People who exercise often wonder whether it is better to eat or not before a workout. A new study is the first of its kind to show the effects of eating versus fasting on gene expression in (fat) tissue in response to exercise. This study highlights the different roles fat plays in feeding and responding to exercise.
Researchers studied a group of overweight men. The volunteers walked for 60 minutes at 60 percent maximal oxygen uptake on an empty stomach and, on another occasion, two hours after consuming a high-calorie, carbohydrate-rich breakfast. The research team took several blood samples after eating or fasting and after exercising. The researchers also collected adipose tissue samples immediately before and one hour after exercise.
Gene expression in the adipose tissue differed significantly in the two studies. Expression of two genes, PDK4 and HSL, was increased when the men fasted and exercised and decreased when they ate before exercise. The rise in PDK4 indicates that stored fat was likely used to fuel the metabolism during exercise rather than carbohydrates from the recent meal. HSL usually increases when adipose tissue uses stored energy during increased activity, such as during exercise.
These results reinforce the view that adipose tissue often faces conflicting interests, the researcher said. After eating, the adipose tissue is responding to the meal and a bout of exercise at this point will not stimulate the same [positive] changes in the adipose tissue. This means that training in a fasted state can elicit more beneficial changes on the adipose tissue, and this would be beneficial for long-term health.
