Novel Combination of Exercise and Carbohydrate Restriction for Metabolic Health

Abstract

Purpose: To compare the effects of iso-time and quasi iso-effort high-intensity interval training (HIIT), resistance training (RT) or both HIIT and RT (COMBO), all with a low carbohydrate high fat diet (LCHF) in sedentary and overweight individuals. Methods: 54 adults (18-60 y, M=24, F=30) were randomised to one of three experimental groups: LCHF+HIIT, LCHF+RT or LCHF+COMBO. For 12 weeks the participants performed their 20 min exercise protocol thrice weekly, while following the LCHF diet (≤100 g CHO, ⁓1.5g PRO/kg and unrestricted fat intake). Sessions involved 10x1 min of high-intensity effort (⁓17 RPE on a 6-20 scale) interspersed with 1 min recovery periods. Target heart rate for HIIT was ≥95% HRR whereas for RT, resistance was set @ ⁓70-80% of maximum, or approximately 2 repetitions short of failure. Outcomes assessed were body composition, blood biomarkers, and performance measures. Results: Adjusted between group differences were analysed with general or generalised linear models. Improvements in HbA1c were significantly greater for LCHF+HIIT than both LCHF+RT (β= 2.41, p=0.014) and LCHF+COMBO (β= 2.58; p=0.005). Body mass reduction was significantly greater for LCHF+HIIT relative to LCHF+COMBO (β= 1.88, p=0.049). Upper body strength was superior for LCHF+RT relative to LCHF+HIIT (β= 4.18; p=0.024). Resting metabolic rate (RMR) was greater for LCHF+COMBO (β= 896.02; p=0.004) and LCHF+RT (β= 690; p=0.024) both relative to LCHF+HIIT. Otherwise, there were no significant differences between groups observed. Conclusion: These combinations of LCHF and exercise were similarly effective for improving cardiometabolic risk factors, potentially due to the high-intensity effort elicited in all three conditions, and the LCHF