A study released in The Journal of Clinical Endocrinology and Metabolism found that when men exercise before eating breakfast they burn twice as much fat as men who exercised after eating breakfast. Although the fat loss didn’t always result in weight loss, the team believes that pre-breakfast workouts have a significant effect on “key aspects of metabolic health” particularly in men who are obese.
Arguably the most important of these “key aspects” was a marked reduction in the overproduction of insulin, a hormone that is essential in the body’s ability to digest sugar and store it for energy later on. It is well known that obesity causes the body to overproduce insulin, and that the overproduction in insulin is linked to further obesity and health complications over time (Type 2 Diabetes).
The study found that men who exercised before eating breakfast used twice as much fat for energy as men who exercised after eating breakfast, who used fat and carbohydrates for their energy. Essentially, the researchers believe that the reason behind the increased fat burn comes down to the effects on the body of fasting overnight, and that these effects are surprising similar to the effects of intermittent fasting.