How to Preserve Muscle During Weight Loss: Protein and Training
How to Preserve Muscle During Weight Loss: Protein and Training
EFWA KNOWLEDGE HUB · NUTRITION & WEIGHT MANAGEMENT
By Dr Mert Eray Onen, Founder & Academic Director, EFWA · ORCID 0000-0001-8510-7293
Estimated reading time: 6 minutes
Direct answer: preserving lean mass during intentional weight loss usually requires more than chasing a lower scale reading. The best-supported foundation is a manageable energy deficit, sufficient dietary protein, regular resistance training and monitoring that includes strength and function—not body weight alone. Protein supplements can be convenient, but they are not compulsory and they cannot replace an appropriate training stimulus.
Weight loss describes a change in total body mass. It does not tell us how much of that change came from fat, water or fat-free tissues. For instructors and personal trainers, this distinction matters: an apparently successful plan may still be poorly designed if performance, recovery and lean tissue decline unnecessarily.
Why lean mass can fall during weight loss
An energy deficit reduces the energy available to maintain all body tissues. Some loss of fat-free mass commonly accompanies diet-induced weight loss, although the proportion varies with the size and duration of the deficit, starting body composition, age, protein intake, exercise and the method used to measure body composition.
Established evidence: an overview of 12 systematic reviews found that exercise supports favourable body-composition change in adults with overweight or obesity, and resistance training reduced lean-mass loss during dietary weight loss in the evidence available at the time (Bellicha et al., 2021). A more recent systematic review and meta-analysis also concluded that adding resistance exercise to dietary weight loss protects fat-free mass and improves strength, even when the scale does not fall faster (Binmahfoz et al., 2025).
This is an important coaching correction: resistance training is not valuable only because it “burns calories”. Its more distinctive role is to provide a reason for the body to retain force-producing tissue while body mass is being reduced.
What dietary protein contributes
Protein supplies amino acids needed for the continual turnover of body proteins. During resistance training, adequate protein supports the remodelling response to exercise. During an energy deficit, needs may be influenced by the severity of restriction, training load, age, body composition and food quality.
A 2024 meta-analysis of 47 trials in adults with overweight or obesity reported better preservation of muscle mass with higher protein intake during weight loss. In subgroup analysis, intakes above 1.3 g/kg/day were associated with better muscle-mass outcomes, whereas intakes below 1.0 g/kg/day were associated with greater risk of decline (Kokura et al., 2024). This is useful evidence, but it is not a universal prescription. Risk of bias ranged from low to high, strength and physical function did not show the same clear benefit, and grams per kilogram can become impractical when based on a high total body mass.
For context, the European Food Safety Authority population reference intake for healthy adults is 0.83 g/kg/day (EFSA NDA Panel, 2012). That value is designed to cover the needs of the general healthy population; it is not a sport-performance target and does not settle the optimum intake for every person dieting and resistance training. In healthy adults performing resistance exercise, larger meta-analyses suggest that increasing protein can add a small benefit for lean mass, with the response tending to level off rather than rise indefinitely (Nunes et al., 2022).
The EFWA four-part muscle-retention check
The following is an EFWA educational decision aid, not an international clinical guideline. It helps a fitness professional organise observations without drifting into dietetic diagnosis or prescribing.
1. Stimulus: make resistance training genuinely progressive
Include repeated work for the major movement patterns and muscle groups. Record load, repetitions, sets, range and effort. Progress one variable when the current dose is performed reliably. A programme made entirely of low-load “calorie-burning” circuits may not provide the same strength-retention signal as well-designed resistance work.
2. Substrate: distribute protein across the day
Look first at normal meals: dairy or fortified alternatives, eggs, fish, lean meat, tofu, tempeh, beans, lentils and other culturally appropriate foods. Distribution across several meals is often more practical than trying to recover a low-protein day with one very large serving. Supplements are an optional convenience, not a quality badge.
3. Severity: avoid a deficit that undermines training
Rapid loss, persistent fatigue, worsening sleep, declining training performance, menstrual disturbance, dizziness or a growing preoccupation with food should not be celebrated as discipline. A trainer should pause escalation and refer appropriately. The narrow four-week trial that found benefits from very high protein during a marked deficit involved young men completing unusually intensive, supervised training; it should not be copied as a general public programme (Longland et al., 2016).
4. Signals: measure more than kilograms
Track a small set of repeatable performance markers, such as a stable exercise, submaximal repetition performance or a functional task. Interpret circumference and body-composition devices cautiously: hydration, glycogen, food intake and device error can create short-term noise. No single consumer measurement can directly prove that skeletal muscle has been preserved.
A worked example for a personal trainer
A client wants gradual weight loss while maintaining everyday strength. The trainer keeps two or three weekly resistance sessions, selects four repeatable performance markers and avoids adding large amounts of conditioning at the first plateau. The client plans a recognisable protein source at each main meal and consults a registered dietitian for an individual target because of a complex medical history.
After four weeks, body mass is trending down slowly and three performance markers are stable; one is improving. The trainer retains the plan. If body mass were falling rapidly while performance and recovery deteriorated, the correct response would not be to praise the faster loss. It would be to review the training demand and refer nutrition or medical questions to the appropriate professional.
Professional scope: what trainers should and should not do
A suitably trained fitness professional can teach general healthy-eating principles, help a client connect meals with training and monitor performance. They should not diagnose nutrient deficiency, prescribe treatment diets, or advise a client to start, stop or alter weight-loss medication. Kidney disease, eating-disorder risk, pregnancy, complex metabolic disease and unexplained symptoms require appropriately qualified clinical input.
Language also matters. Discuss strength, function, habits and health goals without moralising food or stigmatising body size. Sustainable behaviour is more useful than a perfect-looking seven-day plan that the client cannot maintain.
Evidence limitations
“Lean mass” is not identical to skeletal muscle, and measurement methods differ across studies. Trials vary in energy deficit, protein source, supervision, training status and duration. Group averages cannot determine one person’s optimum intake, and higher protein does not reliably prevent every reduction in strength or physical function. Long-term adherence and diverse dietary patterns are less well studied than short, controlled interventions.
The practical EFWA position
Do not treat protein, resistance training or the rate of weight loss as isolated levers. Build a tolerable plan, provide a progressive muscular stimulus, make protein-rich foods practically available and watch what happens to performance and recovery. The goal is not merely to make the scale move; it is to improve body composition while protecting capability.
Explore more evidence-informed resources in the EFWA Knowledge Hub, learn about EFWA’s educators on the Academic Team page, or compare professional learning pathways on the Personal Trainer Courses hub. For programming context, read Progressive Overload: What Should Personal Trainers Actually Progress?
References
- Bellicha, A., van Baak, M. A., Battista, F., Beaulieu, K., Blundell, J. E., Busetto, L., Carraça, E. V., Dicker, D., Encantado, J., Ermolao, A., Farpour-Lambert, N., Pramono, A., Woodward, E., & Oppert, J. M. (2021). Effect of exercise training on weight loss, body composition changes, and weight maintenance in adults with overweight or obesity: An overview of 12 systematic reviews and 149 studies. Obesity Reviews, 22(S4), e13256. https://doi.org/10.1111/obr.13256
- Binmahfoz, A., Dighriri, A., Gray, C., & Gray, S. R. (2025). Effect of resistance exercise on body composition, muscle strength and cardiometabolic health during dietary weight loss in people living with overweight or obesity: A systematic review and meta-analysis. BMJ Open Sport & Exercise Medicine, 11(3), e002363. https://doi.org/10.1136/bmjsem-2024-002363
- EFSA Panel on Dietetic Products, Nutrition and Allergies. (2012). Scientific opinion on dietary reference values for protein. EFSA Journal, 10(2), 2557. https://doi.org/10.2903/j.efsa.2012.2557
- Kokura, Y., Ueshima, J., Saino, Y., & Maeda, K. (2024). Enhanced protein intake on maintaining muscle mass, strength, and physical function in adults with overweight/obesity: A systematic review and meta-analysis. Clinical Nutrition ESPEN, 63, 417–426. https://doi.org/10.1016/j.clnesp.2024.06.030
- Longland, T. M., Oikawa, S. Y., Mitchell, C. J., Devries, M. C., & Phillips, S. M. (2016). Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: A randomized trial. American Journal of Clinical Nutrition, 103(3), 738–746. https://doi.org/10.3945/ajcn.115.119339
- Nunes, E. A., Colenso-Semple, L., McKellar, S. R., Yau, T., Ali, M. U., Fitzpatrick-Lewis, D., Sherifali, D., Gaudichon, C., Tomé, D., Atherton, P. J., Camprubi Robles, M., Naranjo-Modad, S., Braun, M., Landi, F., & Phillips, S. M. (2022). Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. Journal of Cachexia, Sarcopenia and Muscle, 13(2), 795–810. https://doi.org/10.1002/jcsm.12922
This article is an educational overview and does not replace individual medical or dietetic advice.
Author disclosure: Dr Onen is EFWA’s Founder and Academic Director. EFWA provides professional education in this subject area.
