On the recent BBC program "The Truth About Food" they looked at this issue, using a group of eleven female vegetarian amateur martial artists as test subjects. They persuaded six of them to start eating meat again, twice a day, for eight weeks, while the other five continued eating vegetarian protein sources.
Unfortunately, the results were inconclusive, although the meat eating group were able to run for 9% longer. At the same time, the Olympic hurdler Colin Jackson became a vegetarian for eight weeks to see if it effected his performance.
After 8 weeks, Jackson was able to do five less push ups, and anecdotally, felt that his muscle tone had reduced.
Until there are larger, more long-term studies, we won't know for sure if there are any differences between vegetarians and meat eaters, but it's worth noting that successful vegetarian bodybuilders tend to use the following strategies:
- They eat chicken and fish
- They use a lot of concentrated protein supplements
Of course, what you eat is a personal decision, but if you are looking to build muscle or achieve sporting success, you have to balance out the pros and cons of vegetarianism.