The eat-first camp says food before exercise boosts blood sugars, giving the body fuel to increase the intensity and length of a workout.
A small UK study published Friday supports the latter point of view: In 30 obese or overweight men, those who exercised before breakfast burned twice the fat as men who ate breakfast before they worked out.
That's because exercising with no fuel forces the body to turn to stored carbs, and when those are quickly gone, to fat cells.
However, this time the men burned more calories if they ate breakfast first.
But contrary to the 2017 study the group who ate breakfast before exercise also gained weight.