A study published in the American Journal of Physiology by researchers at the University of Bath found you might be likely to burn more fat if you have not eaten first.
Their blood samples were taken after eating or fasting and then after exercising. Gene expression in fat (adipose) tissue differed significantly in each scenario and the expression of two genes increased when the men fasted and exercised and decreased when exercising after eating. This likely signals that stored fat was used to fuel metabolism during exercise rather than the carbohydrates from the meal.
After eating, the fat tissue is “busy responding to the meal and a bout of exercise at this time will not stimulate the same [beneficial] changes in adipose tissue. This means that exercise in a fasted state might provoke more favourable changes in adipose tissue and this could be beneficial for health in the long term,” author of the study Dylan Thompson wrote.
Adipose tissue plays an important role during exercise and during moderate exercise provides much of the energy for working skeletal muscle
Mr Thompson said that as adipose tissue is impacted by weight loss and weight gain (the genes increase in weight loss and decrease in weight gain) their research proposes “feeding before exercise blunts some of the health-related changes induced by exercise training”.
However, the study does have limitations in the fact only ten men were measured and it only measured the effects of skipping breakfast on a morning workout, not other mealtimes. The study also does not mean that skipping a meal before exercising will result in accelerated weight loss.
Ruben Tabaras, a personal trainer and strength and conditioning coach, recently told The Independent he personally does not eat before a workout as it makes him feel unwell.
“If the stomach is digesting food then it is using bloody to do so and that blood could better be used in the muscles, hence why people feel sick when working out,” he suggested.
However, many athletes and other personal trainers ensure they eat something carb and protein heavy in order to have the correct amount of fuel in their body to power them through a tough workout.
