Losing weight is one of the main aims of bariatric surgery, but not every kilogram lost comes from body fat. During significant weight loss, the body can also lose some lean mass, including muscle.
This is particularly relevant after bariatric surgery because food intake reduces considerably and weight can fall relatively quickly, especially during the first few months. Although some loss of lean mass may occur, adequate protein, good nutrition, and appropriate physical activity can help maintain muscle during weight loss.
Why Can You Lose Muscle When Losing Weight?
When you consume fewer calories than your body needs, it uses stored energy. While much of the weight lost comes from body fat, some lean tissue can also be lost.
After a gastric sleeve or gastric bypass, portion sizes are much smaller, and the range and texture of foods are temporarily restricted during recovery. This can make it more challenging to meet protein requirements.
Maintaining muscle is important for strength, movement, and everyday activities, making it an important part of healthy weight loss after bariatric surgery.
Make Protein a Priority After Bariatric Surgery
Protein provides amino acids that the body uses to maintain and repair tissues, including muscle.
Individual protein requirements vary depending on factors such as the type of surgery, body size, health, activity levels, and stage of recovery. Your bariatric team or dietitian can advise you on an appropriate intake.
As you progress through your post-operative diet, suitable protein sources may include eggs, fish, chicken, Greek-style yoghurt, cottage cheese, beans and lentils.
For more practical ideas, you can also explore our high-protein bariatric recipes.
With smaller portions, prioritising the protein part of your meal can help you meet your nutritional needs.
For some patients, protein supplements or protein shakes may sometimes be recommended, particularly during the earlier stages when meeting protein requirements through food alone is difficult. These should be used according to advice from your bariatric team.
Include Strength Exercise When It Is Safe
Walking is often encouraged following bariatric surgery and is a useful way to gradually increase activity during recovery. However, resistance or strength exercise has a more specific role in maintaining muscle.
Once your surgical team confirms that it is safe, this may include bodyweight exercises, resistance bands, or appropriately supervised weight training. Resistance should be introduced gradually according to your recovery and physical ability. You can read more about exercise after bariatric surgery and how to safely build activity into your longer-term recovery.
Research suggests that structured exercise following bariatric surgery, particularly programmes that include resistance training, can help improve muscle strength and physical fitness.
Don’t Try to Speed Up Your Weight Loss
Eating less than recommended in an attempt to lose weight faster can make it more difficult to get enough protein and other essential nutrients.
Weight-loss rates vary between individuals according to factors such as the bariatric procedure, starting weight, body composition, health, and activity levels. Rather than focusing on how quickly the scales are changing, follow your post-operative diet and attend your recommended follow-up appointments.
Can You Regain Muscle After Weight Loss?
Muscle can respond to resistance exercise and appropriate nutrition, although rebuilding muscle after significant weight loss takes time.
Following bariatric surgery, this does not mean substantially increasing calories or beginning an intensive exercise programme. Gradually increasing strength-based activity when medically appropriate, alongside adequate protein and a balanced bariatric diet, can help support muscle strength and function.
If your weight has stabilised and building muscle becomes a specific goal, your bariatric team or dietitian can advise you on how to adjust your nutrition safely.
Don’t Forget Vitamins and Minerals
Good nutrition after bariatric surgery goes beyond protein. Bariatric procedures can increase the risk of nutritional deficiencies, although the risks vary according to the operation.
Taking the vitamin and mineral supplements recommended for your procedure and having regular blood monitoring are important parts of long-term bariatric care. Some deficiencies can develop gradually without obvious symptoms, so continue your recommended supplements even if you feel well.
When Should You Speak to Your Bariatric Team?
The scales alone cannot tell you whether the weight you are losing is fat, muscle, or water.
Speak to your bariatric team if you experience persistent weakness or fatigue, struggle to meet your protein requirements, have difficulty tolerating food or notice that everyday activities are becoming harder rather than easier.
Maintaining muscle after bariatric surgery is not about preventing weight loss. It is about supporting strength and good nutrition while you lose excess weight.
Prioritising protein, gradually introducing resistance exercise, taking your recommended supplements, and keeping up with follow-up care can all help.
At Phoenix Health, nutritional guidance and long-term aftercare are part of your bariatric treatment, helping you adapt to the changes after surgery and work towards healthy, sustainable weight loss.
References
Gualano B, Kirwan JP, Roschel H. Exercise is Key to Sustaining Metabolic Gains After Bariatric Surgery. 2021. https://pmc.ncbi.nlm.nih.gov/articles/PMC8588125/
O’Kane M, Parretti HM, Pinkney J, et al. BOMSS Guidelines on perioperative and postoperative biochemical monitoring and micronutrient replacement for patients undergoing bariatric surgery. 2020. https://doi.org/10.1111/obr.13087
Bellicha A, van Baak MA, Battista F, et al. Effect of exercise training before and after bariatric surgery: A systematic review and meta-analysis. 2021. https://doi.org/10.1111/obr.13296
NHS. How to improve your strength and flexibility. https://www.nhs.uk/live-well/exercise/how-to-improve-strength-flexibility/
Medically Reviewed by Lujain Alhassan, BSc, ANutr
Registered Associate Nutritionist and Bariatric Nutrition
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