Background: Very low-calorie diets (VLCD) are a front-line strategy, to propagate rapid weight loss in obesity and diabetes; however, a quarter of the total weight loss is in the form of lean mass, including muscle – representing a major deleterious concurrent consequence. Exercise in the form of resistance exercise training (RET) promotes muscle hypertrophy, while high-intensity interval training (HIIT) improves muscle mass more marginally but also cardiopulmonary fitness (CPF). However, no study has been conducted contrasting how RET and HIIT adjuvant to VLCD interact in relation to metabolism and body composition in humans. We therefore explored the effects of VLCD with or without RET or HIIT on body composition, muscle protein synthesis (MPS), metabolic markers, muscle strength and CPF.
Methods: Overweight and obese middle-aged (male) participants were randomly allocated into interventions of VLCD only (N=10; 46±8y; 104±12kg; BMI 32±4, (means±SD)), VLCD+RET (N=8; 40±8y; 99k±10kg; BMI 32±2) or VLCD+HIIT (N=8; 46±11y; 101±12kg; BMI 33±3). All groups received 6-weeks of VLCD meal replacement (conforming to <800kcal/d). VLCD adjuvant exercise groups received supervised training (HIIT/RET) 3X/per week. DXA scans were conducted pre-and-post interventions to assess changes in body composition. Biopsies of vastus lateralis thigh muscle were performed via conchotome methods to quantify muscle protein synthesis (MPS) using deuterium oxide (D2O) incorporation technique over the 6-week period. Lipid profiles, insulin sensitivity biomarkers, and blood pressure were assessed as markers of metabolic health. One repetition maximum (1-RM) was used to assess upper limb/lower limb strength (i.e., supine chest press, latissimus pull-down, seated row, leg curl, knee-extension, leg press), while cardiopulmonary exercise testing was used to assess CPF in the form of VO2 max and anaerobic threshold.
Results: All groups (VLCD only, VLCD+RET and VLCD+HIIT) exhibited significant weight loss (11±3 kg, 11±4kg, 12±4kg respectively), fat mass loss (7±2kg, 7±2kg, 8±3kg, and LM loss (4±2kg, 4±2kg, 4±1kg) (P<0.0001) with no between-groups difference being observed. MPS rates after the 6-weeks of intervention were 0.8%±0.2d-1, 0.9%±0.2d-1 and 1.2%±0.2d-1 for VLCD only, VLCD+RET and VLCD+HIIT, respectively – with significant differences being seen between VLCD+HIIT compared to VLCD only (P=0.004). Significant improvements were seen in insulin sensitivity biomarker indices (i.e., HOMA-IR, QUICKI, Cederholm), lipid profiles (cholesterol, triglycerides) and blood pressure (systolic and diastolic) in all groups (P<0.05), with no group differences. Only did the VLCD+RET group illustrate a significant 1-RM improvement (P<0.01), although notably the other two groups exhibited no reductions in 1-RM. No intra- or inter-group differences were observed for VO2 max/anaerobic threshold.
Conclusion: VLCD with or without adjuvant distinct exercise modes, induced marked weight loss. Despite marked LM loss all groups similarly improved metabolic biomarkers in the form of insulin indices, lipid profiles and blood pressure, with no differences between the groups. CPF was preserved in all groups. HIIT was associated with significantly higher MPS compared to VLCD only, and thus may represent a means to offset LM loss during longer-term calorie deficits. Addition of RET, while on VLCD, improved 1-RM despite reductions in LM, suggesting maintenance of muscle strength on VLCD is beyond muscle mass per se.