Author(s): DISSEMOND, J., GAVANDA, S., HELD, S., HAVERS, T., WIEWELHOVE, T., BRINKMANN, C., GEISLER, S., LÖFFLER, D., ARNET, L., ISENMANN, E., Institution: IST UNIVERSITY OF APPLIED SCIENCES, Country: GERMANY, Abstract-ID: 911

INTRODUCTION:
A hypercaloric diet is commonly used during resistance training to promote muscle hypertrophy but often increases body weight (BW) and fat mass (FM), potentially causing adverse metabolic effects. Time-restricted eating (TRE), particularly 16:8 (TRE16:8), may mitigate these effects. Evidence on TRE16:8 under hypercaloric conditions in resistance-trained individuals is limited. This study investigated the effects of TRE16:8 on strength, body composition, glucose metabolism, and dietary intake during a hypertrophy phase.
METHODS:
In a 12-week randomized controlled trial, 23 healthy, resistance-trained adults (29.9±8.6 years; 17 men, 6 women) were assigned to either a TRE group (TRE16:8; n=11) or a control group (CG; n=12). Both groups followed a standardized resistance training program (3 sessions/week) and consumed a hypercaloric diet (+300–500 kcal/day). Every four weeks (T0–T3), one-repetition maximum (1RM) in the bench press (BP) and deadlift (DL), BW, fat-free mass (FFM), muscle mass (MM), and FM were assessed. Dietary intake was recorded using the FDDB app and analyzed with EBISpro. Blood parameters related to glucose metabolism (HbA1c, fasting glucose, insulin, and HOMA-IR) were measured pre- and post-intervention. Data were analyzed using linear mixed-effects models.
RESULTS:
Both groups significantly improved maximal strength in the BP (TRE16:8, 12.95±7.23kg; CG, 11.04±3.61kg; p<0.001) and DL (TRE16:8, 26.36±10.92kg; CG, 26.04±8.01kg; p<0.001) as well as FFM (TRE16:8, 1.34±0.78kg; CG, 1.38±1.42kg; p<0.001) and MM (TRE16:8, 1.07±0.94kg; CG, 1.13±0.61kg; p<0.001) with no significant differences between groups. BW (TRE16:8, 2.19±2.40kg; CG, 3.90±2.14kg) and FM (TRE16:8, 2.00±2.49kg; CG, 4.38±2.26kg) increased in both groups. However, these increases were significantly smaller in the TRE16:8 compared to the CG (BW: p=0.018; FM: p=0.009).
Dietary records (n=18) showed TRE16:8 consumed fewer carbs (p=0.002), protein (p=0.038), and energy (p=0.003) than planned. Between-group comparisons showed significant differences in energy intake (p=0.015) and carbohydrate intake relative to FFM (p=0.027). Furthermore, significant time*group interactions were observed for markers of glycemic control. The TRE16:8 group exhibited reductions in HbA1c and fasting insulin, whereas these parameters increased in the control group (HbA1c: p=0.001; insulin: p=0.045), indicating improved glucose homeostasis.


CONCLUSION:
TRE16:8 resulted in comparable gains in 1RM strength, MM, and FFM compared with a conventional hypercaloric diet during a bulking phase, while attenuating increases in BW and FM. Additionally, TRE16:8 was associated with more favorable glycemic markers. Notably, the time-restricted eating window naturally limited energy intake despite a prescribed hypercaloric diet. These findings suggest that TRE16:8 is a pragmatic and effective nutritional strategy during a muscle-building phase, enabling sufficient anabolic adaptations while constraining excessive energy surplus and fat gain.