The effects of a 4-week protein overfeeding protocol on body composition and influence of FTO genotype in exercise-trained men and women
Study Details
This 4-week intervention examined whether modest protein overfeeding altered body composition in 35 exercise-trained men and women who completed pre- and post-testing 🔍
Participants were asked to increase protein intake by ~20% while maintaining habitual training and keeping carbohydrate and fat intake similar 🥩
Key Findings
📈 Actual protein intake increased by ~12%, from 1.93 → 2.12 g/kg/day (+18 g/day)
⚖️ Total energy intake increased by only ~51 kcal/day and did not change significantly
💪 Lean body mass increased by +0.67 kg over 4 weeks
💧 Total body water also increased by +0.49 L, which is important because body composition was measured using bioelectrical impedance
↔️ Fat mass did not significantly change (+0.37 kg), while body fat percentage also remained statistically unchanged
📊 Total body mass increased by ~0.57 kg, but this did not reach statistical significance
🧬 Researchers also examined the obesity-associated FTO rs9939609 genotype, but risk-allele status did not predict changes in lean mass, fat mass, body weight or body fat percentage
🏋️ Importantly, participants already had relatively high baseline protein intakes and averaged ~5 h/week of resistance training
⚠️ The study had no control group, only 35 of 56 participants completed the intervention, dietary intake was self-reported and BIA is sensitive to hydration status
Conclusion
For trained athletes already consuming plenty of protein, a modest increase from ~1.9 to ~2.1 g/kg/day may support small increases in lean mass without promoting fat gain, although the rise in body water and lack of a control group mean the true magnitude of muscle gain remains uncertain ✅
Reference
https://www.tandfonline.com/doi/full/10.1080/15502783.2026.2744348
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