A randomized controlled trial was conducted to examine eight weeks of resistance training (RT) with and without time-restricted feeding (TRF) in order to assess nutrient intake and changes in body composition and muscular strength in young recreationally active males. The TRF programme consisted of consuming all calories within a four-hour period of time for four days per week, but included no limitations on quantities or types of foods consumed. The RT programme was performed three days per week and consisted of alternating upper and lower body workouts. For each exercise, four sets leading to muscular failure between 8 and 12 repetitions were employed. Research visits were conducted at baseline, four, and eight weeks after study commencement. Measurements of total body composition by dual-energy X-ray absorptiometry and muscle cross-sectional area by ultrasound were obtained. Upper and lower body strength and endurance were assessed, and four-day dietary records were collected. TRF reduced energy intake by ∼650 kcal per day of TRF, but did not affect total body composition within the duration of the study. Cross-sectional area of the biceps brachii and rectus femoris increased in both groups. Effect size data indicate a gain in lean soft tissue in the group that performed RT without TRF (+2.3 kg, d = 0.25). Upper and lower body strength and lower body muscular endurance increased in both groups, but effect sizes demonstrate greater improvements in the TRF group. Overall, TRF reduced energy intake and did not adversely affect lean mass retention or muscular improvements with short-term RT in young males.
Keywords: Intermittent fasting; body composition; energy intake; muscular strength; resistance training; time-restricted feeding.