Writing about nutrition and eating disorders is a bit of a double-edged sword. On one hand, expanding our understanding of how human bodies interact with food can be a powerful tool. This especially applies to people who want to get a better grasp on what exactly is happening in their digestive tracts and bloodstreams. On the other hand, there are people out there (lurking in the shadows of the Internet) who are not only ignorant, but vehemently, hatefully so — about weight, nutrition, and metabolic/obesity science.
A few weeks ago, one such individual left a particularly nasty comment on a story about the relationship between healthy food and satiety. Quoting the comment here would be very un-R29, but suffice it to say that this person displayed a lack of understanding about just why we feel hungry — and why many of us have trouble feeling full.
As many people who struggle with maintaining balance in their food intake can attest, this involves a sensitive, delicate interplay of hormones that can easily get derailed. Essentially, part of why you feel hungry is because of a hormone known as ghrelin, which is produced in the stomach and pancreas. When your digestive and endocrine systems are working properly, ghrelin levels increase leading up to a meal — signaling that your body needs calories — and decrease when you've had enough.
Ghrelin is designed to work together with leptin, a hormone your body releases when you've eaten enough. Under normal conditions, this interplay allows us to eat when we're hungry, and stop when we're full — but, a number of factors can throw things off-balance pretty easily.
So, while many (like the commenter mentioned earlier) assume that eating is a matter of self-control, science shows that the opposite is true. Numerous studies suggest that obese individuals' ghrelin levels don't decrease after eating, meaning there's no crucial signal that the body has had enough to eat. Even worse, some obese patients have been shown to be "leptin-resistant," which makes it that much harder to acknowledge and process feelings of satiety. It's a self-fulfilling cycle; research shows that ghrelin can directly contribute to the accumulation of abdominal fat tissue.
We still have a lot to learn about exactly how these hormones affect things like obesity, weight gain, and eating disorders. And, of course, there are countless other factors at play in how and what we eat, from cultural values to psychology to marketing and advertising campaigns. But, one thing is clear: For many of us, the whole "eat when you're hungry, stop when you're full" thing is way, way easier said than done.