Study of vegetarian diets vs meat as protein source diets and muscle gain in older men (Effects of an omnivorous diet compared with a lactoovovegetarian diet on resistance-training-induced changes in body composition and skeletal muscle in older men).
Conclusions: Consumption of a meat-containing diet contributed to greater gains in fat-free mass and skeletal muscle mass with RT in older men than did an LOV diet.
Maximal strength of the upper- and lower-body muscle groups that were exercised during RT increased by 10-38% (P < 0.001), independent of diet. The RT-induced changes in whole-body composition and skeletal muscle size differed significantly between the mixed- and LOV-diet groups (time-by-group interactions, P < 0. 05). With RT, whole-body density, fat-free mass, and 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 muscle increased with RT for all men combined (P < 0.01), and the increase tended 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.
Another study showed favorable results for meat (Effect of protein source and quantity on protein metabolism in elderly women).
With the high-vegetable-protein diet, protein breakdown in the absorptive state was not inhibited to the same extent as during the high-animal-protein diet, resulting in less net protein synthesis during the high-vegetable-protein diet than during the high-animal-protein diet.