Modern science increasingly rejects the idea that obesity results only from weak willpower or lack of self-control. Researchers now emphasize that excess weight stems from a complex interaction of genetics, hormones, and environment. This evolving understanding challenges long-held assumptions about dieting and personal responsibility.
For years, the phrase “eat less and move more” dominated public discussion. However, nutritionist Bini Suresh, who has worked with people affected by obesity for two decades, says this message oversimplifies reality. She explains that many individuals with obesity show strong determination and deep knowledge about nutrition. Despite consistent efforts, they still struggle to lose weight.
Genetics plays a significant role in this process. Professor Sadaf Farooqi, a genetics specialist at the University of Cambridge, Science explains that certain genes strongly influence body weight. She highlights the MC4R gene as a major factor affecting hunger and fullness signals. Nearly one in five people worldwide carries this gene. When changes occur in such genes, individuals feel intense hunger and rarely experience fullness, even after eating large amounts.
In addition to genetics, the body actively resists weight loss. Dr. Andrew Jenkinson, author of Why We Eat Too Much, explains that every person has a natural “set weight.” When body weight drops below this level, the body reacts defensively. Hunger increases, energy use decreases, and the body works to regain lost weight. This response makes long-term weight loss extremely difficult.
Hormones further complicate the picture. Leptin normally helps the brain recognize stored fat and regulate appetite. However, high insulin levels often reduce leptin’s effectiveness. As a result, the brain fails to register sufficient fat reserves, driving continued hunger.
Environmental changes also play a decisive role. Professor Gijs Fien, author of Calories Are Calories, argues that willpower has not declined over time. Instead, the modern food environment has changed dramatically. Aggressive marketing and widespread access to low-quality food have fueled rising obesity rates. Forty years ago, many people who struggle today might not have faced obesity at all.