Thanks to the receptors in the brain, the growth hormones, which are naturally present in the human body, prevent the body from spending too much energy during a dietary restriction.
Why is it so difficult to maintain weight loss after a diet? Researchers at the University of São Paulo in Brazil give an answer: In their study published in Nature Communications, they showed that the growth hormones present in the body hinder weight loss.
A complementary action to leptin
Scientists have long known about the action of the hormone, leptin: when we are hungry, it acts to conserve energy and to block or at least slow down weight loss. The discovery of Brazilian researcher José Donato Junior and his team helps us understand why weight loss treatments that act on leptin levels do not work in the long term. When you diet, another type of hormone reacts: the growth hormones.
The human body naturally contains growth hormones that contribute to skeletal growth and bone growth. Brazilian scientists have discovered that the brain contains receptors for these growth hormones. When we try to lose weight by reducing calorie intake, they send signals to the body to use less energy. The result is the same as with leptin, but the process is slightly different: when we diet, the level of leptin in the blood drops while the level of growth hormones increases.
The action of the hormones is linked to a protein
The growth hormone receptors in the brain act on the AgRP neurons, which are linked to the Agouti protein. When stimulated, they increase the production of this protein, which is able to stimulate hunger and reduce the body’s energy consumption. The body enters a kind of “survival mode”.
In rats, the blocking of these neurons confirms the action of growth hormones. When the growth hormone receptors become inactive, the rats lose more weight and their body consumes more energy. To develop effective slimming treatments, the action of leptin and growth hormone must be combined. The Brazilian study could change the way overweight or obese people are treated and provide an effective long-term solution. In France, one person in two is overweight.