Eating before physical activity or doing it on an empty stomach? What is better for health and to counteract abdominal fat? Well, it seems that physical activity, such as a brisk walk, on an empty stomach has greater benefits, especially in the long term, as emerges from a scientific research published a few years ago in the American Journal of Physiology - Endocrinology and Metabolism by an English team (Chen et al, Am J Physiol Endocrinol Metab, 2017).
The danger of visceral fat
Adipose tissue, especially if located around the waistline, is not inert but can cause resistance to insulin and produces hormones and substances capable of raising inflammation levels.
The benefits of physical exercise
Exercise requires energy and this is provided by adipose tissue through the mobilization of accumulated triglycerides. Not only that, exercise improves blood flow and counteracts the release of pro-inflammatory substances from adipose tissues. This is why physical exercise is so beneficial to counteract the famous pot belly but also for the well-being of the entire body. However, little is known about how the body's response to exercise can vary in conditions of fasting or after eating. In other words, is physical exercise always equally beneficial regardless having an empty stomach or after eating? To try to answer this question, British researchers from the University of Bath have developed an experiment, which we are talking about today.
Physical activity on a full or empty stomach, the experiment
The researchers recruited ten young adults, aged between 18 and 35, all with abdominal fat. At first, volunteers were asked to walk briskly for an hour on an empty stomach. Later, the experiment was repeated but two hours later a breakfast rich in carbohydrates given by bread, jam, cornflakes, milk and sugar. Before, during and after the walk, blood and adipose tissue samples were taken in order to understand any changes and the body's responses to exercise.
Fasting is more beneficial against body fat
What emerged is that doing moderate physical activity after eating could mitigate, in the long run, some benefits given by the same physical activity, carried out on an empty stomach. In fact, walking on an empty stomach promotes the use of stored fat for energy, thus improving metabolism and counteracting the accumulation of fat. Walking after eating, on the other hand, changes the response of fat, which seems to adapt more to physical exercise. In fact, the researchers observed that walking after eating leads to a decrease in certain enzymes, such as PDK4, ATGL and HSL. PDK4 regulates glucose metabolism and its increase is linked to weight loss and a decrease in body fat while HSL and ATGL are designed to move accumulated triglycerides to burn fat stores and produce energy. However, like any activity, also walking after eating has the advantage to keep under control the dangerous blood sugar spikes.
Warnings and conclusions
The article does not want to state that to stay fit and healthy you must not eat. What emerges simply indicates that, for those who are overweight and especially have visceral fat, greater benefits can be obtained, in the long term, with a moderate intensity walk on an empty stomach. Physical activity, whether fasting or after eating, is still a healthy choice, also to keep blood sugar and chronic inflammation under control.