We’ve been hearing for years that cardio done in a fasted state — first thing in the morning, on an empty stomach — burns fat at a higher rate than in a “fed” state. Fasted cardio was all the rage a decade ago, and then fell out of fashion for a while, and now it seems that a study confirms that at least for some men, fat metabolism is boosted by some 20 percent if they crank it out on the treadmill before they eat breakfast.
Bear in mind that this study was conducted on a small group — 12 physically active men.
The men did a treadmill workout at 10 a.m., either after they had eaten breakfast or without eating since the night before. After the workout, they were given a chocolate milkshake recovery drink. Later, they were provided a pasta lunch and were told to eat until they felt comfortable full. Researchers then assessed their consumption of energy and fat, including the amount of energy and fat burned during exercise.
Not only did the fasted group burn 20 percent more fat during exercise, they didn’t eat any extra calories to make up the shortfall — and they didn’t experience increased appetite.
So it seems there’s more evidence that fasted cardio can give a boost toward fat loss. However, here’s a catch: some studies show that women can experience increased appetite as a result of exercise and can subconsciously eat extra calories without realizing it, which offsets any weight loss they might experience.
My practical non-laboratory/real-world takeaway? If you like to do your cardio in fasted state first thing in the morning, go for it! But if fat (or weight) loss is a goal, still be aware of your calorie intake because unless you create a calorie deficit, that scale isn’t going to budge.