Lots of people, including HAES subscribers, believe human beings have a set point or range where their weight will always be. It takes great effort to get your weight above or below your set point, although repeated attempts can probably raise it. If there is a set point, one likely candidate for its controller is the hypothalamus. It comes up enough that it seems worth my time to find out what the hypothalamus is.
The hypothalamus is part of the brain.* It translates the electrical impulses in your brain into signals to endocrine glands to produce and release hormones, which signal the rest of your organs to do their thing. In this way, the brain is like general. It dictates orders to its secretary, the hypothalamus. The secretary than copies all the orders and sends them to the relevant lieutenant generals (glands), who respond by releasing the appropriate hormones. For example, it coordinates the ebb and flow of melatonin (produced by the pineal gland) and cortisol (produced primarily by the adrenal glands), so that you can wake up in the morning and fall asleep at night. It also translates from hormones to the brain, turning “I’m hungry” into cooking, or “I’m horny” into hitting on someone.
What does this have to do with food and weight? If I had a definitive answer to that I would be rich (and better nourished). Damaging specific parts of the hypothalamus while keeping environment constant causes weight change in rats that previously maintained a stable weight. Damaging other parts causes the rat’s weight to be more affected by an environment (i.e. before damage they previously maintained a particular weight regardless of what food was offered. After damage they lost weight when food was unpalatable and gained weight when it was more palatable). And we’ve tracked several hormones that communicate status between the hypothalamus, adipose tissue, and digestive organs, in ways too complicated to fit into this overview post.
In summary, the hypothalamus is the connection point between the brain and your hormones, and no one really knows what either one is saying.
*One thing that always bugs me when I hear the phrase “part of the brain” is “how sharp is the distinction between this part and other parts? Can there be cells where it’s a matter of judgement which section they fall into? Can you just look at an arbitrary brain and say “there, that’s the hypothalamus”?” I eventually found this video, which very explicitly detailed how each part of the brain is separated, except for the hypothalamus, which he just sort of gestured around. As we’ll read later, scientists are able to precisely destroy sub sections of of the hypothalamus so I guess its boundaries are pretty sharp.