Time and again, fitness enthusiasts have a question–to exercise before or after breakfast. A new study published online in the American Journal of Physiology—Endocrinology and Metabolism has highlighted the role of fat toward metabolism. This is the first study that reveals the effects of fasting and feed status on human adipose tissue responses to exercise.
A research group from the University of Bath, UK, conducted a study on a group of obese males. Under fasting condition, the participants walked for 1 hour consuming a maximum of 60% oxygen, whereas in the fed condition, the walking duration increased to 2 hours after consuming a meal of 648± 115 kcal. At regular intervals, blood samples were collected in both fasting and fed conditions. The researchers also obtained adipose tissue samples at baseline and 1 hour after walking.
It was found that adipose tissue responded differently under fasting and fed trials. There was a rise in pyruvate dehydrogenase kinase isozyme 4 (PDK4) and hormone-sensitive lipase (HSL) with exercise in the fasted trials, and a decline with exercise in the fed trials. The increase in PDK4 indicates the probability of using stored fat for circulation during workouts rather than releasing carbohydrates from the meal. The corresponding author of the study, Dylan Thompson, explained that normally there would be a rise in HSL when adipose tissue uses the energy that is stored while supporting increased activity.
Thompson wrote that the study results supported the view that adipose tissue often faces competing challenges. In the fed conditions, adipose tissue is busy responding to the meal; and, exercise sessions at this time will not stimulate the same beneficial changes in the tissues. He concluded that fasting before carrying out exercise might provide positive changes in adipose tissue, benefitting health in the long term.