The World Health Organization describes obesity as one of the biggest health challenges of our time. While obesity is linked to an imbalance between the calories we take in and the calories we burn, experts still debate how this imbalance actually develops. But there is one point they agree on: obesity is not caused by a lack of willpower.
In the UK, this is now widely recognised. The NHS and leading medical bodies describe obesity as a chronic, complex condition rather than a simple matter of eating too much or moving too little.
The global rise in obesity began around the mid-1970s, and it would make no sense to assume that people suddenly decided to become lazy or undisciplined. Something else changed, and it was not human character.
How ultra-processed foods changed everything
Around 40 years ago, the food industry went through a major change. New technology made it possible to create ultra-processed foods, products designed to be extremely appealing, high in calories and easy to overeat.
Unlike traditional food processing such as cooking, salting, fermentation and pasteurisation, ultra-processing creates combinations rarely found in nature, especially foods high in both fat and carbohydrates. This combination strongly stimulates the brain’s natural reward pathways.
These foods are also designed for the perfect texture, stronger flavour, faster stomach emptying and only brief fullness. This encourages you to eat more calories than your body needs. For people with certain genetic traits, this can lead to intense cravings and overeating that feels impossible to control through willpower alone.
The human body has not caught up with the modern world
For most of human history, survival depended on getting enough calories, not avoiding them. Our bodies evolved to protect us from famine, not from abundance.
Only in the last hundred years or so has food become constantly available, far too short a time for meaningful biological adaptation. This kind of change takes tens of thousands of years, which means our modern environment overwhelms a body still built for scarcity.
Why some people gain weight and others do not
Not everyone exposed to ultra-processed foods becomes overweight, just as not everyone who tries alcohol or nicotine becomes dependent on it.
Genetics play a powerful role in how susceptible you are. People who are genetically predisposed to obesity do not gain weight because they store fat more easily. They gain weight because their genes influence how much they eat, how strongly they respond to food cues and how vulnerable they are to overeating.
The truth: you did not cause this
We still do not fully understand every mechanism behind obesity, but we do know this: obesity is a complex, chronic disease, not a moral failure.
It is shaped by genetics, biology, hormones, psychology and the modern food environment. Blaming yourself only makes the journey harder. You deserve compassion, evidence-based treatment and a fresh start, not guilt.
