“It’s important to realize,” writes Lance Armstrong's coach Chris Carmichael in Food for Fitness, “that you burn carbohydrate, protein, and fat simultaneously whenever you exercise, regardless of the intensity of the workout.”
In fact, we need all of those elements in our diets at all times.
However, Carmichael and his co-authors go on to explain that during low-intensity workouts, most of our energy comes from fat – that’s fat from the food we’ve eaten and fat that’s been released from our body stores. We still need the carbohydrate, they reiterate, it’s just that at that level of energy output, we can efficiently burn fat to keep our muscles and brains going.
This is why Fodder and I lost weight in Paris: even though we wandered along the Boulevard St-Michel slowly, we did it for hours at a time and continually topped up with nutritious foods, so our little fat-burning engines could chug along until the last soprano sang.