GLP-1 weight loss injections, widely known as “slimming jabs” or “weight loss pens”, are facing growing scrutiny after new research in the United States suggested the drugs may cause rapid muscle loss alongside fat reduction.
According to a recent report by The Wall Street Journal, the increasingly popular medications — originally developed to treat obesity and Type 2 diabetes — have become a global lifestyle trend due to their dramatic weight-loss effects.
The drugs have reportedly contributed to declining obesity rates in the United States, reduced food consumption and even falling sales of plus-size clothing, with millions experiencing improvements in health and quality of life.
However, researchers warned that some users may unknowingly lose significant amounts of muscle mass while shedding body fat.
An analysis published by the American Diabetes Association found that GLP-1 medications could cause muscle loss of up to 10 per cent in some patients — an effect experts described as comparable to the body ageing more than 10 years in a short period.
Doctors and researchers said the sudden decline in muscle mass could lead to weakness, reduced coordination, instability and lower physical function, particularly among older adults.
Another major concern is that muscle loss may slow down metabolism, increasing the risk of regaining weight once treatment stops.
Experts warned that individuals over the age of 50, patients with osteoporosis and those with limited mobility could face greater health risks from accelerated muscle deterioration, including higher chances of falls and injuries.
Meanwhile, a separate study published in the British Medical Journal (BMJ) found that people using GLP-1 drugs regained weight four times faster than those who lost weight through lifestyle and dietary changes alone.
Researchers also noted that much of the regained weight tended to return as body fat rather than muscle.
Scientists said there is currently limited research and few clear medical guidelines regarding how patients should safely discontinue the medications.
Women may also be more sensitive to the drugs’ side effects, which can include nausea, diarrhoea, migraines and, in rare cases, pancreatitis.
Medical experts are now calling for more extensive clinical trials to better understand the long-term impact of GLP-1 weight loss drugs on muscle health across different groups of patients.
