Intermittent fasting may enhance endurance when combined with moderate aerobic exercise

28 Feb 2018 --- Intermittent food deprivation paired with moderate aerobic exercise may enhance endurance, according to a study conducted on mice. The new study, published online in The FASEB Journal, suggests an alternative to eating three meals a day plus snacks for optimal health and maximum performance in endurance sports.

The study showed that intermittent dietary energy restriction (IER) during one month of daily moderate aerobic exercise training enhanced endurance performance. These findings suggest that intermittent periods of food deprivation, which shift the muscle fuel source from carbohydrates to fats and ketones, should be further examined for their effectiveness in improving endurance.

“Emerging evidence suggests that IER might improve overall health and reduce risk factors for diabetes and cardiovascular disease in humans,” says Mark Mattson, Ph.D., Senior Investigator, Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health.

“Our new findings in laboratory animals provide evidence that similar intermittent eating patterns can enhance the beneficial effects of aerobic exercise on endurance performance," Mattson says.

The researchers observed four groups of mice for two months. One group remained sedentary and had food available to eat 24/7. The second group ran for 45 minutes on a treadmill every day and was also fed ad libitum. The third group remained sedentary and was deprived of food for 24 hours every other day. The fourth group ran for 45 minutes every day while maintaining the alternate day food deprivation regimen.

Unsurprisingly perhaps, the mice that ran on the treadmill daily had better endurance than the sedentary mice. However, the mice on IER during the treadmill training were able to run farther and longer than the mice on the ad libitum diet during the treadmill training.

Intermittent fasting becomes increasingly popular
With rates of obesity continuing to skyrocket, the weight loss market is seeing persistent growth, and Intermittent fasting (IF) is one of the dietary patterns seeing increasing popularity. 

IF is an umbrella term encompassing a range of diets where the pattern of calorie restriction and timing of food intake are altered so that individuals undergo frequently repeated periods of fasting or modified fasting (allowing a low-calorie intake of approximately 500-600 calories per day). 

In general, most science-based diets build in a form of calorie-restriction and/or focus on macronutrient distribution. “The latest diets and trends that are growing quickly are based upon variations of Intermittent Fasting (IF),” says Dr. Rona Antoni, Registered Dietitian and Research Fellow in Nutrition Metabolism at the University of Surrey.

“These are highly popular today. Proponents of IF claim that it can improve blood sugar levels, decrease the risk of heart disease, stroke and cancer, prevent or delay the onset of neurodegenerative diseases and even improve memory, mood and depression,” adds Dr. Roy McGroarty, an Infectious Disease Specialist and Humanitarian relief, recovery and development Program Manager. 

Popular examples of diets based on IF include the 5:2 diet and alternate day fasting. In May, Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) launched a new “flexi” diet that includes intermittent fasting three days a week. The weight loss program is based on research carried out by CSIRO scientists who found that fasting can be an effective way to lose weight and stay healthy.

The reason that fasting can have a positive effect on harmful processes in the body is that during all kinds of fasting periods, various biochemical and molecular changes take place in the body. These include an increase in certain protective proteins, antioxidant enzymes, vitamin E and coenzyme Q10; all of which have a protective effect and prevent inflammation and oxidative stress.

“The idea behind the IF diet is threefold: The first is glycogen depletion as a result of fasting,” explains Dr. Samefko Ludidi, a food researcher at the Gastronomy Research Center of the Hotel Management School Maastricht. “Depending on your level of physical activity glycogen stores are depleted after a period of about 8-12 hours fast. Second, following glycogen depletion, the body starts utilizing fat stores as an energy source. Third, fasting results in an average energy deficiency compared to the normal situation. The combination of these three aspects could result in weight loss.”

One drawback of IF is that the initial transition is quite difficult. How difficult depends on the individual, as the body only requires one to two weeks to adjust to the new eating schedule. 

Some argue that you could eat anything when on an IF diet, as long as you stay in the negative energy balance. “But it is not only about calories. You cannot expect to lose weight healthily by getting that energy deficit from drinking a bottle of soda each day,” stresses Ludidi. 

McGroarty adds: “The food industry can, therefore, help by lowering the production of highly processed foods, agreeing to better nutrition labeling and by stopping the ‘Bliss Point’ food testing method. In almost every case it involves adding sugar far beyond what the body requires.” Antoni concludes: “The modern-day food environment makes sustainable, healthy eating behaviors difficult. The industry has the responsibility to do their bit and make it easier for the consumers.”

For a detailed article on intermittent fasting by Maartje Geraedts, see “Intermittent Fasting: A New Year's Resolution” in the February issue of The World of Food Ingredients.

By Lucy Gunn