Researchers at the National Institute of Aging, a division of the NIH, found that mice that consumed a standard diet but were fed every other day developed improved running endurance and were able to metabolize energy more efficiently. Their findings demonstrated how athletes can benefit from intermittent fasting.
The team of researchers, led by Mark P. Mattson, Ph.D., conducted the study by randomly assigning 35 male mice to four groups. Two of the groups were sedentary; one had regular access to food; and the other was fed every other day. Another group was provided with daily access to food, but assigned a treadmill. The final group had a treadmill and was fed every other day.
It was no surprise that at the end of the study the two groups with access to the treadmill had significantly better endurance on the treadmill, but researchers also found that the group deprived of food on alternating days could run faster and further than the group with unfettered access to both food and the treadmill.
At a glance, the four groups of mice still looked quite similar at the end of the study and had a similar body weight. Beneath the surface, the fasting group benefited greatly because their bodies were shifted into ketosis. This means that their bodies had switched from glucose to fats for their energy source. Researchers found superior gene expression in liver and muscle tissues in the mice that ate every other day. The fasting also improved their cellular energy by impacting their mitochondria, metabolic pathways, fatty acid metabolism and cell growth pathways.
The superior endurance of the mice in ketosis lays to rest the tired canard that athletes somehow benefit from loading up on carbohydrates. The common misperception that intermittent fasting and ketosis somehow hinder athletic performance has finally and firmly been debunked.
“Emerging evidence suggests that intermittent dietary energy restriction might improve overall health and reduce risk factors for diabetes and cardiovascular disease in humans,” Mattson says. “Our new findings in laboratory animals provide evidence that similar intermittent eating patterns can enhance the beneficial effects of aerobic exercise on endurance performance.”
This conclusion corresponds with previous research. Although the positive effects of intermittent fasting apply to everyone, athletes may benefit even more from limiting their eating to a defined window of time. A 2016 study that tracked the effects of time-restricted feeding (TRF) on 34 resistance-trained male athletes found restricting their eating to an eight-hour daily timeframe positively affected several health-related biomarkers, while decreasing fat mass and maintaining muscle mass.
One of my strongest cautions about intermittent fasting relates to food choices. Some claim that you can eat whatever you want as long as it is only consumed within your designated eating timeframe. While you may achieve some of the benefits from intermittent fasting simply by respecting the time boundaries, regardless of the foods you consume, I strongly recommend you consume high-quality food.
Whatever program you choose, your food choices matter. Since you’ll be eating less, it’s vitally important that you get proper nutrition from your food. Healthy fats are essential because intermittent fasting pushes your body to switch over to fat-burning mode. Particularly if you begin to feel tired and sluggish, it may be a sign that you need to increase the amount of healthy fat in your diet.