The use of GLP-1 and GIP agonist medications, like Semaglutide (Wegovy or Ozempic) and Tirzepatide (Mounjaro), is becoming increasingly common for supporting weight loss. They work by reducing appetite and stabilising blood sugar, making it easier to eat less and shed weight. While they can be very effective for fat loss, if not managed carefully they can also have unintended effects on your body composition, such as losing muscle or bone along with fat. When your appetite is smaller, it’s also easy to eat too little or miss out on key nutrients, which can lead to deficiencies. By being aware of potential risks and following a few simple diet and exercise strategies, you can protect your health and make sure your weight loss is safe, effective, and sustainable over the long term.
Why nutrition matters when your appetite drops
GLP-1 and GIP agonist medications work by mimicking natural hormones that help control blood sugar, slow the rate at which food is digested, and reduce hunger. For most people, this leads to eating less because you feel full sooner and cravings are reduced. While that’s effective for weight loss, it also means fewer chances throughout the day to get the nutrients your body needs. That’s why food quality becomes even more important. Without careful choices, you may fall short on key nutrients. Some of the most common risks include:
- Protein shortfalls – Protein is key for preserving lean muscle mass. Losing muscle not only reduces strength and metabolism but can also affect long-term health.
- Bone health – Rapid weight loss can sometimes lead to bone loss, especially if calcium and vitamin D intake are low.
- Fibre gaps – Eating less overall can reduce fibre intake, which may lead to constipation, bloating, and slower gut function. Fibre also supports gut health and helps with blood sugar control.
- Micronutrient gaps – Eating less food overall can mean missing out on vitamins, minerals, and other nutrients that support energy, immunity, and overall wellbeing.
Practical nutrition strategies
Even with a reduced appetite, it’s possible to stay nourished with a bit of planning:
- Prioritise protein at each meal: Aim for around 20–30g of protein from foods like eggs, Greek yoghurt, lean meat, fish, tofu, or legumes. This helps protect muscle and keeps you fuller for longer.
- Choose nutrient-dense foods: Every bite counts. Go for foods rich in vitamins and minerals, like leafy greens, colourful vegetables, nuts, seeds, and wholegrains.
- Don’t forget calcium: Include dairy or fortified alternatives, canned salmon with bones, or leafy greens to support bones.
- Focus on fibre: Incorporate vegetables, fruit, legumes, and wholegrains to help prevent constipation and support gut health.
- Consider smaller or liquid meals: When appetite is low, spreading nutrition across several smaller meals, or including smoothies and soups, can make it easier to get enough protein, vitamins, minerals, and fibre without feeling overly full.
- Think “strategic snacks”: A handful of nuts, boiled eggs, or cheese with wholegrain crackers can plug nutrient gaps and maintain energy.
- Stay hydrated: Water helps digestion, supports energy levels, and can reduce constipation and nausea symptoms.
Exercise: your ally for muscle and bone
While the medications help with appetite, exercise is what helps ensure the weight you lose is mostly fat, not muscle or bone. The best combination is:
- Strength training two to three times a week. Resistance exercises like weights, bodyweight workouts, or resistance bands are essential for preserving muscle.
- Weight-bearing activity such as walking, skipping, jogging, or dancing to strengthen bones.
Getting in some aerobic activity for your heart health is also important, which can include some of the activities mentioned above, or something like cycling or swimming.
Even small amounts add up – consistency is more important than intensity when you’re starting out.
Practical movement strategies
- Think “exercise snacks”: short bursts of movement, like 5-10 minutes of brisk walking, squats, or stair climbing, can be just as valuable as longer workouts, especially if your energy is low.
- Prioritise strength: Aim for simple bodyweight or resistance-band exercises a few times a week to help protect muscle while weight is coming off. Squats, push-ups, and seated band rows are all effective options.
- Sneak in steps: Add extra walking into your daily routine – take the stairs, park a little further away, or walk while on calls. These micro-movements add up.
- Anchor to daily habits: Link movement to something you already do, like calf raises while brushing your teeth or a 5-minute walk after meals to aid digestion.
- Make movement social: Walking with a friend, playing with kids, or joining a group class or activity eg. Parkrun can keep exercise enjoyable and sustainable.
Tracking progress with a DEXA Body Composition scan
A DEXA scan can be a very useful tool for monitoring your body composition during your weight loss journey. A regular scale only shows overall weight, and even advanced tools like bioimpedance scales can only estimate body fat percentage using electrical currents, but their accuracy is often limited. In contrast, DEXA body composition scan is considered the gold standard, providing a clear and precise picture of fat mass, lean muscle, and bone mass.
A DEXA scan provides detailed information about the amount and distribution of fat and lean muscle in your body. When clinically indicated and with a referral, a DEXA bone mineral density scan can also measure bone health.
Having a baseline scan at the start, and repeating it at regular intervals, allows you to see whether your weight loss is coming mostly from fat, while you’re hopefully preserving muscle and bone. This information can help guide adjustments to your diet and exercise plan, ensuring your body stays healthy as you lose weight.
The bottom line
Whatever name you know it by whether it be Ozempic, Wegovy or Mounjaro, they all can be effective tools for weight management, but they’re not a substitute for healthy lifestyle habits, and need to be taken in conjunction with a nutritious diet and regular exercise. Focusing on nutrient-dense foods, getting enough protein, calcium, and fibre, and building regular movement into your week will help protect muscle, bones, and overall health while you lose weight.
Think of it this way: the medication helps you eat less, but your food and exercise choices make sure what you do eat truly nourishes your body.
Sources
- Jensen, S. B. K., et al. (2024). Healthy weight loss maintenance with exercise, GLP-1 receptor agonist, or both combined followed by one year without treatment: a post-treatment analysis of a randomised placebo-controlled trial. eClinicalMedicine, 65, 102174.
- Ryan, D. H. (2025). New drugs for the treatment of obesity: do we need approaches to preserve muscle mass? Reviews in Endocrine and Metabolic Disorders, 26(2), 123–134.
- Cuthbertson, D. J., et al. (2023). Changes in lean body mass with glucagon-like peptide-1-based therapies: a narrative review. Diabetes, Obesity and Metabolism, 25(1), 10–20.
- Watson, S. L., et al. (2025). Resistance and impact training during weight loss improves physical function and attenuates musculoskeletal declines in older adults: a randomized controlled trial. Journal of Cachexia, Sarcopenia and Muscle, 16(3), 456–467.
- Cruz-Jentoft, A. J., et al. (2022). Resistance exercise as a treatment for sarcopenia: prescription and delivery. Age and Ageing, 51(2), afac003.
