Protecting Muscle and Nutritional Health While Using GLP-1 and SGLT2 Medicines

Medicines such as GLP-1 receptor agonists and SGLT2 inhibitors can play an important role in the management of type 2 diabetes, cardiovascular and kidney disease, overweight and obesity.

However, when appetite and food intake fall significantly, the smaller amount of food eaten still needs to provide adequate protein, vitamins, minerals, fibre and energy.

A carefully planned eating pattern can help:

• Preserve muscle strength and physical function.
• Reduce the risk of inadequate nutrient intake.
• Support bone, gastrointestinal and metabolic health.
• Manage medication-related gastrointestinal symptoms.
• Establish sustainable eating behaviours for the future.
• Prepare for changes in appetite if medication is reduced or discontinued.

GLP-1 and SGLT2 medicines work differently

GLP-1 receptor agonists include medicines such as semaglutide, liraglutide and dulaglutide. Tirzepatide acts on both GIP and GLP-1 receptors but has many similar nutritional considerations.

These medicines may reduce hunger, increase fullness, alter food preferences and slow the movement of food through the stomach. Some people find that they can eat only small portions, particularly when starting treatment or increasing the dose.

SGLT2 inhibitors, including empagliflozin and dapagliflozin, work differently. They lower blood glucose by increasing the amount of glucose excreted through the urine. This contributes to some energy and fluid loss and may result in modest weight reduction.

Weight loss can include muscle as well as body fat

When body weight falls, not all of the weight lost is necessarily body fat. Some loss of lean tissue commonly occurs during weight reduction, whether weight loss is achieved through medication, dietary changes or surgery.

The aim is therefore to improve the quality of weight loss: maximising the reduction in excess body fat while protecting muscle strength, mobility, metabolic health and independence.

People who may be particularly vulnerable to muscle loss include:

• Older adults.
• People who begin treatment with low muscle mass or strength.
• People losing weight very rapidly.
• People eating very little protein or total energy.
• People who are physically inactive.
• People experiencing repeated nausea, vomiting or poor intake.
• People with chronic illness, frailty or a history of restrictive dieting.

Protein is important, but protein alone is not enough

Protein provides the amino acids needed to maintain and repair muscle. When appetite is reduced, protein-containing foods can easily be displaced because a person may feel full after eating only a small amount.

Including a protein source at each meal or snack can make it easier to meet individual requirements. Examples include:

• Fish and seafood.
• Eggs.
• Chicken and lean meat.
• Milk, yoghurt and cheese.
• Tofu, tempeh and soy products.
• Legumes, lentils and chickpeas.
• Nuts and seeds.
• A nutritionally complete supplement when clinically appropriate.

Protein intake should be individualised according to age, body size, kidney and liver function, medical conditions, dietary pattern, activity and the rate of weight loss.

Protein should also be combined with regular resistance or strength-based activity. This may include supervised gym exercises, resistance bands, body-weight exercises, Pilates or appropriately prescribed rehabilitation exercises.

Smaller meals still need to be nutritionally complete

A person may be eating much less food while using a GLP-1 medicine but still require similar amounts of many vitamins and minerals. The nutritional quality of each meal therefore becomes increasingly important.

A balanced meal will generally include:

1. A protein-rich food.
2. Vegetables, salad or fruit.
3. A nourishing carbohydrate such as wholegrain bread, oats, rice, potato, legumes or wholegrain crackers.
4. A small amount of healthy fat such as olive oil, avocado, nuts or seeds.

Which nutrient deficiencies are possible?

GLP-1 and SGLT2 medicines do not automatically cause vitamin and mineral deficiencies. The concern is more often indirect: reduced appetite, gastrointestinal symptoms, food aversions or restrictive dieting may result in an inadequate or poorly varied diet.

Nutrients that may require attention include:

• Iron.
• Vitamin B12 and folate.
• Thiamine and other B-group vitamins.
• Calcium and vitamin D.
• Zinc and magnesium.
• Essential fatty acids.
• Fibre.
• Protein.

Fibre and fluid remain important

Constipation can occur when people eat less food, drink less fluid or reduce their intake of fruit, vegetables, wholegrains and legumes.

Fibre should usually be increased gradually and accompanied by adequate fluid. Useful foods may include oats, kiwi fruit, pears, prunes, legumes, chia seeds, vegetables and wholegrain cereals.

An important warning about SGLT2 inhibitors

Anyone taking an SGLT2 inhibitor should discuss fasting, ketogenic diets and sick-day medication management with their doctor or diabetes team.

Use the period of reduced appetite to build long-term skills

GLP-1 medicines can create a period in which hunger, food noise and cravings are less intense. This may provide a valuable opportunity to establish eating behaviours that are harder to develop when appetite is constantly strong.

Helpful long-term skills may include:

• Planning regular and balanced meals.
• Recognising physical hunger, comfortable fullness and emotional eating triggers.
• Eating slowly and without unnecessary distraction.
• Preparing convenient protein-rich meals and snacks.
• Increasing vegetables, legumes and wholegrains.
• Developing non-food strategies for stress, boredom and emotional distress.
• Maintaining strength training and regular movement.
• Protecting sleep and maintaining consistent routines.

What happens when appetite returns?

For many people, appetite increases when a GLP-1 medicine is reduced or discontinued. Hunger, food preoccupation and the amount required to feel satisfied may return.

Weight regain should not be treated as a moral failure or a lack of willpower. Biological appetite regulation is powerful, and obesity and weight regulation often require long-term management.

Preparing for a change in appetite should begin while the medicine is still working well. A longer-term plan may include:

• Continuing regular meals instead of waiting until extremely hungry.
• Maintaining protein, fibre and food volume at meals.
• Monitoring changes in hunger, strength and eating behaviour.
• Planning for higher-risk situations and emotional eating triggers.
• Maintaining resistance exercise and daily activity.
• Arranging medical and dietetic follow-up before medication changes.
• Seeking early support if weight regain begins to increase.

A dietitian can help protect the quality of weight loss

Dietetic care during GLP-1 or SGLT2 treatment should extend beyond providing a calorie target. A dietitian can assess protein and energy intake, meal balance, gastrointestinal symptoms, hydration, fibre, nutritional deficiencies, muscle strength and sustainable eating behaviours.

The most successful outcome is not simply a lower number on the scales. It is improved health achieved while preserving strength, nutritional adequacy, confidence with food and a sustainable way of eating.

References

1. Mozaffarian D, Agarwal M, Aggarwal M, et al. Nutritional priorities to support GLP-1 therapy for obesity. American Journal of Clinical Nutrition. 2025.
2. Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine. 2021;384:989–1002.
3. Pan R, Zhang Y, Wang R, et al. Effect of SGLT-2 inhibitors on body composition in patients with type 2 diabetes mellitus. PLOS ONE. 2022;17(12):e0279889.
4. McCrimmon RJ, Catarig AM, Frias JP, et al. Effects of semaglutide versus canagliflozin on body composition in type 2 diabetes. Diabetologia. 2020;63:473–485.
5. Wilding JPH, Batterham RL, Davies M, et al. Weight regain after withdrawal of semaglutide. Diabetes, Obesity and Metabolism. 2022;24:1553–1564.
6. Aronne LJ, Sattar N, Horn DB, et al. Continued treatment with tirzepatide for maintenance of weight reduction. JAMA. 2024;331(1):38–48.
7. Therapeutic Goods Administration. SGLT2 inhibitors, diabetic ketoacidosis and surgical procedures. Australian Government Department of Health and Aged Care.