Vegetarian diets have been associated with lower death rates from heart disease and decreased risk of obesity, and you can choose to be a vegetarian without having your athletic performance suffer. A 2012 study published in the "Journal of the International Society of Sports Nutrition" looked at bicyclists who followed either a vegetarian or meat-containing diet. While the vegetarian group had slightly lower oxygen levels during submaximal effort, results did not demonstrate that a vegetarian diet decreases exercise potential. A 2011 study published in the "European Journal of Applied Physiology" confirmed these results. Athletes performing sprint training followed a vegetarian or mixed diet, and both groups saw the same improvements in athletic performance. If you're concerned about decreased athletic ability, research indicates that a vegetarian diet does not negatively affect your exercise performance, but has the same result as following a meat-containing diet.