GLP-1 medicines, muscle loss, protein and strength training

When people lose weight by any method, some of the loss is lean mass. Studies of the newer medicines using body-scan techniques show that lean mass is reduced alongside fat, and that the proportion varies by person and by study. Because the total weight lost can be large, the absolute amount of lean tissue lost can be noticeable.

It is important to be honest about uncertainty. Lean mass on a scan includes water and organ weight, and a fall in lean mass does not necessarily mean a proportional loss of functional strength. Researchers are still working out how much of the change is clinically meaningful and whether it differs from diet-induced loss.

Reduced appetite means smaller meals, and protein-rich foods are often the first to feel unappealing. Fewer meals can make it harder to reach protein needs. Some people find meat, eggs or dairy off-putting in the early weeks. Planning matters because it rarely happens by accident.

• Build each meal around a protein source such as fish, eggs, poultry, pulses, tofu, yoghurt or cottage cheese.

• Take the protein part of the meal first, before you feel full.

• Use nourishing snacks, such as yoghurt, milk or a handful of nuts, if meals are very small.

• Ask a dietitian to estimate a target for you if you have kidney disease, because high protein is not appropriate for everyone.

Muscle responds to load. Resistance training, whether with weights, bands or body weight, is the main stimulus for maintaining muscle during weight loss, and national physical activity guidance recommends muscle-strengthening activity on at least two days a week for adults. Starting with supervised sessions can help if you are new to it or have joint problems. A physiotherapist or qualified exercise professional can adjust exercises around pain or arthritis.

Older adults, people with existing sarcopenia, people recovering from illness or surgery and those with a low starting BMI relative to their frame are at greater risk of harm from losing lean tissue. A prescriber should weigh this before starting, and consider whether the goal is better pursued differently. If you notice weakness, trouble rising from a chair, falls or fatigue, tell your clinician.

Ask whether body composition or grip strength will be considered as well as weight, whether the service has dietitian input and how protein will be addressed. Services that only record weight on the scales miss part of the picture.