Top American scientist shows how brain stops a person from losing weight and how to rewire it

Ever felt stuck in your weight loss journey? After following the same diet and workout regimen, you find it difficult to lose weight as you did earlier? Well, you are not alone. This happens to every person who is trying to lose weight. And the brain is to blame for! Dr. Giles Yeo, a geneticist at the University of Cambridge and an expert on obesity and the brain control of food intake, explains why the weight loss process gets stuck in between. Dr. Yeo, who is the author of ‘Gene Eating: The Story of Human Appetite’ and ‘Why Calories Don't Count: How We Got the Science of Weight Loss Wrong’, details how the brain ‘hates’ to lose weight.

In a video circulating on Instagram, Yeo sheds light on why losing weight is such a formidable challenge for so many. He explains that the human brain is hardwired to resist weight loss, perceiving even minor reductions as a threat to survival. This biological response, rooted in evolutionary survival mechanisms, makes sustainable weight loss a battle against our own physiology.

“Everyone’s brain hates it when they lose weight,” he asserts, noting that this response kicks in regardless of whether someone is athletic or sedentary. When a person sheds even a few pounds, the brain raises a ‘big flag,’ interpreting the loss as a danger to survival. This perception stems from our evolutionary past, where maintaining body fat was critical for enduring periods of food scarcity. In modern times, however, this mechanism often works against those striving to lose weight.

“If your brain is used to you carrying it, you or me carrying a certain amount of weight. The moment your weight starts to go down, this is a big flag that comes up - this is reducing my chance of survival. This is what the brain thinks. So what it does is it begins to use strategies not conscious to drag us back up,” he adds.

According to Yeo, the brain employs two primary strategies to counteract weight loss, First, it triggers hunger, compelling individuals to eat food to restore their previous weight. This is not merely a lack of willpower but a powerful biological signal driven by hormones like ghrelin, which stimulates appetite. Second, and more insidiously, the brain subtly lowers the body’s metabolism. This reduction means that even if a person consumes the same amount of calories as before, their body burns fewer of them, storing the excess as fat.


Though people often frame weight loss as a matter of discipline, Yeo explains that the biological barriers are at play. The brain’s survival-driven strategies explain why many people regain weight after successful diets, a phenomenon known as weight cycling.
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