Obesity may impair the brain’s ability to recognize the feeling of fullness after eating fats and sugars, according to a new study.
Furthermore, these brain changes may persist even after clinically obese individuals have lost a significant amount of weight – possibly explaining why many people tend to regain the pounds they lost.
“There is no sign of reversibility – the brains of obese individuals continued to lack the chemical responses that tell the body: ‘OK, you’ve eaten enough,’” said Dr. Caroline Apovian, a professor of medicine at Harvard Medical School and co-director of the Center for Weight Management and Wellness at Brigham and Women’s Hospital in Boston, to CNN.
According to clinical definition, individuals with obesity have a body mass index, or BMI, above 30, while normal weight is a BMI between 18 and 25.
“This study shows why obesity is a disease – there are real changes in the brain,” said Apovian, who did not participate in the study.
The study, published Monday (12) in Nature Metabolism, was a clinical trial in which 30 individuals considered obese and 30 individuals with normal weight were fed sugar, carbohydrates (glucose), fats (lipids), or water (as a control).
The researchers were interested in how fats and glucose would individually trigger various areas of the brain connected to the rewarding aspects of food. They wanted to know if this would be different in obese individuals compared to those with normal weight.
In individuals with normal weight, the study found that brain signals in a region called the striatum decreased when sugars or fats were introduced into the digestive system – evidence that the brain recognized that the body had been fed.
At the same time, dopamine levels increased in those with normal weight, signaling that the brain’s reward centers were also activated.
However, when the same nutrients were given to individuals considered clinically obese, brain activity did not decrease, and dopamine levels did not increase. This occurred when the food was lipids or fats, a sign that the higher the fat content, the more rewarding the food is. That’s why you prefer a burger over broccoli: the fat in the burger will biologically elicit a better response from the brain.
Next, the study asked obese individuals to lose 10% of their body weight in three months – an amount of weight known to improve blood sugar, reset metabolism, and enhance overall health.
The tests were repeated as before – with surprising results. Losing weight did not change how the brain responds to food in obese individuals. The brain was unable to reach fullness or feel satisfied.
You might say that three months is not enough time or that they did not lose enough weight to generate a brain change.
Much more research is needed to fully understand what obesity does to the brain and whether this is triggered by the fat tissue itself, the types of foods consumed, or other environmental and genetic factors.
Source: CNN