For many people living with obesity, newer weight-loss medicines such as Wegovy and Mounjaro have been transformative. These drugs are often grouped under the label GLP-1 medicines because they mimic hormones released after eating, helping people feel fuller and less hungry. Mounjaro, whose active ingredient is tirzepatide, also acts on another hormone involved in appetite and blood sugar control.At a time when more than 1 billion people worldwide are living with obesity, these medicines are widely viewed as among the biggest advances in obesity treatment. But one important question is becoming harder to avoid: what happens when people stop taking them?Evidence points to an uncomfortable answer. Many people regain a significant amount of the weight they have lost. A recent study found that, after people stopped weight-loss medications, weight and several heart health markers tended to move back towards pre-treatment levels over time. Other studies have found similar patterns after stopping semaglutide and tirzepatide.This makes biological sense. These medicines work partly by reducing appetite and increasing feelings of fullness. People often describe this as a reduction in “food noise”, meaning the intrusive thoughts, cravings or urges around eating that can make it difficult to eat less. When treatment stops, those drug effects fade. Hunger and cravings may return. If someone then consumes more calories than their body uses, weight regain becomes more likely.This raises the possibility of a new kind of weight-loss cycle.For decades, researchers and clinicians have warned about yo-yo dieting, the repeated pattern of losing weight, regaining it and trying again. A pharmaceutical version of that cycle may now be emerging.Someone may start a medication, lose a significant amount of weight, feel healthier, then stop treatment because of cost, side effects, eligibility rules, shortages or personal choice. Over the following months, appetite returns, eating patterns change and weight begins to creep back. Faced with regained weight, they seek another prescription and restart treatment. They lose weight again. Then the cycle repeats.This should not be read as a criticism of the medicines. They can be highly effective and, for many people, clinically valuable. The problem is the gap between public expectations and the reality of obesity management. Many people understandably hope these treatments will offer a permanent solution. But obesity is increasingly recognised as a complex and chronic health condition, influenced by biology, behaviour, environment and inequality. Long-term support for the management of weight is usually needed.