Why Weight Loss Drugs Don't Work On Their Own Dr. Nick Fuller (480)

Dr. Nick Fuller, who runs Australia’s largest weight management service at the University of Sydney and Royal Prince Alfred Hospital, opens with a blunt observation: the new weight-loss drugs work while you take them, but up to two-thirds of people stop within the first year, and when they do, they regain the weight. The real problem is not that the drugs fail—it is that people take them without changing their lifestyle, and the drugs do not teach the brain new habits.

Why appetite regulation breaks down in the modern environment

Fuller explains that before the 1950s, most people could rely on their body’s natural appetite regulation system. Hormones like ghrelin (produced in the stomach when you haven’t eaten) signal the hypothalamus to seek food, while other hormones like GLP-1 (glucagon-like peptide-1) tell the brain to stop eating. This system worked well in an environment without processed food on every corner. Today, food chemists engineer products—like Doritos, which Fuller names as his own weakness—to trigger the hedonic or reward pathway in the brain. This overrides the homeostatic system, leading to a slow weight creep of about 0.5 to 1 kilogram per year. The result is that people cycle through fad diets, lose weight temporarily, and then regain it because the body fights the loss.

What the drugs actually do—and why people stop taking them