Can You Bulk Up on a 16:8 Fasting Schedule?
New research finds time-restricted eating builds muscle as effectively as traditional meal timing—but with less fat gain and a slight trade-off in squat strength.
Can you build muscle and strength just as effectively while eating all your food in an 8-hour window? For lifters and physique-minded folks, the idea of time-restricted eating (TRE)—especially the popular 16:8 method—raises a big question: can you bulk up and get stronger if you’re only eating during part of the day, even when you’re in a calorie surplus? This new study puts that question to the test.
Study Aim
The study set out to determine whether a hypercaloric (10% calorie surplus), high-protein (2.2 g/kg/day) 16:8 TRE approach impacts muscle growth, strength, and body composition during 8 weeks of supervised resistance training in well-trained men and women, compared to a traditional eating schedule (FED) where calories are spread throughout the day.
Methods
Participants: 17 well-trained men (n=10) and women (n=7), all with at least a year of consistent resistance training and meeting minimum strength standards.
Design: Randomised into two groups:
TRE group: Ate all calories within an 8-hour window, starting at least 1 hour after training.
FED group: Ate the same calories, protein, carbs, and fat, but spread out across the day.
Diet: Both groups had a 10% calorie surplus and high protein (2.2 g/kg/day).
Training: Supervised progressive resistance exercise, 4 times per week for 8 weeks.
Measurements: Body composition (via BODPOD and BIS), strength (1RM for squat and bench), muscular endurance, training volume, subjective energy, mood, and sleep.
Results
Eating Window: TRE group ate within ~8 hours; FED group within ~13 hours.
Diet: Both groups matched for calories and macronutrients.
Training Volume: TRE group completed fewer total repetitions (6,960 ± 287) than FED (7,334 ± 289).
Energy Levels: The TRE group reported lower daily energy levels, especially at weeks 4 and 8.
Strength Gains: Both groups improved upper and lower body strength and muscular endurance. However, squat 1RM gains were 4.0 ± 1.9 kg lower in the TRE group.
Muscle Mass: Both groups increased fat-free mass (muscle) similarly (TRE: +2.67 kg, FED: +1.82 kg).
Fat Mass: FED group gained more fat mass (+1.4 ± 0.6 kg) than TRE.
Mood and Sleep: No significant changes in either group.
Related
Practical Takeaways
Muscle Gains: You can build muscle just as well on a 16:8 TRE schedule as with traditional eating, provided you’re in a calorie surplus and get enough protein.
Strength: Both eating patterns improve strength, but the TRE group saw slightly smaller gains in squat strength.
Training Volume: TRE may lead to slightly less total training volume, possibly due to lower energy levels during the day.
Fat Gain: TRE may help limit fat gain during a bulk compared to eating throughout the day.
Lifestyle Fit: If you prefer a shorter eating window for lifestyle or appetite reasons, TRE is a viable option for muscle growth, but be aware of possible impacts on energy and lower-body strength progress.
Key Takeaways
16:8 TRE is effective for muscle growth and strength when eating in a calorie surplus with adequate protein, even in well-trained individuals.
Slightly lower squat strength gains and training volume, as well as lower subjective energy, may occur with TRE.
TRE may help limit fat gain during bulking.
Choose the eating pattern that best fits your goals, lifestyle, and training demands. Both can work, but the small differences may matter for advanced lifters or those looking for maximal strength gains
Related
Blake DT, Hamane C, Pacheco C, Henselmans M, Tinsley GM, Costa P, Coburn JW, Campidell T, Galpin AJ. Hypercaloric 16:8 time-restricted eating during 8 weeks of resistance exercise in well-trained men and women. J Int Soc Sports Nutr. 2025 Dec;22(1):2492184. doi: 10.1080/15502783.2025.2492184. Epub 2025 Apr 16. PMID: 40241374; PMCID: PMC12006946.
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