FOR DECADES, OUR response to obesity has been remarkably simple.

Eat less. Move more. Try harder.

It’s advice that sounds logical and sensible. It is also overly simplistic and one of the reasons so many people living with obesity blame themselves when it doesn’t work long term.

Today, science tells a very different story. Obesity is not due to a lack of willpower or simply the consequence of poor choices. It is a complex, chronic medical condition involving the brain, hormones, genetics and metabolism, further shaped by the modern environment and our lived experiences.

Obesity develops through changes in the biological systems that regulate appetite and body weight within the subconscious brain. We don’t expect someone to decide not to feel thirsty. Hunger is similarly generated by biological systems outside conscious control. We still choose whether and what to drink, but we don’t choose whether we feel thirsty in the first place.

Like asthma or high blood pressure, it has biological and environmental drivers, health consequences and evidence-based treatments.

Understanding that doesn’t reduce the importance of good health behaviours, nutrition or physical activity. But it helps us understand why those measures alone may not be enough for many people.

It also helps explain why a new generation of obesity medications has generated so much attention.

Your body is designed to stop you losing weight

Most of us assume that body weight is largely under conscious control. If we simply wanted it enough, we could eat less indefinitely.

Our biology disagrees.

Humans evolved during a time when food was scarce. Our biology prioritises survival, not fitting into modern clothing sizes or sociocultural ideals. Deep within the brain, specialised regions constantly monitor our energy stores and regulate hunger, fullness, food reward and energy expenditure. Like the thermostat in our home maintains temperature, this complex system works continuously to defend body weight.

When we lose weight, the brain interprets it as a potential threat to survival. Hunger hormones rise. Signals that normally tell us we are full become weaker. Food becomes more rewarding. Cravings increase. The body burns fewer calories than expected, making it progressively harder to maintain weight loss.

These changes are not imagined. They have been measured repeatedly in scientific studies and persist long after weight has been lost and regained. For many people, they result in repeated cycles of losing weight and regaining it despite continued effort. It is biology, not a lack of determination.

Why some people struggle more than others

Research tells us that genetics account for a substantial proportion of a person’s susceptibility to obesity. Some people inherit a more powerful drive or biological systems that defend a higher body weight.

Many other factors, such as sleep deprivation, chronic stress, certain medications, mental health conditions, pain, socioeconomic circumstances and our modern food environment, all interact with our biology to alter our risk.

We now live in a world where highly processed, calorie-dense food is cheap, heavily marketed and available almost everywhere. For someone whose biology is predisposed to obesity, that environment becomes especially difficult to navigate. 

None of this means personal choices don’t matter. They absolutely do. But choices are made within a biological system that is not the same for everyone.

Simply understanding the biology of obesity will not treat it. But it can replace shame with understanding – and that is often where effective treatment........

© TheJournal