When you lose weight on Mounjaro, your body does not exclusively burn fat. Without adequate protein intake, a significant proportion of weight lost can come from lean muscle mass. Prioritising protein is one of the most important dietary adjustments you can make during treatment.
The Science Behind Protein and Weight Loss
Research published in The Lancet and other journals shows that rapid weight loss — common in the early months of tirzepatide treatment — increases the risk of muscle wasting. Muscle is metabolically active tissue; losing it slows your metabolism and can make weight regain more likely once treatment ends. Protein provides the amino acids your muscles need to repair and maintain themselves.
How Much Protein Do You Need?
The British Nutrition Foundation recommends around 0.75g of protein per kilogram of body weight for the general population. However, during active weight loss on Mounjaro, many dietitians suggest increasing this to 1.0–1.2g per kilogram of your current body weight. For someone weighing 90kg, that means aiming for 90–108g of protein daily.
High-Protein UK Foods
You do not need expensive supplements to meet your targets. Affordable, widely available options include:
- Chicken breast — roughly 31g of protein per 100g
- Tinned tuna — around 25g per 100g, and available from most supermarkets for under £1
- Eggs — approximately 6g each; versatile and inexpensive
- Greek yoghurt — about 10g per 100g; choose plain varieties to avoid added sugar
- Red lentils — roughly 9g per 100g (cooked); excellent in soups and dhal
- Cottage cheese — around 11g per 100g
Spreading Protein Across the Day
Your body can only use a certain amount of protein at one time for muscle synthesis — roughly 25–40g per meal. Rather than loading all your protein into dinner, spread it across meals. Add eggs or yoghurt to breakfast, include beans or chicken at lunch, and build dinner around fish or lean meat.
When Appetite Is Low
On higher doses of Mounjaro, eating enough protein can feel challenging. Protein-rich liquids like milk, smoothies blended with Greek yoghurt, or a simple whey protein shake can help when solid food feels unappealing. Bone broth is another gentle option that provides both protein and hydration.
Protecting your muscle mass while losing fat on Mounjaro is crucial for long-term health and maintaining your results. Make protein a priority at every meal.