How Fasting Boots Exercise’s Effects on Endurance

Intermittent fasting, such as eating only on alternate days, might enhance the ability of aerobic exercise to increase endurance because the body switches to using fats and ketones as a source of fuel for muscles instead of carbohydrates.

This was the conclusion that researchers came to after studying the effect in mice with such a regimen for a limited period of time. Their study is to be published in the FASEB Journal.

The findings suggest that three meals per day and snacking may not be the only eating habit for people who engage in endurance sports to reach peak performance and maintain good health.

“Emerging evidence,” explains senior study author Dr. Mark Mattson, from the Laboratory of Neurosciences in the National Institute on Aging in Baltimore, MD, “suggests that [intermittent dietary energy restriction] might improve overall health and reduce risk factors for diabetes and cardiovascular disease in humans.”

He and his team say that their findings propose that a similar pattern of eating and fasting may boost the beneficial effect of moderate aerobic exercise on endurance, and that it should be studied further.

For the study, the team put mice into four groups and observed them for 2 months as they went through the following exercise and eating patterns:

The control (CTRL) mice did not exercise at all and could eat as much food as they wanted every day.

The exercise (EX) mice could eat as much daily food as they wanted, but they also ran on a treadmill for 45 minutes each day.

The “alternate day food deprivation: (ADF) mice were only fed a fixed amount on every other day and did not exercise at all.

The EXADF mice were restricted to the ADF eating pattern but also exercised every day on a treadmill for 45 minutes.



As expected, the results showed that the mice that exercised daily performed better in the endurance tests that the groups that did not exercise. However, the EXADF mice had better endurance that the daily exercise mice that were allowed to eat what they wanted (EX group).

The researchers also found that the mice on ADF were able to maintain their body weight and had better glucose tolerance, “regardless of whether they exercised or not.” They note that, following glucose metabolism, although the EX group’s glucose levels recovered at a faster rate than the CTRL group’s, the glucose levels of the ADF and EXAF groups recovered even faster.

My Take:
The pattern of intermittent fasting “reminds us of the nexus between our own hunter-gatherer metabolism, still operative, and modern habits, with the findings from this animal system likely transferable to us to a considerable degree.”

I have not observed patients adopting this eating pattern, but I have some colleagues who have experimented with it personally with good results. I plan on experimenting with ADF myself and with a select group of patients in the near future.

The Bottom Line:
If you are struggling with weight loss despite dietary restrictions and regular exercise, try intermittent fasting. I think every other day is too frequent. I’d recommend two days of eating then one day of fasting.

Source: National Institutes of Health February 27, 2018