Diet and exercise, diet and exercise, diet and exercise. Like love and marriage, the two seem to go together like a horse and carriage. And for good reason: what you eat and how much you move exert a synergistic effect to favorably impact your health.
But what is the influence of one on the other. In other words, does diet impact your fitness level and exercise performance? We know that exercise increases your caloric expenditure and can cause you to consume more food, which is fine provided it is of the nutrient-rich variety. If too often you reward yourself after a 3-mile jog with a large muffin of the coffee-shop variety, you can wind up adding to your fat stores rather than trimming down, since muffins, bagels, and other calorie bombs can easily contain twice the calories you're trying to replenish (muffin: 600 calories; 3-mile jog: 300). The resultant net gain you wind up wearing around your waist, hips, face, or thighs.
But joking aside, does a healthy diet, in and of itself, improve your physical fitness? Yes, says Amy Donaldson, a young mother who by adopting a plant-based approach knocked nearly a half an hour off her half-marathon time, running a personal best 2:21. What's most impressive about this feat is that Amy did not alter her training. All she did was modify the foods she ate, choosing fruits and vegetables over meat and dairy. Go Amy!
Now, while we love anecdotal evidence, we want to know: What does the literature say? Early studies point to a tremendous increase in endurance performance associated with a high carbohydrate diet, quadruple what was seen in a high fat, high protein diet. It was from these studies that the concept of carb loading derived.
According to an article on vegetarian diet and endurance performance published in the American Journal of Clinical Nutrition, endurance athletes (runners, bikers, swimmers, and the like) are urged to consume a diet of 70% carbohydrate in order to maximize muscle glycogen stores and guard against fatigue. And deemphasizing animal foods (which have no carbohydrate) in favor of carb-rich fruits, vegetables, and beans makes it easy to meet the carb target and maximize performance. The article also notes the cardioprotective quality inherent in plant-based foods. In addition, the antioxidants present in plant foods (vitamins like A, C, and E) protect against the oxidative stress of exercise. These antioxidants are present almost exclusively in fruits and vegetables.
So in the race called life, carbs seem to be the fuel of choice, and the best sources bar none are plants.