How Does Nutrition Affect Exercise? The nutrients you consume can affect the quality of your exercise. The muscles you engage during exercise, whether itâs cardio, resistance training or flexibility work, rely on the nutrition you provide them through your diet. Supplying your body with nutrients before you work out, after you work out and in the recovery period between workouts can impact the quality of your session and affect your fitness goals. In some cases, fueling up during an exercise session can improve your results as well.