Eating too much of fatty junk food destroys the brain cells that control weight thereby triggering a vicious circle of obesity, a new study found.
Researchers fed rats what they described as a "typical high-fat American diet" and found they had doubled their calorie intake three days later.
It also showed they had an inflammation in the hypothalamus, the part of the brain containing neurons that control body weight, and though the inflammation stopped a few days later, it recurred after four weeks.
Lead researcher Dr Joshua Thaler, of the Diabetes and Obesity Centre of Excellence at the University of Washington in Seattle, said scientists also detected a healing response to brain injury called gliosis.
"Gliosis is thought to be the brain equivalent of wound healing and is typically seen in conditions of neuronal injury, such as stroke and multiple sclerosis," the Daily Mail quoted him as saying.
'We speculate that the early gliosis that we saw may be a protective response that fails over time. We also detected damage to, and eventual loss of, critical weight-regulating neurons.
"The possibility that brain injury may be a consequence of the over-consumption of a typical American diet offers a new explanation for why sustained weight loss is so difficult for most obese individuals to achieve.
"It is not yet clear whether this presumed neuronal injury is permanent, but it may contribute to weight gain.
"If new medicines can be designed that limit neuron injury during overeating, they may be effective in combating the obesity epidemic," he added.