The research was performed on 30 men and extended over a period of one and a half months. The men were classified as obese or overweight and compared results from two intervention groups (who ate breakfast before/after exercise) and a control group (who made no lifestyle changes), found that people who performed exercise before breakfast burned double the amount of fat than the group who exercised after breakfast.
The study established that increased fat use is mainly due to lower insulin levels during exercise when people have fasted overnight, which means that they can use more of the fat from their fat tissue and the fat within their muscles as a fuel.
While this did not show any significant weight loss, it has a very positive impact on their health because their bodies were better able to respond to insulin, keeping blood sugar levels under control and potentially lowering the risk of diabetes and heart disease. The researches also wanted to focus on the impact on the fat stores in muscles for individuals who either worked out before or after eating and the effect this had on insulin response to feeding.
In the trial that extended over a period of a month and a half, the research team found that the muscles from the group who exercised before breakfast were more responsive to insulin compared to the group who exercised after breakfast, in spite of identical training sessions and matched food intake.
The muscles from those who exercised before breakfast also showed greater increases in key proteins, specifically those involved in transporting glucose from the bloodstream to the muscles. For the insulin response to feeding after the six-week study, remarkably, the group who exercised after breakfast were in fact no better than the control group, the study said.