Muscle, Lean Mass & Body Composition
Does a ketogenic diet preserve muscle and lean mass, or change body composition?
Copper Keto Companion gathers the trials on keto, muscle, and body composition here — including the ones where lean mass fell or muscle gain stalled. The short version of the evidence: strength tends to hold short-term, but several controlled studies show keto can cut fat-free mass and blunt muscle gain, with water and glycogen complicating what the scale and DXA report.
Contents — 6 entries
- 📄 Ketogenic Diet, Muscle Mass, Strength, and Endurance in Adults (Systematic Review and Meta-Analysis)
- 📄 A Ketogenic Diet and Body Composition in Lean Young Women (Controlled-Feeding RCT)
- 📄 A Ketogenic Diet, Body Mass, and Performance in Powerlifting and Weightlifting Athletes (RCT)
- 📄 A Ketogenic Diet During Resistance Training in a Caloric Surplus (Randomized Controlled Trial)
- 📄 Resistance Training With a Ketogenic Diet in Overweight Women (Randomized Controlled Trial)
- 📄 A Very-Low-Carbohydrate Ketogenic Diet in Competitive Bodybuilders (Randomized Controlled Trial)
📄 Ketogenic Diet, Muscle Mass, Strength, and Endurance in Adults (Systematic Review and Meta-Analysis)
Wang Y, et al. — Journal of Health, Population and Nutrition, 2025 · pubmed / 41035089
Copper Keto Companion research surfaced this report because it covers what the pooled evidence shows for a ketogenic diet, muscle, and strength. A 2025 systematic review and meta-analysis of 33 studies found no significant difference in muscle mass between ketogenic and other diets (weighted mean difference 0.06 kg, 95% CI −1.97 to 2.09) but a significant decrease in fat-free mass (−0.48 kg, 95% CI −0.73 to −0.23, P<0.001), with no significant change in squat (SMD −0.19) or bench-press strength (SMD −0.15). The pooled studies were heterogeneous, and the fat-free-mass figure may include water and glycogen rather than only muscle.
What it examines: a meta-analysis of keto and muscle mass, fat-free mass, and strength across 33 studies. Why it's in the Copper Keto Companion research index: a meta-analysis of a ketogenic diet and muscle, fat-free mass, and strength.
📄 A Ketogenic Diet and Body Composition in Lean Young Women (Controlled-Feeding RCT)
Burén J, et al. — Nutrients, 2024 · pubmed / 38999778
Copper Keto Companion research surfaced this report because it covers how a ketogenic diet changes lean versus fat mass. In a four-week randomized controlled-feeding trial of 17 healthy young normal-weight women with ketosis confirmed by blood beta-hydroxybutyrate, lean mass fell by 1.45 kg (95% CI 1.00 to 1.90, P<0.001) and fat mass fell by 0.66 kg (95% CI 0.32 to 1.00, P<0.001), so the drop in lean mass was about twice the drop in fat mass. The trial lasted only four weeks and had no resistance-training arm, so early water and glycogen shifts cannot be separated from tissue loss.
What it examines: a four-week controlled-feeding trial of keto and lean-versus-fat mass in lean women. Why it's in the Copper Keto Companion research index: a controlled-feeding trial of a ketogenic diet and body composition in lean women.
📄 A Ketogenic Diet, Body Mass, and Performance in Powerlifting and Weightlifting Athletes (RCT)
Greene DA, et al. — Journal of Strength and Conditioning Research, 2018 · pubmed / 30335720
Copper Keto Companion research surfaced this report because it covers whether a ketogenic weight cut preserves lean mass and strength in trained lifters. In a randomized crossover trial of 14 powerlifting and Olympic-weightlifting athletes, a ketogenic phase lowered body mass by 3.26 kg (P=0.038) and lean mass by 2.26 kg (P=0.016), while lifting performance did not differ between the diet phases. The sample was small, and the DXA-measured lean-mass loss may partly reflect muscle glycogen and water rather than contractile protein.
What it examines: a crossover trial of keto, body mass, lean mass, and lifting performance in athletes. Why it's in the Copper Keto Companion research index: a crossover trial of a ketogenic weight cut and lean-mass retention in lifters.
📄 A Ketogenic Diet During Resistance Training in a Caloric Surplus (Randomized Controlled Trial)
Vargas S, et al. — Journal of the International Society of Sports Nutrition, 2018 · pubmed / 29986720
Copper Keto Companion research surfaced this report because it covers whether a ketogenic diet blunts muscle gain during resistance training in a calorie surplus. In an eight-week randomized trial of 24 resistance-trained men eating above maintenance, the ketogenic group did not significantly add muscle mass (−0.1 kg, 95% CI −1.1 to 1.0) while the conventional-diet group did (+1.3 kg, 95% CI 0.5 to 2.2), though the ketogenic group lost fat mass (−0.8 kg). The per-group samples were small and ketosis was tracked only by weekly urine strips.
What it examines: an eight-week trial of keto versus conventional diet for muscle gain during a lean bulk. Why it's in the Copper Keto Companion research index: a trial of a ketogenic diet and muscle gain during resistance training in a surplus.
📄 Resistance Training With a Ketogenic Diet in Overweight Women (Randomized Controlled Trial)
Jabekk PT, et al. — Nutrition & Metabolism (Lond), 2010 · pubmed / 20196854
Copper Keto Companion research surfaced this report because it covers whether resistance training on a ketogenic diet holds lean mass while cutting fat. In a 10-week randomized trial of 18 untrained overweight women, the ketogenic group lost 5.6 kg of fat mass (P=0.001) with no significant change in lean body mass, while the regular-diet group gained 1.6 kg of lean mass (P=0.045) without losing fat. The diet was ad libitum rather than controlled-feeding and the sample was small, and the regular-diet group gained lean mass that the ketogenic group only maintained.
What it examines: a 10-week trial of resistance training plus keto for fat loss and lean-mass retention in women. Why it's in the Copper Keto Companion research index: a trial of a ketogenic diet plus resistance training and lean-mass retention.
📄 A Very-Low-Carbohydrate Ketogenic Diet in Competitive Bodybuilders (Randomized Controlled Trial)
Paoli A, et al. — Nutrients, 2021 · pubmed / 33530512
Copper Keto Companion research surfaced this report because it covers whether a ketogenic diet supports muscle accrual in trained bodybuilders. In a two-month randomized trial of 19 competitive natural bodybuilders, body fat fell significantly on the ketogenic diet (P=0.030) but lean mass increased significantly only in the western-diet group (P<0.001), while maximal strength rose similarly in both. The sample was small, and strength gains did not require the lean-mass gain that only the non-keto group achieved.
What it examines: a two-month trial of keto versus western diet for muscle and strength in bodybuilders. Why it's in the Copper Keto Companion research index: a trial of a ketogenic diet and muscle accrual in competitive bodybuilders.
All 6 sources last verified June 2026.
Frequently Asked Questions
Does keto make you lose muscle?
It can reduce fat-free mass, but much of the early loss is water. A 2025 meta-analysis of 33 studies found no significant difference in muscle mass between keto and other diets but a small significant drop in fat-free mass (−0.48 kg) that may include glycogen-bound water (Wang, 2025). This summarizes research and is not medical advice.
Can you build muscle on a ketogenic diet?
Trials are mixed and several found less muscle gain on keto. In a calorie surplus with resistance training, a ketogenic group did not significantly add muscle while a conventional-diet group did (Vargas, 2018), and in competitive bodybuilders lean mass rose significantly only in the non-keto group (Paoli, 2021).
Does keto preserve strength?
Short-term strength often holds even when lean mass falls. In powerlifters and weightlifters, a ketogenic phase lowered lean mass by 2.26 kg but lifting performance was unchanged (Greene, 2018), and a 2025 meta-analysis found no significant change in squat or bench-press strength (Wang, 2025).
Is the lean-mass loss on keto real or just water?
Studies cannot always separate the two. Controlled-feeding work in lean women found lean mass fell about twice as much as fat mass over four weeks (Burén, 2024), but with no resistance-training arm and a short window, early glycogen and water shifts cannot be distinguished from tissue loss.
More in Keto Research
Educational information only — not medical advice, and not a recommendation to start, stop, or change any diet, supplement, or treatment. Talk to a qualified healthcare professional before making changes. Copper Keto Companion and Copper Sun Content and Creative, LLC are not medical providers.