For decades, we’ve been told that losing weight is simply a matter of willpower: eating less and moving more. However, modern science has proven otherwise. More on this later. But first, let’s go back hundreds of thousands of years and look at our earliest ancestors. Because they can be blamed for much of the difficulty we have in losing weight today. This is probably the biggest example of “parental fault”.
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For our ancestors, body fat was a matter of survival. Too little means starvation, too much means the body becomes sluggish. Over time, the human body has become very efficient at protecting its energy stores through complex biological defenses directed by the brain. But in a world where food is plentiful and movement is optional, these same systems that once helped us survive now make it difficult to lose weight.
When someone loses weight, the body reacts as if it were a threat to survival. Hunger hormones increase, appetite increases and energy expenditure decreases. These adaptations have evolved to optimize energy storage and use in environments with diverse food access. But today, with the easy availability of cheap, high-calorie, ultra-processed foods, combined with our sedentary lifestyles, the same adaptations that once protected us are now working against us.
As our recent research points out, the brain also has a powerful body weight defense mechanism, in a sense able to “remember” how much that weight used to be. For our ancestors, this meant that even if you lost weight during difficult times, your body could “recover” to normal weight during good times.
But for us modern humans, this means that our brains and bodies remember being overweight, as if our survival depended on it. In fact, when you get heavier, your brain treats that higher weight as a new normal, a level you have no choice but to defend against.
The fact that the body has the ability to “remember” its previous weight helps explain why so many people regain the weight they lost after dieting. Science shows that this weight gain is not a lack of discipline, it’s just your body doing what it evolved to do: protect itself from weight loss.
This is where weight loss drugs like Wegovy and Mounjaro offer new hope. They work by mimicking gut hormones that tell the brain to control appetite.
However, not everyone responds well to these drugs. For some people, side effects make it difficult to continue treatment, and for others, the medication does not seem to lead to weight loss. After treatment is discontinued, the body begins to move again and the weight lost is often regained.
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Advances in obesity and metabolism research mean that in the future, treatments may be able to suppress these signals that cause the body to regain its original weight even after the treatment period has ended.
Research also shows that good health is not the same as a “healthy weight.” In other words, physical exercise, quality sleep, a balanced diet, and mental health can improve your cardiovascular and metabolic health, even if the number on the scale doesn’t materially change.
Whole-of-society approach
Of course, obesity is not just an individual problem. Effectively tackling obesity requires a collective approach. Research suggests that several preventive measures may make a difference, including investing in healthy school meals, reducing junk food advertising to children, designing neighborhoods to prioritize walking and cycling over driving, and standardizing portions served in restaurants.
Scientists also note an early critical stage in life, from conception to about age 7, when a child’s weight regulation system is particularly flexible.
In fact, research shows that factors such as parental nutrition, how the baby is fed, and early life habits can shape how the brain controls appetite and fat storage over the years.
If you want to lose weight, there’s still work to be done. In particular, focus on sustainable habits that support overall health, rather than crash diets. For example, prioritizing sleep can help regulate your appetite. Regular physical activity, such as a simple walk, also improves blood sugar levels and cardiovascular health.
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In other words, obesity is not an individual defect, but rather a biological condition formed by our brains, genes, and the environment in which we live. The good news is that advances in neuroscience and pharmacology are providing new treatment opportunities, while prevention strategies can change the game for future generations.
So if you’re having trouble losing weight and keeping it off, know that you’re not alone and it’s not your fault. The brain is a formidable enemy. But with smarter science, medicine, and policy, we are beginning to change the rules of the game.
* Valdemar Brimnes Ingemann Johansen is a postdoctoral researcher at the Faculty of Health Sciences, University of Copenhagen, Denmark.
* Christopher Clemmensen is an associate professor and group leader at the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen, Denmark.
*This article is republished from The Conversation under a Creative Commons license. Please read the original.
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