In obese women on a very low-calorie diet for 90 days while doing resistance training, the size of both slow-twitch and fast-twitch muscle fibers in the thigh increased, even though they lost 16 kilograms of body weight.
See the scientific wording
In obese females undergoing severe energy restriction (3360 kJ/day for 90 days) with resistance training, the cross-sectional area of both slow-twitch and fast-twitch muscle fibers in the vastus lateralis significantly increased despite an average total weight loss of 16 kg.
Strong evidence
Randomized trialsOne moderate-quality study supports this claim, so treat this as an early signal rather than settled science.
What the research says
1 study reviewedSupporting (1)
Muscle hypertrophy with large-scale weight loss and resistance training.
Randomized Controlled TrialHuman1993
When obese women ate very few calories and lifted weights, their thigh muscles got bigger — even though they lost a lot of weight. Those who didn’t lift weights didn’t gain muscle. So, lifting weights can help you build muscle even while dieting hard.
Contradicting (0)
No contradicting studies found yet
That doesn't mean it's settled — it just means no study has tested the opposite.
Quality-weighted scoring: we follow the GRADE framework — each study is rated High, Moderate, Low, or Very Low based on study design, methodology rigor, and risk of bias. A single high-quality RCT can outweigh several weaker observational studies.
Scores reflect study quality, not just count.
When muscles are pulled hard during weight lifting, sensors in the muscle fibers trigger a chain reaction that tells the cell to build more muscle proteins, even when the body is in a state of extreme calorie shortage. This buildup of proteins makes the muscle fibers thicker, despite the body losing weight overall.
Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting study
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In obese women on a very low-calorie diet for 90 days while doing resistance training, the size of both slow-twitch and fast-twitch muscle fibers in the thigh increased, even though they lost 16 kilograms of body weight.
Mechanism
1 studyLifting weights pulls on muscle fibers hard enough to turn on a built-in signal that tells the muscle to make more proteins, even when the body is starving for energy. This extra protein builds up inside the fibers, making them thicker, which is why muscles grow bigger even as the body loses weight.
When muscles are pulled hard during weight lifting, sensors in the muscle fibers trigger a chain reaction that tells the cell to build more muscle proteins, even when the body is in a state of extreme calorie shortage. This buildup of proteins makes the muscle fibers thicker, despite the body losing weight overall.
Mechanical tension from resistance exercise activates integrin and focal adhesion kinase signaling in muscle fibers
Mechanotransduction triggers PI3K/Akt/mTORC1 signaling pathway activation, promoting ribosomal biogenesis and translation initiation
Increased protein synthesis exceeds proteolysis, leading to net accretion of contractile proteins (actin, myosin) and sarcomere addition
Evidence from Studies
Supporting (1)
Community contributions welcome
Muscle hypertrophy with large-scale weight loss and resistance training.
When obese women ate very few calories and lifted weights, their thigh muscles got bigger — even though they lost a lot of weight. Those who didn’t lift weights didn’t gain muscle. So, lifting weights can help you build muscle even while dieting hard.
Contradicting (0)
Community contributions welcome
Score Breakdown
No multi-axis breakdown available yet. The overall Pro / Against score above is the best signal.
- No clinical evidence is available; the score reflects mechanistic plausibility only.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Systematic Review of Resistance Training and Severe Energy Restriction on Muscle Fiber Cross-Sectional Area in Obese Women
Population: Obese adult females; Intervention: Resistance training combined with energy restriction at 3360 kJ/day for 90 days; Comparator: Energy restriction without resistance training or no intervention; Outcome: Change in vastus lateralis slow-twitch and fast-twitch muscle fiber cross-sectional area via biopsy; Duration: 90 days.
Randomized Controlled Trial of Resistance Training vs. No Training During 90-Day Severe Energy Restriction in Obese Women
Population: Obese adult females; Intervention: Resistance training plus 3360 kJ/day diet; Comparator: 3360 kJ/day diet without resistance training; Outcome: Change in vastus lateralis slow-twitch and fast-twitch muscle fiber cross-sectional area via biopsy; Duration: 90 days; Design: Double-blind, randomized, parallel-group.
Prospective Cohort Study of Muscle Fiber Adaptations in Obese Women Undergoing 90 Days of Severe Energy Restriction with Resistance Training
Population: Obese adult females; Intervention: Resistance training and 3360 kJ/day diet over 90 days; Comparator: None (single group); Outcome: Pre- and post-intervention measurement of vastus lateralis muscle fiber cross-sectional area; Duration: 90 days; Design: Prospective longitudinal observation.
Cross-Sectional Analysis of Muscle Fiber Size in Obese Women After 90 Days of Severe Energy Restriction with Resistance Training
Population: Obese adult females; Intervention: History of 90 days of 3360 kJ/day diet with resistance training; Comparator: Obese females with no resistance training during energy restriction; Outcome: Single-time-point measurement of vastus lateralis muscle fiber cross-sectional area; Duration: Post-intervention only.
Case Report of Muscle Fiber Hypertrophy in an Obese Female During 90 Days of Severe Energy Restriction and Resistance Training
Population: Single obese female; Intervention: 3360 kJ/day diet and resistance training for 90 days; Outcome: Pre- and post-intervention muscle biopsy showing increased slow-twitch and fast-twitch fiber cross-sectional area; Duration: 90 days.