The classic and generally effective recipe for losing weight is summarized in two combined measures: taking care of your diet and increasing physical exercise to tip the calorie balance until it becomes negative. That is the canonical formula, but the arrival of drugs like Ozempic, Wegovy or Mounjaro has turned it upside down. So much so that we are even giving up those basics.
Thus, a paradoxical fact occurs: there are people losing weight (with Ozempic and similar) and exercising less. This indicates the breakdown of a healthy metabolic virtuous circle: losing weight invites us to move more, which in turn promotes weight loss.
Thinner. Less athletes. A study presented at the prestigious annual meeting of the Endocrine Society (ENDO 2026) shows that adults with obesity who lost weight with GLP-1 receptor agonist drugs have significantly reduced their physical activity. That is, after losing weight they exercise less.
More specifically: when analyzing 753 patients with obesity and the data from their respective activity bracelets, it was discovered that daily steps fell from 5,047 to 4,487 (560 fewer steps) and the time of moderate or intense exercise fell from 27.9 to 22.2 minutes per day. Those who reduced their activity the most were men and those people with joint or muscle pain.
Why is it important. Because these Ozempic-type drugs are not limited to reducing body fat, but can also contribute to losing lean muscle mass: a body composition analysis of the STEP 1 trial indicates that weight loss with semaglutide corresponds to a reduction in lean mass of up to 40% of the total weight lost. That is why physical activity is essential to maintain strength and general health. If these people move less, the problem worsens.
From a public health perspective, the need to offer explicit exercise prescription to the millions of people who take these drugs is imperative. As explained by Dr. Sajana Maharjan, lead author of the study: “The findings of our study reinforce the idea that exercise cannot be optional for people taking these medications. Specific interventions that encourage physical activity along with obesity medication are needed.”
Context. GLP-1 receptor agonist drugs act in the brain by reducing the feeling of hunger and, as a consequence, caloric intake. What was not clear until now is its effect on the desire to move. There are previous studies in animals that had already suggested that GLP-1 can reduce locomotor activity by acting on the dopaminergic reward system, for example, in mice, but this work transfers it to humans with real information.
Until now, studies on physical activity in patients treated with Ozempic and similar drugs have used questionnaires that people fill out alone, which opens the door to overestimation of actual exercise. However, for this work they have combined real data from Fitbit with the NIH All of Us program.
In detail. Of the 1,950 patients who started treatment, only 753 had sufficient fitness tracker data for analysis. The sample presented a relevant heterogeneous case mix: 81.9% had musculoskeletal pain, 67.3% had hypertension and 48.1% had type 2 diabetes, which adds an important bias since they are complex patients with reasons to move little, with or without the drug.
560 fewer steps may seem little compared to the WHO’s recommended daily total (friendly reminder: they are not the mythical 10,000 steps), but it is important: if the ideal minimum is around 7,000 – 8,000 steps per day to obtain cardiovascular benefit and these patients are already below that, any extra reduction takes them even further away from the minimum health goals.
Yes, but. The study has some important limitations. To begin with, there is no control group (obese patients who did not take this type of drug), so although this is an important clue, it cannot be said with certainty that the drop in activity is caused by the drug and not another factor. Additionally, the sample is highly skewed toward women (almost 8 out of 10) and toward people who already used Fitbit regularly, which do not represent all patients with obesity.
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Cover | Flickr and Gabin Vallet
