| While diet-induced weight loss is a common method for the reduction of excess fat-mass, there is also a concomitant reduction in lean fat-free mass. This loss of lean muscle mass could exacerbate the loss of muscle mass, i.e. sarcopenia, that normally occurs in older men and women. However, the effects of intentional diet-induced weight loss on the loss of muscle mass in older adults have not been elucidated. Purpose. The purpose of this study was to investigate the effects of diet-induced weight loss, alone and in combination with moderate aerobic exercise, on skeletal muscle mass in older adults. Methods. Twenty-nine overweight (BMI=31.81+/-3.37kg/m 2) older (67.23+/-4.2years) men (n=13) and women (n=16) completed a 4-month intervention consisting of diet-induced weight loss (WL) with or without or exercise (WL/EX). The WL intervention consisted of a 10% reduction in total body weight (kg) through a caloric restriction of 500-1000kcal/day. The WL/EX group achieved the same weight loss and exercised 3-5 times a week, 35-45 minutes, at a heart rate 65-75% of maximal predicted. Whole body DEXA, thigh computed tomography (CT) and a percutaneous muscle biopsy on the left vastus lateralis were collected to assess changes in skeletal muscle mass. Results. Mixed ANOVA demonstrated both groups had decreases in mean bodyweight (WL, -9.2%; WL/EX, -9.1%) and whole body fat mass (WL, -17%; WL/EX, -21%). However, whole body fat-free mass decreased in the WL (-4%) and didn't change in the WL/EX (-1%). Similarly, Type I muscle fiber area decreased in the WL (-19%) and remained unchanged in the WL/EX (3%). Type IIA fiber area decreased in both groups (WL, -15%; WL/EX, -8%). There was no change in Type IIX fiber area between WL and WL/EX. Thigh muscle cross-sectional area by CT decreased in both groups (WL, -5%; WL/EX, -4%). Conclusion. Diet-induced weight loss in the absence of increased physical activity significantly decreased fat-free muscle mass in older adults. Further, the addition of moderate aerobic exercise to intentional weight loss attenuated or prevented the loss of muscle mass in overweight to obese older adults. |
