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Why diets backfire: A year or more after weight loss, the desire to eat grows stronger

Melissa Healy, Los Angeles Times on

Published in Science & Technology News

Losing weight is, for most people, the easy part. The bigger challenge is trying to keep it off for more than a year.

New research helps explain why people in this second stage are so much more prone to failure.

In a nutshell, people who have shed a significant chunk of their weight are hungrier and have a stronger desire to eat for at least a year after transitioning from weight loss to weight-loss maintenance. And even when their hormones send loud satiety signals to the brain after a meal, they still don't feel full.

The new study, published Thursday in the American Journal of Physiology-Endocrinology and Metabolism, falls in line with a growing field of research that explores the body's tenacious and multi-pronged response to weight loss.

In a bid to ensure that lost weight is regained, the human body has been found to reset its thermostat to burn fuel more efficiently, to economize in calorie-burning movements and to rev up the impulse to find and eat food.

Researchers believe these responses evolved to protect humans against wasting away during times of famine. But in societies where calorific foods are never in short supply, these adaptations have worked to the detriment of dieters.

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Moreover, in people who have become obese, there's growing suspicion that these responses become harder to override. In recent years, researchers have found evidence that obesity makes the brain more "deaf" to some of the gut's satiety signals, and more keenly attuned to signals of hunger.

The new research offers some validation for that surmise.

To study the effects of weight loss in 35 severely obese subjects, Norwegian researchers helped them lose close to a tenth of their weight. They provided dietary advice, exercise coaching and psychotherapy during several three-week stays at a wooded retreat in eastern Norway. All the subjects had a body-mass index greater than 42 (a BMI over 30 is considered obese) at the outset of the study.

At one year, when subjects had lost an average of close to 24 pounds, they returned to the retreat to map out maintenance plans.

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