New Satiety Hormone Described

I've often felt that people who have always had problems with weight have something wrong with their appetite control, so after a meal that would make most people feel full, they're still hungry. And if food is available, it's difficult not to eat it when you're hungy.

I gave an example of this in my book The First Year: Type 2 Diabetes. Someone described a time when a coworker brought some pastries into work and offered them to everyone. A thin person said, "Oh my those look good. I wish I were hungry so I could eat one." The overweight man said he was flabbergasted. He was hungry all the time and just assumed everyone else was too.

Now a new satiety hormone that decreases appetite after eating has been described. The interesting thing about this hormone, called lipocalin-2, is that it seems to work in people who are obese but not in those who are normal weight.

In mice, giving lipocalin-2 long term reduces their food intake and prevents weight gain, without leading to the slowdown in metabolism that is often seen when people try to lose weight by eating less. Studies to see if the mouse results could be replicated in humans showed that normal weight subjects showed an increase in lipocalin-2 after eating, and this coincided with how satisfied they felt after eating.

But in people who were obese, lipocalin-2 levels did not increase after a meal and in fact decreased. It's not clear if they became obese because of a defect in producing lipocalin-2, if they had lipocalin resistance, or if they became obese for other reasons and the obesity caused the defect in lipocalin-2 production. But those who lost weight after gastric bypass surgery (and presumably those who lost weight in other ways) had their lipocalin-2 levels restored to the levels seen in normal weight people, suggesting that the obesity came first.

This sounds like a miracle hormone, but we don't yet know a lot about it. The authors say "the hormone can curb appetite with negligible toxicity," but like most hormones, it does have other effects. For example, it sequesters iron and increases inflammation. and it also plays a role in the central nervous system.

This is not the only hormone that affects appetite; the incretin GLP-1 does the same about the same amount. The GLP-1 agonists like  Byetta and Victoza act in part by reducing appetite.

Time will tell if lipocalin-2 drugs, not yet available, have more benefits than drawbacks. You can read a little more about lipocalin here.