been shown to increase ghrelin production, thus stimulating your appetite. Thyroid hormone, stress hormones, and sex steroids (estrogen, progesterone, and testosterone) have also been linked to hunger and satiety, as well as weight regulation.


As you can see, hunger and satiety are not controlled by the mind alone and habitual patterns of mindless eating. Rather, it appears to reflect a complex and integrated mechanism involving multiple organ sites and systems. The more we understand the “cast members” and their roles, the greater chance we have of understanding obesity.