Science of weight loss: why your brain is wired to keep you fat
While for decades we have been told how losing weight is just about willpower and eating less and moving more, modern science has proven it isn’t actually the case.
Rather, it’s a battle against biology. While diet plans and workout routines dominate weight loss advice, few people realise that the real struggle often lies within the brain.
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Researchers Valdemar Brimnes Ingemann Johansen, a PhD Fellow in the Faculty of Health and Medical Sciences, University of Copenhagen, together with Christoffer Clemmensen, an Associate Professor and Group Leader at the Novo Nordisk Foundation Centre for Basic Metabolic Research, University of Copenhagen, shed light on the weight loss battle.
While human evolution has hardwired us to hold onto fat as a survival mechanism, making modern weight loss an uphill battle, the duo argues that when someone loses weight, the body reacts as if it were a threat to survival.
“As we found in our recent research, our brains also have powerful mechanisms for defending body weight – and can sort of “remember” what that weight used to be.
For our ancient ancestors, this meant that if weight was lost in hard times, their bodies would be able to “get back” to their usual weight during better times,” they wrote.
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Also adding that for modern humans, it means that our brains and bodies remember any excess weight gain as though our survival and lives depend upon it. So in effect, once the body has been heavier, the brain comes to treat that higher weight as the new normal – a level it feels compelled to defend.
“The fact that our bodies have this capacity to “remember” our previous heavier weight helps to explain why so many people regain weight after dieting. But as the science shows, this weight regain is not due to a lack of discipline; rather, our biology is doing exactly what it evolved to do: defend against weight loss,” they explained.
Hacking biology
The duo further revealed that this is where weight-loss medications such as Wegovy and Mounjaro have offered fresh hope. They work by mimicking gut hormones that tell the brain to curb appetite.
However, the team notes that not everyone responds well to such drugs. For some, the side effects can make it difficult to stick with, and for others, the drugs don’t seem to lead to weight loss at all. It’s also often the case that once treatment stops, biology reasserts itself – and the lost weight returns.
Advances in obesity and metabolism research may mean that it’s possible for future therapies to be able to turn down these signals that drive the body back to its original weight, even beyond the treatment period.
Likewise, the research is also showing that good health isn’t the same thing as “a good weight”. As in, exercise, good sleep, balanced nutrition, and mental wellbeing can all improve heart and metabolic health, even if the number on the scales barely moves.
