Why Is Weight Loss Hard For Obese People? Study Explains Reason

Losing weight and maintaining weight loss is always difficult for people with obesity. A recent study explained how the brain responses in overweight people function differently in response to sugar and fat, making weight loss a tough journey.

The findings of the study, published in the journal Nature Metabolism, explained how obesity caused the brain to lose alignment with what was happening in the gut.

"Our interpretation is, there's a generally reduced nutrient-sensing in people with obesity. It could help explain why weight loss and weight-loss maintenance are so hard," senior researcher Dr. Mireille Serlie said.

The study evaluated 30 adults with a healthy body weight and 30 with obesity. The brain responses of the participants to sugar and fat were captured after the nutrients were delivered directly to the gut.

The lean participants showed specific patterns of brain activity when the nutrients were delivered, while these were "severely impaired" in obese people. The participants who were overweight also had a lesser release of dopamine from the striatum of the brain responsible for regulating eating habits.

Even after shedding 10% of their weight on a reduced-calorie diet for three months, the brain responses of the obese participants did not reverse.

Researchers believe that impaired nutrient signaling is not permanent and can be regained with more time and sustained weight loss.

Earlier experiments on lab animals indicated the brain responded to the presence of nutrients in the gut even without the sensory experience of eating.

"The leap forward in this study is that they're showing this is happening in humans, too, but the response is completely blunted in people with obesity," Alexandra DiFeliceantonio, a co-author of the study, said.

The nutrient signaling between the gut and the brain helps people choose what they eat, but the signaling is "broken in some way" due to obesity, DiFeliceantonio added.

Meanwhile, the researchers could not determine when exactly the signaling becomes impaired or how.

According to the study, the secret to lasting weight loss is not always about the "willpower" to continue the diet, as obese people are constantly fighting not only the temptations of cheap, readily available junk food, but also a "hungry brain" that makes diet changes and weight loss difficult.

"I do think people get blamed. This is not about willpower. It's a real struggle. And we're starting to understand why people struggle," Serlie said.

However, through diet, lifestyle changes, and medications the researchers hope to find a way to correct the nutrient signaling in the future.