The Effect Of Continuous Energy Restriction Vs Intermittent Fasting, With Resistance Training, On Lean Mass

Abstract

PURPOSE: To determine if two energy restricted diets (continuous energy restriction (CER) and 5:2 intermittent fasting (IF)) combined with resistance training (RT) results in lean body mass (LBM) retention while reducing bodyweight. METHODS: Thirty-four young, untrained males and females were randomised to undertake the following diets for 12 weeks: CER (consume 80% of estimated energy requirements (EER) every day), or IF (consume approximately 30% of EER twice per week on fast days and 100% of EER every other day). Fast days included meals of protein shakes, a soup and vegetables. Both groups aimed to be isocaloric with an average energy restriction of 20% EER, and isonitrogenous consuming an average protein intake of 1.5 grams per kilogram of bodyweight per day. Both groups completed 2 supervised RT sessions and 1 unsupervised workout per week. The IF group completed their exercise on non-fast days. Body composition was assessed by dual x-ray absorptiometry. Data was analysed using an intention-to-treat linear mixed model, assuming AR(1) dependence across time. In addition, a change analysis was conducted for participants who completed both the baseline and 12 week assessments. RESULTS: For females, bodyweight was significantly reduced (mean decrease 3.1%, p=0.009), and LBM significantly increased (mean increase 5.8%, p<0.001), with no difference observed between diets. Similarly for men, there was no significant diet effect on bodyweight; both groups experienced an overall reduction of 6.3% (p<0.001). Combined, men in both diet groups experienced a significant increase in LBM (mean increase 1.4%, p=0.021), however there was a trend towards a greater increase in LBM in the IF compared to the CER group (mean increase CER = 0.7%, IF = 2.0%). CONCLUSIONS: Across both diet groups, males and females experienced a significant reduction in bodyweight while, on average, increasing LBM. Neither diet was more effective for bodyweight reduction, however there was a trend towards greater LBM accrual in IF compared to CER males. Gender specific responses to the intervention were evident, with a greater increase in LBM for females. Moderate energy restriction with high protein intake and RT can lead to concomitant weight loss and LBM accrual.