How Our Brains Cause Weight Regain

How Our Hunger Hormones and Emotions are Tied

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Why don't people stick to diets? Do we "overeat" for emotional reasons or biological ones? This is a question that is often asked and has been approached in many different ways. On the one hand, usually people are blamed for "going off a diet," saying that they "lack willpower," or are "compulsive eaters." On the other hand, we know that the levels of certain appetite hormones and peptides rise and fall with weight loss and regain.

Are we essentially asking people to go against their biology if they are to maintain a weight loss?

On a third hand, some people are able to lose large amounts of weight and keep it off (more than 5 years is considered "permanent" -- at least up until that point retaining weight loss is very dicey) with diets and exercise (although even after decades of tracking people's weight loss attempts, I didn't personally know any of these people until I started meeting low-carbers). I personally experienced that what I was calling "compulsive eating" vanished after I adopted a low-carb diet. And on yet a fourth hand, I personally was not able to keep losing weight beyond a certain point, unless I was willing to be hungry all the time. 

So what is going on here?

There was an intriguing clue in a 2008 Columbia University study which attempted to look at some of the many possible factors simultaneously, looking at the brain functions of obese people before and after weight loss, and also two of the hormones responsible for appetite (leptin and ghrelin).

They noticed that after weight loss, when they showed people foods, their brains (observed with a "functional MRI scan") reacted much more emotionally to the food than they had before the weight loss when their "rational brain" had exhibited the main response to the food. This makes sense in a certain way: when people are deprived of food they certainly start thinking and feeling about food very differently and intensely.

When people are in this state, it is much more difficult to think rationally about food choices.

So, are these emotional changes related to the appetite hormones?  The researchers found that they were. For example, another change that happened with the weight loss was that the people had a decrease in leptin (a satiety hormone). So the scientists wondered: what would happen if these relatively leptin-deprived people were given an extra shot of leptin? Well, guess what? When the participants were given some extra leptin, their brain responses reverted to the "rational" response to food! So the brain response and hormone levels appear to be intimately linked. So what we call "emotional eating" just may be one of the methods our bodies use to get us to eat more.

What does all this mean for us? Well, for one thing, it actually gives even more credence to low-carb diets, as preliminary evidence shows that, at least for some people, low-carb diets don't impact appetite hormones in as negative a way as simple calorie reduction does. On the other hand, I don't think many of us escape the hormonal effects all together. Since a moderate weight loss (often just 5-10% of body weight) does produce many health benefits, I think we should start there.

Beyond that, I think we have to rejoice if we get more weight loss, but not be heartbroken if we don't. I also think that this is very exciting research, and may point the way to where some future solutions lie.

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