Weight-loss medications: why weight is regained when treatment stops

Obesity is a growing public health issue worldwide. According to the World Obesity Atlas 2025, if current trends continue, around half of the adult population globally could be overweight or obese by 2030.  

In this context, medications based on GLP-1 agonists have been a major breakthrough in obesity treatment. Drugs such as semaglutide or tirzepatide, sold under brand names like Ozempic, Wegovy or Mounjaro, mimic a natural hormone that regulates appetite, blood sugar and digestion. Thanks to this mechanism, many people achieve significant weight loss. 

In fact, in 2025 the World Health Organization published its first guideline on the use of these medications for treating obesity. But what happens when treatment is stopped? 

How much weight is regained after stopping treatment?  

A significant proportion of the lost weight is regained once obesity medications are discontinued, especially during the first year. Several studies have examined what happens after stopping these treatments. The data show: 

• After one year: A study from the University of Cambridge found that, during the first year after stopping treatment, people regain on average around 60% of the weight they had lost. 
• Later stabilisation: The same study shows that weight regain tends to stabilise and nearly stops once roughly 75% of the initial weight loss has been regained. This means that, in the long term, patients are able to maintain about 25% of the weight they had lost. 
• Rate of regain: A meta-analysis published in The BMJ looked at how quickly weight returns and estimated an average of around 0.4 kg per month after stopping the drug. 

Based on these data, experts estimate that returning to the original weight could take around 18–24 months after stopping treatment.  

However, two important points should be considered: 

• These medications are relatively new. Most studies only have follow-up data for about 12 months after stopping treatment.  
• The response varies between individuals. Some people may regain all the weight lost and even exceed their initial weight. 

Why does the body regain weight so quickly after stopping medication? 

Weight returns quickly because the drug’s effects on appetite disappear, and because obesity is a chronic condition that tends to relapse when treatment is interrupted.  

This regain is driven by a mix of physiological, behavioural and disease-related factors: 

• Return of appetite: GLP-1 receptor agonists (such as semaglutide and liraglutide) reduce appetite and help people feel full sooner. When the medication stops, this effect disappears and hunger returns. Experts describe stopping treatment as “taking your foot off the brake.” 
• Hormonal changes: Providing the body with higher-than-normal levels of GLP-1 over a long period may reduce natural production and make the body less sensitive to the hormone. 
• Lack of new habits: If a person relies solely on the medication to suppress appetite without consolidating dietary, behavioural or environmental changes, weight regain is more likely.  

Obesity is a complex, chronic disease influenced by genetic, biological, environmental and social factors. “There are still many people who think obesity is almost a personal choice,” explains Dr Josep Vidal. Just as with diabetes or high blood pressure, the effects of treatment usually disappear when medication is stopped.  

Is it possible to prevent weight regain with diet and exercise alone? 

Diet and exercise are essential but often not enough to fully prevent weight regain after stopping medication.  

Historically, diet and exercise alone have had limited long-term success in treating obesity. The world around us also makes it harder. Easy access to high-calorie foods and sedentary lifestyles make maintaining weight loss with healthy habits alone challenging.  

For this reason, more and more specialists advocate combining medical treatments with lifestyle changes. 

What role do diet and exercise play? 

Even if they cannot always prevent weight regain, a balanced diet and regular physical activity remain a key part of treatment. Specifically, they can help to: 

• Slow down weight regain: Intensive lifestyle interventions have been shown to reduce the speed of weight regain after stopping medication. 
• Consolidate lasting habits: Learning to control portion sizes and improve nutritional quality is vital to maintaining results after treatment.  

Experts therefore recommend that lifestyle support should always be combined with medication to optimise outcomes.  

Does this mean treatment should be lifelong? 

In many cases, these medications should be considered long-term treatments. This does not mean everyone must take the drug for life, but as with other chronic conditions, the benefits usually disappear when treatment stops. 

A flexible, personalised approach is therefore needed to treat obesity. In clinical practice, options include: 

• Continued treatment: Some patients need to remain on medication to prevent weight regain. 
• Gradual dose reduction: Higher doses are often used during weight loss, with lower doses for maintenance. “We use full doses to reduce weight and then lower, more cost-effective doses to maintain the loss,” explains Dr Josep Vidal. 
• Stopping treatment: In some cases, though less common, people can maintain their desired weight with intensive behavioural and nutritional support. 

Implications for health policy  

This debate also affects how health systems regulate and fund these treatments. In countries such as the UK, organisations like NICE limit prescribing to a maximum of two years.  

Given the high rates of weight regain when treatment stops, some researchers believe these recommendations may need updating to better reflect the chronic nature of obesity. Other challenges include the cost of medication, limited long-term safety data, and inequalities in access between countries. 

INFORMATION DOCUMENTED BY:  

Dr Josep Vidal, Director of the Institute of Digestive and Metabolic Diseases, Hospital Clínic Barcelona