August 2, 2011
There are plenty of theories for why diets don’t work, why the pounds won’t go away or they come back so quickly: Diets make you tired. They eat away at healthy muscle. They’re unnatural and can’t be followed for a lifetime. They may be unhealthy and lacking in vital nutrients. They can lead to eating disorders.
But now a group of researchers from Albert Einstein College of Medicine have a new theory—dieting causes the brain to eat itself. (Their study is published today in Cell Metabolism.)
Scientists have known for a while that when a body becomes starved for sustenance, cells start eating bits and pieces of themselves. It’s a process known as “autophagy” and one that’s a normal part of the cell life cycle; it’s how other cells get energy during the tough times. But it was thought that the brain was largely resistant to autophagy under these conditions.
At least one part of the brain, however, now appears to self-cannibalize. It’s the hypothalamus, which sits right above the brain stem and regulates a variety of functions, including sleep, body temperature, thirst and hunger. The researchers, working with mice, found that neurons in the hypothalamus started eating their own organelles and proteins when the animals were deprived of food. That autophagy then set off a series of steps, which included releasing fatty acids, that resulted in the release of hunger signals, telling the brain that more food was needed.
When the autophagy was blocked by the researchers, though, those hunger signals were blocked. The mice became lighter and leaner after being deprived of food, and they ate less and burned more energy. This insight into metabolism may lead to the development of better treatments for obesity and metabolic syndrome, the scientists write.
In addition, the researchers speculate, the finding may provide clues about why a high-fat diet may make you more hungry—all those fatty acids in the bloodstream may set off that same series of steps that the autophagy of neurons did, making a person more hungry and prompting them to eat even more.
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