Exercise Preserves Lean Mass and Performance during Severe Energy Deficit: The Role of Exercise Volume and Dietary Protein Content

Abstract

The loss of fat-free mass (FFM) caused by very-low-calorie diets (VLCD) can be attenuated by exercise. The aim of this study was to determine the role played by exercise and dietary protein content in preserving the lean mass and performance of exercised and non-exercised muscles, during a short period of extreme energy deficit (~23 MJ deficit/day). Fifteen overweight men underwent three consecutive experimental phases: baseline assessment (PRE), followed by 4 days of caloric restriction and exercise (CRE) and then 3 days on a control diet combined with reduced exercise (CD). During CRE, the participants ingested a VLCD and performed 45 min of one-arm cranking followed by 8 h walking each day. The VLCD consisted of 0.8 g/kg body weight/day of either whey protein (PRO, n = 8) or sucrose (SU, n = 7). FFM was reduced after CRE (P < 0.001), with the legs and the exercised arm losing proportionally less FFM than the control arm [57% (P < 0.05) and 29% (P = 0.05), respectively]. Performance during leg pedaling, as reflected by the peak oxygen uptake and power output (Wpeak), was reduced after CRE by 15 and 12%, respectively (P < 0.05), and recovered only partially after CD. The deterioration of cycling performance was more pronounced in the whey protein than sucrose group (P < 0.05). Wpeak during arm cranking was unchanged in the control arm, but improved in the contralateral arm by arm cranking. There was a linear relationship between the reduction in whole-body FFM between PRE and CRE and the changes in the cortisol/free testosterone ratio (C/FT), serum isoleucine, leucine, tryptophan, valine, BCAA, and EAA (r = -0.54 to -0.71, respectively, P < 0.05). C/FT tended to be higher in the PRO than the SU group following CRE (P = 0.06). In conclusion, concomitant low-intensity exercise such as walking or arm cranking even during an extreme energy deficit results in remarkable preservation of lean mass. The intake of proteins alone may be associated with greater cortisol/free testosterone ratio and is not better than the ingestion of only carbohydrates for preserving FFM and muscle performance in interventions of short duration.

Keywords: VLCD; exercise; obesity; sucrose; very-low-calorie diet; whey protein.

Figure 1

Schematic illustration of the experimental protocol. PRE, baseline tests; CRE, caloric restriction (13.4 kJ/day) and exercise (45 min arm cranking and 8 h walking per day), for 4 days; CD: 3 days on a diet, isoenergetic with that observed during the PRE phase + reduced exercise; DXA, dual-energy x-ray absorptiometry; IPAQ, international physical activity questionnaire.

Figure 2

Assessment of changes in lean mass (fat-free mass—bone mass) by dual-energy x-ray absorptiometry. PRE, baseline tests; CRE, caloric restriction (13.4 kJ/day) and exercise (45 min arm cranking and 8 h walking per day) for 4 days; CD: 3 days on a diet isoenergetic with that consumed during the PRE phase + reduced exercise. The vertical bars represent the mean values and the error bars the standard error of the mean. Sucrose: in dark colors (n = 7) and whey protein: in light colors (n = 8). ^*P < 0.05 compared to PRE; ^†P < 0.05 compared to CRE; ^&P < 0.05 arms compared to legs.

Figure 3

Changes in performance. Assessment of changes in peak power output (Wpeak) and peak oxygen uptake (VO₂peak) in absolute and relative values (LM, lean mass) during two-legged pedaling (A–D), one-arm cranking with the control arm (E–H), and one-arm cranking with the trained arm (I–L). PRE, baseline tests; CRE, caloric restriction (13.4 kJ/day) and exercise (45 min arm cranking and 8 h walking per day) for 4 days; CD, 3 days on a diet isoenergetic with that consumed during the PRE phase + reduced exercise. The vertical bars represent the mean values and the error bars the standard error of the mean. Sucrose (n = 7) and whey protein group (n = 8). ^*P < 0.05 compared to PRE; ^†P < 0.05 compared to CRE; ^$P < 0.05 sucrose compared to whey protein; ^aP < 0.05 compared to CRE (time main effect); ^bP < 0.05 compared to CD (time main effect).