S-LITE shows exercise plus a GLP-1 beats either alone on body composition

Researchers in Denmark reported results from S-LITE, a randomized trial that pitted supervised exercise, the GLP-1 receptor agonist liraglutide, and the two together against placebo for one year after an initial diet-based weight loss ^[1]. The combination produced the largest drop in weight and roughly double the reduction in body-fat percentage seen with either single strategy ^[1].

The trial, run at Hvidovre Hospital and the University of Copenhagen, enrolled adults ages 18 to 65 with a body-mass index of 32 to 43 who did not have diabetes ^[1]. Everyone first followed an 800-calorie-a-day low-calorie diet for eight weeks. Participants who lost at least 5% of their starting weight were then randomly assigned in equal numbers to one of four one-year strategies: exercise plus placebo, liraglutide 3.0 mg per day plus usual activity, exercise plus liraglutide, or placebo plus usual activity ^[1]. After the diet phase, 195 participants had lost an average of 13.1 kg (about 29 pounds) ^[1].

What the numbers showed

At one year, every active strategy held onto more weight than placebo. Compared with placebo, the exercise group was down an additional 4.1 kg (95% confidence interval, −7.8 to −0.4; P=0.03), the liraglutide group 6.8 kg (95% CI, −10.4 to −3.1; P<0.001), and the combination group 9.5 kg (95% CI, −13.1 to −5.9; P<0.001) ^[1]. The combination beat exercise alone by 5.4 kg (P=0.004), but its 2.7-kg edge over liraglutide alone was not statistically significant (95% CI, −6.3 to 0.8; P=0.13) ^[1].

The body-composition results were sharper. The combination strategy lowered body-fat percentage by 3.9 percentage points, about twice the decrease in the exercise group (difference, −1.7 percentage points; 95% CI, −3.2 to −0.2; P=0.02) and the liraglutide group (difference, −1.9 percentage points; 95% CI, −3.3 to −0.5; P=0.009) ^[1]. Only the combination improved glycated hemoglobin, insulin sensitivity, and cardiorespiratory fitness ^[1]. Lean mass was a prespecified endpoint, but the specific lean-mass figures are not in the abstract text available here ^[1].

On safety, increased heart rate and gallstones (cholelithiasis) were reported more often in the liraglutide-only group than in the combination group ^[1].

The exercise program was built to meet World Health Organization activity guidance — at least 150 minutes a week of moderate-intensity aerobic activity, 75 minutes of vigorous activity, or a mix ^[1]. After a six-week ramp-up, participants were encouraged to attend two supervised group sessions a week (30 minutes of vigorous interval indoor cycling plus 15 minutes of circuit training) and to do two more moderate-to-vigorous sessions on their own, with heart-rate monitors used to verify intensity ^[1]. Liraglutide or matching placebo started at 0.6 mg per day and was raised by 0.6 mg weekly toward 3.0 mg; people who could not tolerate a step stayed at their highest tolerated dose ^[1].

Why it matters for patients

Most GLP-1 trials measure pounds on the scale. S-LITE measured what those pounds were made of, and the combination arm is the only one that moved fat percentage, blood sugar control, insulin sensitivity, and fitness together ^[1]. That distinction matters because a drug-only strategy and a drug-plus-exercise strategy can look similar on total weight — the 2.7-kg gap here was not significant — while differing on body composition and metabolic measures ^[1].

It is also worth noting what this trial is and is not. Liraglutide is an older GLP-1 drug; S-LITE did not test semaglutide (Ozempic, Wegovy, Rybelsus) or tirzepatide (Mounjaro, Zepbound), so the size of the effect with newer medicines is not established by this study ^[1]. The exercise program was supervised, individualized, and free to participants — conditions most people outside a trial do not have ^[1].

What the trial does not answer

The trial ran one year after the diet phase, so what happens after the medication or the supervised program stops was not tested ^[1]. It was powered to detect a 4.0-kg weight difference with about 30 participants per group, meaning smaller differences between active strategies could be missed ^[1]. Novo Nordisk supplied the liraglutide and placebo pens and Cambridge Weight Plan supplied the diet products; the investigators state the funders had no role in running the trial or analyzing the data ^[1].