Fasting before exercising can assist with fat loss.
We have all tackled this question. I remember skipping breakfast before football practices. I was worried about getting sick in practice, but football practice was much more intense than my usual workout. My workouts today are much less intense, but the question remains, should you eat before a workout or fast?
I have seen many suggestions from so-called exercise experts. Some tell you to eat before, and others swear the answer is to eat after. I have even seen some recommend that it differs between men and women. Today, I found a new study that may shed some light on this topic.
The new study was published in the American Journal of Physiology — Endocrinology and Metabolism. The researchers exercised men in both a fasting and a non-fasting state for 60 minutes of walking. After completion of the exercise, the subject’s blood was tested for levels of gene expression levels 2 hours after exercise. The gene expression is an indicator of the level of fat storage and utilization. The testing indicated that fasting before exercise was tied to indications of more favorable levels of fat utilization.
I am not recommending that you not eat breakfast or skip it altogether. There is plenty of research that shows a link between successful weight loss maintenance and the habit of eating breakfast, but that link is not necessarily indicating causality. All that means is that people that tend to eat breakfast also tend to be more successful with their weight loss.
The bottom line: Fasting before exercise appears to be tied to better fat loss if the gene expression test is a good indicator. This concept makes sense if you understand physiology. Exercise tends to make people feel full and will likely reduce the amount of breakfast eaten, and you might burn more fat if you exercise on an empty stomach. The study is limited to men, but there is no indication that this is a male-only phenomenon. The problem with this study is that it does not indicate weight loss but measures gene expression that should be favorable changes for fat loss, but that being said, these results should indicate ideal conditions for fat loss. I recommend that you consider exercising on an empty stomach.
Chen, Yung-Chih, Rebecca L. Travers, Jean-Philippe Walhin, Javier T. Gonzalez, Francoise Koumanov, James A. Betts, and Dylan Thompson. “FEEDING INFLUENCES ADIPOSE TISSUE RESPONSES TO EXERCISE IN OVERWEIGHT MEN.” American Journal of Physiology – Endocrinology And Metabolism. American Physiological Society, March 14, 2017. doi: 10.1152/ajpendo.00006.2017