Dieters struggle to lose weight because a lack of nutrition forces their brain cells to eat themselves, making the feeling of hunger even stronger, scientists claim.
Like other parts of the body, brain cells begin to eat themselves as a last-ditch source of energy to ward off starvation, a study found.
The body responds by producing fatty acids, which turn up the hunger signal in the brain and increase our impulse to eat.
Researchers from the Albert Einstein College of Medicine at Yeshiva University in New York said the findings could lead to new scientifically proven weight loss treatments.
Tests on mice found that stopping the brain cells from eating themselves – a process known as autophagy – prevented levels of hunger from rising in response to starvation.
The chemical change in their brains caused the mice to become lighter and slimmer after a period of fasting, the researchers reported in the journal Cell Metabolism.
Dr Rajat Singh, who led the study, said: "A pathway that is really important for every cell to turn over components in a kind of housekeeping process is also required to regulate appetite.
"Treatments aimed at the pathway might make you less hungry and burn more fat, a good way to maintain energy balance in a world where calories are cheap and plentiful."