Exercise and fasting: Is it all cons?

Physical activity offers many long-term benefits to people’s physical and mental well-being. However, personal nutritional conditions may need to be met in order to make exercise effective and healthy. With these conditions in mind, is it advantageous to exercise while fasting?

Due to busy lifestyles and constant demands, many Americans minimize their intake of food and drink prior to exercising in the morning. According to Samuel L. Buckner and others in the American Journal of Clinical Nutrition, “Nearly one-quarter of individuals in the United States skip breakfast daily, with an average energy contribution of ~16% of total caloric intake.” This is opposed to the contribution from dinner that provides ~44% of daily caloric intake, Buckner and others explained. 

Despite the lack of calories that comes as a result of skipping breakfast, does avoiding the first meal of the day have proven negative effects on health? 

The question is hotly contested. According to health reporter Markham Heid of Time Magazine, while it may be true that exercising on an empty stomach can increase the effectiveness of a post-workout fat burn through increased metabolism, it may also bring negative effects due to low blood sugar such as sudden loss of energy, increased difficulty in continuing exercise, immediate dizziness, and other, more serious side effects. 

Regarding the widespread taboo of fasting while exercising, UVU student Alexandra Ramirez, studying business management, said, “I have heard of popular wisdom that exercising on an empty stomach is a great option since this way the body pulls accumulated fat to use as fuel. I don’t know if it is true, but that’s what many friends say.”

This example is why it is important to take into account the state of each individual’s health when advising for or against exercising on an empty stomach. If a person has just started exercising, they should gradually increase exercise intensity to the point where they may consider exercising while fasting instead of increasing exercise intensity at an unhealthy rate and on an empty stomach. 

Despite these considerations, doctor Tamar Kessel and others in The Aging in Motion (AIM) Coalition claim that it is possible to find the following advantages through fasting and exercising:

• Improved muscle quality, since special muscle fibers are generated which contain large amounts of mitochondria.

• Quicker recovery, since increased metabolism creates lower levels of lactic acid and provides for an easier elimination process.

• Improved aerobic muscle performance, since tissues are better oxygenated.

• Better metabolism of fats, through the increased removal of amino acids and fats so that muscles may have more available energy. 

As stated, there are many reported advantages of combining exercise and fasting. However, according to an article published by U of T News, dietitian Eric Williamson recommends that intermittent fasting should be done in conjunction with exercise, particularly resistance training. The reason for this is that when people practice intermittent fasting without exercising, they tend to lose weight through lean muscle mass atrophy, whereas if they exercise concurrently with fasting, the weight loss shifts from muscle mass loss to fat mass loss.

The decision of whether or not to fast during exercise is a personal choice and may need to be made with the advice of medical professionals. Although it is acceptable to exercise on an empty stomach, it is recommended for light or moderate activities. However, to perform more intense exercises that lead to a significant calorie deficit, a meal or other food should be consumed to provide the necessary energy.