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London - One of the most frustrating mysteries of weight loss is why the kilos seem to pile back on despite following a successful diet.
Researchers found that being obese can reset “normal” body weight to a permanently elevated level.
Tests in mice found that the longer the animals remained overweight, the more likely their condition would become “irreversible”, making it difficult to maintain weight loss.
Study author Dr Malcolm Low, of the University of Michigan, said: “Our model demonstrates that obesity is in part a self-perpetuating disorder and the results emphasise the importance of early intervention in childhood to prevent the condition whose effects can last a lifetime.
“Our new animal model will be useful in pinpointing the reasons why most adults find it exceedingly difficult to maintain meaningful weight loss from dieting and exercise alone.”
The researchers used a new model of obesity-programmed mice that allowed weight loss success to be tracked at various stages and ages by flipping a genetic switch that controls hunger. Turning on the switch right after weaning prevented the mice from overeating and becoming obese.
Similarly, mice that remained at a healthy weight into young adulthood by strict dieting alone were able to maintain normal weight without dieting after turning on the switch.
However, chronically overfed mice with the earliest onset of obesity never returned to normal weight after flipping the switch, despite marked reduction in food intake and increased activity.
The new findings might raise questions about the long-term success rate of severe calorie restriction and strenuous exercise used later in life to lose weight.
Low said: “Somewhere along the way, if obesity is allowed to continue, the body appears to flip a switch that reprogrammes to a heavier set weight.
“The exact mechanisms that cause this shift are still unknown and require further study that will help us better understand why the regaining of weight seems almost unavoidable.”
The research was a result of collaboration between the University of Michigan and the National Council of Science and Technology of Argentina. – Daily Mail