The dreaded “yo-yo” effect is one of the reasons many people get frustrated before starting a diet. It is widely demonstrated that, after certain types of diets – especially those in which entire groups of nutrients are restricted, or are taken in very little quantity – there is a risk of regaining the weight lost in practically the same time it took to lose it. That happens when, once the objective is achieved, we eat again as before, without including the healthy habits learned.
Maintaining, in fact, is much more difficult than losing weight, and that is why many types of diets focus on giving the same importance to the maintenance phase as to the weight loss phase. In fact, most endocrinology specialists recommend that you not diet and, if you do, do it punctually, with a clear objective and in a slow and controlled manner. Instead, his advice is to learn to eat with nutritional education guidelines that allow you to modulate your diet in a healthy way.
But What is the reason for such rapid weight gain after losing weight? This is the answer to a new investigation, from the Max Planck Institute, of Harvard, which has shown in mice that the communication in the brain changes during a diet, since the nerve cells that mediate the feeling of hunger receive stronger signals, so that you eat much more after you finish it, and you get fatter more quickly. In the long term, the new findings could help develop drugs that prevent this amplification and help maintain a reduced body weight after dieting.
“People have mostly focused on the short-term effects of a diet. We wanted to see what changes in the brain in the long term”explains the researcher at the Max Planck Institute for Metabolism Research, who led the study, Henning Fenselau.
To do this, the researchers put the mice on a diet and evaluated which brain circuits changed. Specifically, they examined a group of neurons of the hypothalamus, AgRP neurons, known for control feelings of hunger. They were able to show that the neural pathways that stimulate AgRP neurons sent more signals when the mice were on a diet. This profound change in the brain could be detected long after the diet ended.
“The physical connection of neurotransmitters between these two neurons, in a process called synaptic plasticity, is greatly increased by diet and weight loss, leading to long-lasting excessive hunger,” says co-author Bradford Lowell, from the School of Medicine. from Harvard.
Avoid the yo-yo effect
The researchers were also able to selectively inhibit the neural pathways in the mice that activate the AgRP neurons. The result was a significantly less weight gain after the diet. “This could give us an opportunity to decrease the yo-yo effect,” says Fenselau. “In the long term, our goal is to find therapies for humans that can help maintain body weight loss after dieting. To achieve this, we continue to explore how we could block the mechanisms that mediate the strengthening of neural pathways in humans as well,” says the researcher.
Spain is the third European country with the highest prevalence of overweight and the fourth in childhood obesity in an index covering 33 countries in the European Region of the World Health Organization (WHO), following research conducted by the Childhood Obesity Surveillance Initiative (COSI). In adults, the rate of obesity has doubled in the last 20 years and it is estimated that more than half –53%- are over their weight, which for endocrinologists means the “great epidemic of the 21st century” and responsible for 7% of total health spending.
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