In this article the author states that consuming carbohydrates is essential to athletes.
You store only carbohydrates -- not protein or fats - in your muscles in the form of sugar called glycogen. During hard exercise, you burn this glycogen for energy. When you deplete your glycogen stores, as can happen during repeated days of hard training and a low carbohydrate diet, you feel overwhelmingly exhausted. Eating high carbohydrate foods (cereal, pancakes, bread, fruit, vegetables, potato, pasta) on a daily basis can help you train harder and compete better.
If you are hungry, droopy and craving a quick energy boost prior to exercise, you don’t have to eat sugar for energy. A simple snack of crackers, fruit or bread can perk you up!
And finally the conclusion, where pizza is explicitly mentioned:
Remember that only carbohydrates quickly refuel your muscles and prepare you for tomorrow’s workout. So resist the greasy burger and fries for your post completion meal; choose instead carbohydrate rich thick crust pizza with cheese and veggie toppings or a baked potato with veggie toppings and a glass of fruit juice.
Although in the last paragraph the author talks about "tomorrow’s workout" it is obvious that she includes pizza among the carbohydrates an athlete could use and in the previous paragraphs she states that carbohydrates can "perk you up" prior to exercise.