If you have lost weight on a GLP-1 medication like semaglutide or tirzepatide and stopped, you may notice that you slowly gain weight. That is not failure but physiology. 

What happens with GLP-1?

GLP-1 receptor agonists help you eat less by dampening appetite in the brain and slowing gastric emptying, so you feel full on less food. When you stop, those effects wear off, hunger signals are louder, fullness fades faster, and calorie intake increases. Your metabolism doesn’t simply go back to the way it was; it becomes more efficient in storing calories. 

A study reveals that GLP-1 receptor agonists don’t just suppress appetite, they alter food-rewarding pathways in the brain. They reduce cravings for high-calorie foods and make smaller portions feel more satisfying. When the medication is stopped, these neurological changes reverse. 

How does weight regain happen?

After any significant weight loss, whether it be from diet, medications or surgery, your body adapts in ways that nudge weight back up. 

Studies show resting calories burned more than expected for your new size, making regaining easier at the same food intake. 

Leptin drops when ghrelin and other orexigenic (hunger hormones) signals rise and can stay elevated for a year or more after weight loss, driving appetite and craving. When you stop a GLP-1, you lose its counter-signal just as these defences persist. 

Weight loss is mostly fat, but some lean mass is usually lost too. Less lean mass can further lower energy expenditure. GLP-1-based weight loss tends to reduce fat mass substantially with a smaller loss in lean mass, but stopping treatment while appetite rises can reverse these gains. Resistance training and adequate protein help preserve lean mass during and after therapy. 

Studies show that GLP-1 medications affect the gut microbiome, the trillions of bacteria in your digestive system that influence metabolism and weight regulation. When treatment stops, these microbial changes can go back, which can contribute to weight gain through altered nutrient processing and hormone production.

Weight gain can also be due to medication discontinuation. 

To avoid weight regain, stopping medication should be done slowly and gradually. Weaning off the medication should be done slowly the same way as the dose titration. People can stay on the low dose for long time before weaning off completely or the frequency of the medication can be extended, instead of every week, you can take it every 10 days or fortnightly but it is important to talk to your doctor regarding the weaning process and discuss the possible options to minimise the weight regain. 

Kripa, is a Specialist Dietitian at The London Obesity & Endocrine Clinic. She has helped many patients overcome weight management barriers. ©Simplyweight

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