Weight loss injections - Part 2
Friend or Foe?
Last week I broached the topic of weight loss injections. As of January 2025, more than 500,000 people in the UK are taking weight loss drugs, including Wegovy and Mounjaro, and it’s estimated that people could lose approximately 15-20% of their weight in a couple of months. These drugs are clearly very powerful tools when it comes to weight management, but the type of weight that’s being lost is crucial – it is fat loss, muscle loss or a combination of both?
Ideally, weight loss should primarily target fat loss while preserving muscle mass, as muscle is important for metabolism, strength, and overall health, especially in midlife. However, we do know there is a negative effect on muscle mass during the weight loss journey. In a clinical trial of semaglutide, the active ingredient in Ozempic and Wegovy, researchers looked at loss of lean muscle mass in a group of 140 adults. The 68-week study found an average fat loss of 10.5kg (1stone 9lbs/23lbs) and 6.8kg (1stone 1 lb/15lbs) of lean mass or muscle, a significant finding.
A clinical trial involving people with type 2 diabetes showed that those on Mounjaro had more fat-free mass loss, but less fat infiltration of muscles compared to those on insulin. A key study, SURMOUNT-1, looked at Mounjaro use in people with obesity and not diabetes. Results showed a 34% reduction in fat mass and an 11% reduction in lean mass.
There are a number of reasons why this happens:
The medications work partly by reducing appetite and increasing feelings of fullness which lead to a significant decrease in calorie intake. When your body is in a calorie deficit and burning more calories than you consume, it starts looking for energy sources, which includes both muscles and fat stores;
They mimic GLP-1, a hormone that plays a role in regulating blood sugar and appetite. GLP-1 can also influence muscle protein synthesis i.e. how muscle is made in our bodies. While the exact mechanisms are still being investigated, it's possible that these medications may affect the balance of hormones involved in muscle growth and breakdown;
If you rely solely on the medication for weight loss and don't engage in regular exercise, especially strength training, you’re more likely to lose muscle mass. Exercise is crucial for stimulating muscle protein synthesis and preserving muscle during weight loss;
Protein is essential for building and maintaining muscle. If you aren't consuming enough protein during this treatment, you may experience more muscle loss than usual, so protein intake is key for muscle maintenance.
In summary, weight loss injections are a powerful tool when it comes to weight management, however they aren’t a quick fix or magic bullet. You will most likely lose both fat and muscle during the process, but the amount of muscle loss will depend on your ability to prioritise the right amount of protein for you and your exercise regimen.
If you’re thinking about starting on weight loss injections, need advice and support when you’re taking them or need help and direction to lose weight and gain muscle, book a discovery call with me. www.myprivatediet.com I’m here to help.
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Ciao for now, Ex.