What the study measured
A 24-week study of 122 adults with overweight or obesity recorded an average weight reduction of 15.8% during treatment with tirzepatide, combined with a low-carbohydrate diet and physical activity guidance. Fat mass fell by about 35%, while fat-free mass dropped by around 5%.
Skeletal muscle mass stayed fairly stable, and metabolic markers improved over the same period, according to the researchers. The results come from routine clinical care rather than a tightly controlled trial.
Why muscle matters
Rapid weight loss can take lean tissue as well as fat, and doctors watch this closely because muscle supports strength, balance and blood sugar control. In this group, the combination of diet changes and activity appears to have limited the loss of muscle.
The authors say support matters. Patients who received clear guidance on protein intake and resistance exercise tended to keep more lean mass, though the study was not designed to prove cause and effect.
Doctors also note that access and cost remain barriers for many patients, and that stopping treatment often leads to weight returning. Researchers say the goal is to pair these medicines with habits that can be kept up for years, so the benefit lasts after a course of treatment ends.
What comes next
The findings add to a growing body of work on how these medicines perform outside trial settings, where patients differ in age, health and routine. Researchers say longer studies are needed to see whether the pattern holds over a year or more.
Doctors stress that these drugs are prescribed alongside lifestyle care, not instead of it, and that side effects and costs should be discussed before starting treatment.
The team also tracked blood pressure, blood sugar and cholesterol, and reported improvements across those measures. They caution that the study had no comparison group, so the results should be read alongside larger randomised trials.