For years you heard it: you either gain muscle or you lose fat. Studies have shown for a while that both at once is possible, and a 2026 trial adds another data point.
Short answer: For many people who train, especially beginners and people returning after a break, it is possible. It does not work for everyone, and not at the same speed. In the Vargas-Molina 2026 study (30 resistance-trained adults, 10 weeks, measured with a DXA scan), the group eating in a moderate calorie deficit lost 2.94 kg of fat and gained 1.04 kg of fat-free mass.
What the study found
Thirty resistance-trained adults, average age 23, trained four days a week for 10 weeks. Body composition was measured with DXA, a body scan. Two groups got a food plan with high protein (2.5 g per kg of body weight). The third group trained the same way but ate as usual.
- Deficit group (moderate calorie deficit): -2.94 kg of fat, +1.04 kg of fat-free mass.
- Maintenance group: -1.41 kg of fat, +0.97 kg of fat-free mass.
- Control group (same training, no supervision of food): no meaningful change.
The difference in fat loss between the deficit and maintenance groups was not statistically significant, and both groups gained a similar amount of fat-free mass. Fat-free mass on a DXA scan includes muscle, but also water, glycogen and organs, so it is not a direct muscle measurement. This was also a small study, 10 people per group. Treat it as an early signal and no more than that. A 2022 meta-analysis puts this in context: on average, people in a deficit gained less lean mass than people training without one, while strength gains were similar.
The energy maths still holds
This does not break thermodynamics. Every kilogram of body fat holds roughly 7,700 kcal. In a mild deficit your body takes its energy from there. When it also gets a strength stimulus and enough protein, the energy from fat stores can cover part of the cost of building muscle, while the building material comes from the protein you eat. That is ordinary physiology.
Do not steer by the scale
Do not expect the number on the scale to go down in a straight line. Glycogen, water and salty meals can move it by a kilo or two from day to day (more in why your weight fluctuates). When you recomp, which means you lose fat and gain muscle at the same time, track measurements, photos and your performance in the gym.
The conditions
It works best under a few conditions:
- Strength training with progressive overload, about 3 to 5 times a week.
- Protein 1.6-2.2 g/kg. The studies above used 2.4-2.5 g/kg, but for most people 1.6-2.2 g/kg is enough. The upper end works more as insurance than as extra building material.
- A mild deficit of about 10 to 20%. A larger deficit can still work short term with very high protein and hard training (Longland 2016), but a 2022 meta-analysis found that deficits above roughly 500 kcal a day tend to block lean mass gains (Murphy & Koehler 2022).
- Enough sleep to recover and stick to the plan, for most adults seven hours or more (see sleep and fat loss).
Who gets it fastest
In my practice it tends to come fastest for beginners, people who come back after a break, and people with a higher body fat percentage. An advanced lifter close to their ceiling may progress faster with the classic cycles of gaining and cutting.
Frequently asked questions
What are the conditions for this to work?
It works best with: strength training with progressive overload about 3 to 5 times a week, protein 1.6-2.2 g/kg, a mild deficit of about 10 to 20% (larger deficits tend to limit muscle gain), and enough sleep to recover well. The upper end of the protein range works more as insurance than as extra building material.
Who builds muscle fastest in a deficit?
In my practice it tends to come fastest for beginners, people who come back after a break, and people with a higher body fat percentage. An advanced lifter close to their ceiling may progress faster with the classic cycles of gaining and cutting.
How can the body build muscle when energy is short?
Every kilogram of body fat holds roughly 7,700 kcal, and in a mild deficit your body takes energy from there. When it also gets a strength stimulus and enough protein, the energy from fat stores can cover part of the cost of building muscle, while the building material comes from the protein you eat.
How do I know a recomposition is working?
Do not go by the number on the scale, because glycogen, water and salty meals can move it by a kilo or two from day to day. Track measurements, photos and your performance in the gym.
How did the other groups in the study do?
The maintenance group lost 1.41 kg of fat and gained 0.97 kg of fat-free mass. The difference in fat loss compared with the deficit group was not statistically significant. The control group, with the same training but no supervision of food, showed no meaningful change.
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Apply for coaching Get the free Fat Loss KitSources, so you can check:
1) Vargas-Molina S, et al. Comparison of two nutritional protocols in body re-composition of resistance-trained participants. Eur J Appl Physiol. 2026;126(7):4019-4030. DOI: 10.1007/s00421-026-06209-6 | PMID: 41940947
2) Slater GJ, et al. Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training. Front Nutr. 2019;6:131. DOI: 10.3389/fnut.2019.00131 | PMID: 31482093
3) Longland TM, et al. 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. Am J Clin Nutr. 2016;103(3):738-746. DOI: 10.3945/ajcn.115.119339 | PMID: 26817506
4) Murphy C, Koehler K. Energy deficiency impairs resistance training gains in lean mass but not strength: a meta-analysis and meta-regression. Scand J Med Sci Sports. 2022;32(1):125-137. DOI: 10.1111/sms.14075 | PMID: 34623696
Martin Barna
Online nutrition and fitness coach. Since 2013 I have coached 600+ clients through fat loss and keeping it off. Evidence-based coaching.
Apply for coachingThis article is for information only. It is not medical advice. If you have a health condition, talk to your doctor.