Now, I know at first this may seem a little confusing. Have no fear though. I shall explain!
There are two main hormones that are responsible for regulating your appetite, ghrelin and leptin. When you’re hungry or full, your brain gets the message from your body via many nervous and hormonal feedback mechanisms. Thus, when given the right stimulus, ghrelin or leptin is secreted into the blood.
When you’re HUNGRY, your brain signals your stomach to contract. This causes the secretion of ghrelin from specialized cells found in your stomach and pancreas – circulating levels of ghrelin INCREASES appetite.
When you’re FULL, your brain primarily stimulates your fat cells (or adipocytes) to secrete leptin – circulating levels of leptin SUPPRESSES appetite and breaks down stored fat cells.
So, how does being overweight relate to any of this?! Well, when an individual accumulates too many fat cells (or becomes overweight), it causes these cells to secrete something called c-reactive protein. This is VERY significant because as c-reactive protein binds to circulating leptin, it INHIBITS leptin from entering the brain. This further prevents the brain from sensing satiety and thus, encourages us to eat more as we become leptin resistant.
Here’s a visual aid for you:
P.S. I found this really cool video describing this concept in further detail. Enjoy!