Why some people become, and remain, obese
December 30, 2011
Debra Black
STAFF REPORTER
Why do people become obese? Why can’t they lose weight? And why do those that do lose weight often gain it back? These are questions that have plagued scientists, medical researchers, physicians and the obese themselves.
The key to the answers could come from a recent study that found a brain injury in the area of the hypothalamus which is responsible for controlling body weight, according to Michael Schwartz, a professor of medicine and head of the Diabetes and Obesity Centre of Excellence at the University of Washington.
The study by Schwartz and a team of researchers has found evidence in rats and mice — which were genetically predisposed to be obese — that within 24 hours of being fed a high-fat diet, inflammation begins to occur in the part of the brain that regulates weight.
The study, published in the Journal of Clinical Investigation, also found a high neuro-protective response in certain cells called glia in the hypothalamus which is evidence that there might have been some kind of neuron cell injury in the brain, Schwartz said.
It’s unclear if the high-fat diet itself causes the brain injury which in turn causes the part of the brain that controls weight to malfunction or it’s something else, said Schwartz in an interview with the Star.
But the research provides some insights into what’s going on, he explained. “This is the first evidence of a structural change affecting the brain area responsible for controlling body weight,” he said.
Curious to see if there was any evidence of a similar reaction in humans, Schwartz and his team also looked at MRIs of 34 subjects, who ranged from normal weight to obese.
In the MRIs of the human hypothalamus they found the equivalent of high glia cell activity in obese individuals, suggesting a neuro-protective response triggered by some kind of brain injury. It appears the very same thing is going on in humans.
“This evidence supports the notion that the brain area for weight control — a tiny part of the hypothalamus — becomes damaged in some way. . . . it is likely playing some kind of role and might explain his or her obesity.”
Over the past 15 years many scientific studies have looked at the key circuits used by the brain to maintain normal levels of food intake and body weight as a possible answer to the obesity question.
Many thought a big breakthrough occurred when scientists began understanding that the amount of body fat a person carries with them is biologically defended — a preset amount of fat that the body fights to keep. “This happens in both normal and obese people”, Schwartz said. And that’s what has been the mystery.”
Schwartz began wondering about that and how to explain it. “Many investigators, including ourselves, had come to the conclusion there must be a fixed structural change that occurs in the brain area for body weight control.”
For many who are obese this study may ease some of their pain, Schwartz said.
Too often blame is placed at the feet of those who are obese, suggesting they lack will power and should be able to control their weight.
“Our data says it’s not just will power, but changes to the brain area responsible for body weight control.”
Schwartz and his team are now working on a study that is trying to isolate what might be the cause of the injury in the hypothalamus and the inflammation.
“If you can figure out the cause of the problem, you have a much better chance of developing a treatment,” he said.
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