Intermittent fasting and continuous energy restriction result in similar changes in body composition and muscle strength when combined with a 12 week resistance training program

Abstract

Purpose The objective of this study was to compare the effects of 12 weeks of resistance training combined with either 5:2 intermittent fasting or continuous energy restriction on body composition, muscle size and quality, and upper and lower body strength. Methods Untrained individuals undertook 12 weeks of resistance training plus either continuous energy restriction [20% daily energy restriction (CERT)] or 5:2 intermittent fasting [~ 70% energy restriction 2 days/week, euenergetic consumption 5 days/week (IFT)], with both groups prescribed a mean of ≥ 1.4 g of protein per kilogram of body weight per day. Participants completed 2 supervised resistance and 1 unsupervised aerobic/resistance training combination session per week. Changes in lean body mass (LBM), thigh muscle size and quality, strength and dietary intake were assessed. Results Thirty-four participants completed the study (CERT = 17, IFT = 17). LBM was significantly increased (+ 3.7%, p < 0.001) and body weight (− 4.6%, p < 0.001) and fat (− 24.1%, p < 0.001) were significantly reduced with no significant difference between groups, though results differed by sex. Both groups showed improvements in thigh muscle size and quality, and reduced intramuscular and subcutaneous fat assessed by ultrasonography and peripheral quantitative computed tomography (pQCT), respectively. The CERT group demonstrated a significant increase in muscle surface area assessed by pQCT compared to the IFT group. Similar gains in upper and lower body strength and muscular endurance were observed between groups. Conclusion When combined with resistance training and moderate protein intake, continuous energy restriction and 5:2 intermittent fasting resulted in similar improvements in body composition, muscle quality, and strength. ACTRN: ACTRN12620000920998, September 2020, retrospectively registered.

The Effects of Intermittent Fasting and Continuous Energy Restriction with Exercise on Cardiometabolic Biomarkers, Dietary Compliance, and Perceived Hunger and Mood: Secondary Outcomes of a Randomised, Controlled Trial

“…Hutchison and colleagues [ 33 ] observed increased fasting insulin levels when measured after a fed day (although decreased levels after a fasted day) following 8 weeks of alternate-day fasting in individuals who were prescribed a protocol designed to maintain weight. The participants in the Hutchison study, who were, on average, much older than the participants in the current analysis (~50 vs. ~24 years old) did show similar modest weight loss compared to the IFT women in our group (~2.7 kg; see previously published findings [ 21 ]), and this could explain the lack of beneficial effects on glucose regulation. Hutchison et al [ 33 ] included another energy-restricted alternative day fasting intervention group that experienced greater amounts of weight loss (5.4 kg), who experienced significant reductions in fasting insulin when measured after both a fed and fasted day.…”

“…Detailed intervention methods have been previously described [ 21 ]. Briefly, 34 generally healthy (17 men and 17 women), recreationally active but untrained individuals with a BMI of 22.0–35.0 kg/m 2 aged between 18 and 35 years were randomised to undertake 12 weeks of resistance training (3 sessions per week; two 45-minute supervised session and one 30-minute unsupervised session) and either a continuous energy restriction (CERT group) or 5:2 intermittent fasting (IFT group) diet.…”

“…In order to assess dietary intake, participants were asked to complete a 3-day food diary using a mobile phone application during weeks 1, 6 and 12. Results of are reported in the primary outcomes study for this intervention [ 21 ]. The original study was powered to detect differences in the primary outcome (lean body mass).…”

“…The purpose of this study is to present secondary outcomes from a 12-week randomised, controlled trial investigating the impact of isocaloric 5:2 IF and CER diets paired with resistance training on body composition in untrained young adults [ 21 ]. The aim of this secondary data analysis is to determine the effects of both interventions on cardiometabolic health markers, as well as the impact on self-reported dietary compliance, perceived hunger, cravings, mood and energy levels.…”

Early Time-Restricted Eating Reduces Weight and Improves Glycemic Response in Young Adults: A Pre-Post Single-Arm Intervention Study

“…High-protein diets have been suggested as a strategy to preserve lean body mass during a period of weight loss [ 19 ]. A 12-week intervention of intermittent fasting, resistance training, and a prescribed daily protein intake of more than 1.4 g per kg body weight has been shown to significantly reduce body weight and fat mass while also increasing lean body mass [ 24 ].…”