Effects of an omnivorous diet compared with a lactoovovegetarian diet on resistance-training-induced changes in body composition and skeletal muscle in older men

Background: Very limited data suggest that meat consumption by older people may promote skeletal muscle hypertrophy in response to resistance training (RT). Objective: The objective of this study was to assess whether the consumptio n of an omnivorous (meat-containing) diet would influence RT-induced change s in whole-body composition and skeletal muscle size in older men compared with a lactoovovegetarian (LOV) (meat-free) diet. Design: Nineteen men aged 51-69 y participated in the study. During a 12-wk period of RT, 9 men consumed their habitual omnivorous diets, which provid ed approximate to 50% of total dietary protein from meat sources (beef. pou ltry, pork, and fish) (mixed-diet group). Another 10 men were counseled to self-select an LOV diet (LOV-diet group). Results: Maximal strength of the upper- and lower-body muscle groups that w ere exercised during RT increased by 10-38% (P < 0.001), independent of die t. The RT-induced changes in whole-body composition and skeletal muscle siz e differed significantly between the mixed- and LOV-diet groups (time-by-gr oup interactions, P < 0.05). With RT, whole-body density, fat-free mass, an d whole-body muscle mass increased in the mixed diet group but decreased in the LOV- diet group. Type II muscle fiber area of the vastus lateralis mus cle increased with RT for all men combined (P < 0.01), and the increase ten ded to be greater in the mixed-diet group (16.2 +/- 4.4 %) than in the LOV diet group (7.3 +/- 5.1%). Type I fiber area was unchanged with RT in both diet groups. Conclusion: Consumption of a meat-containing diet contributed to greater ga ins in fat-free mass and skeletal muscle mass with RT in older men than did an LOV diet.