A new study from the University of Michigan and the National Council of Science and Technology (Argentina) sheds light on one of the most frustrating mysteries of weight loss - why the weight inevitably comes back. Working with animals, the researchers showed that the longer mice remained overweight, the more "irreversible" obesity became. The surprising findings appear in the Journal of Clinical Investigation.
Study author Malcolm J. Low said that over time, the static, obese state of the mice reset the "normal," body weight point to become permanently elevated, despite dieting that initially worked to shed pounds. "Our model demonstrates that obesity is in part a self-perpetuating disorder and the results further emphasize the importance of early intervention in childhood to try to prevent the condition whose effects can last a lifetime," says Low, a professor of molecular and integrative physiology and internal medicine.
Low believes that one of the major strengths of the research was a new model of obesity-programmed mice that allowed weight loss success to be tracked at different stages and ages by flipping a genetic switch that controls hunger.
Turning on the switch right after weaning prevented the mice from overeating and ever becoming obese, he explained. 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 completely returned to normal weight after flipping the switch, despite marked reduction in food intake and increased activity.
The new findings may raise questions about the long-term success rate of severe calorie restriction and strenuous exercise used later in life to lose weight. "Somewhere along the way, if obesity is allowed to continue, the body appears to flip a switch that re-programs to a heavier set weight," Low says. "The exact mechanisms that cause this shift are still unknown and require much further study."
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Source: University of Michigan