A GLP-1 Won't Make You Fit

Opener

GLP-1 drugs make weight come off, and they make it easier to keep it off. That leads a lot of people to a quiet assumption: if the drug is handling the weight, the training is optional.

A 2026 paper in Sports Medicine tested that assumption directly. Simon Birk Kjær Jensen, Matteo Fiorenza and colleagues at the University of Copenhagen, with Signe Sørensen Torekov as senior author, took adults who had just lost weight and followed them for a year on a GLP-1 drug, an exercise program, both, or neither. Then they measured what the scale can't: how fast people could climb stairs, how fit their heart and lungs were, and how strong their legs were.

The drug kept the weight off. It didn't make anyone fitter. Exercise did.

This lecture goes through what the trial did, what it found, and what it means for a member who is training and following a set diet plan.

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1. The trial

This was a secondary analysis of the S-LiTE trial, a randomized, placebo-controlled study run in Copenhagen.

• Who: 193 adults aged 18 to 65 with obesity (body mass index 32 to 43) and no diabetes or serious chronic illness. About two thirds were women; the average age was about 43.
• Weight loss first: everyone started with an 8-week meal-replacement diet. On average they lost about 13 kg, and losing at least 5% of body weight was required to continue.
• Then four groups for 52 weeks:
  • placebo with usual activity,
  • exercise with placebo,
  • liraglutide with usual activity,
  • liraglutide plus exercise.
• The drug: liraglutide, a GLP-1 drug approved for treating obesity, given daily and increased step by step to the full obesity dose. Most people reached or came close to it.
• Diet advice: every group got the same 12 sessions of general weight-maintenance advice based on national dietary guidelines. Nobody was on a set plan with macro ratios.