Intermittent fasting (IF) is trending in the fitness space. Even those outside the fitness world have probably heard of IF and you may be curious about its effects on you and especially your athletic performance. The craze is big and if it suits your lifestyle, IF could be both good for your health and, if used correctly, good for your athletic performance.

What is Intermittent Fasting?

Intermittent fasting is simply the concept of eat-stop-eat. There is a period of prolonged time without food. Most fasting protocols involve 16 hours or more without food each day. There are purported health benefits, such as loss of body weight, mental clarity, improved insulin sensitivity, and autophagy (clearing of damaged cells in the body). Various fasting regimens may suit you better, such as 16:8 (fasting:eating), 20:4, or 22:2.

Fasting and Exercise

An article which reviewed the effect of IF on athletes during Ramadan found that there are little to no negative effects of IF on exercise performance in endurance training (running, cycling, etc.) or resistance training (lifting weights). There was also no clear athletic benefit to IF, though the authors stated that only short-term fasts were studied. Longer term adaptation to IF may produce different results, so your own testing of your body is important.

Another review article found that IF is effective for reduction of fat mass, improving body composition. The study did find a slight reduction in VO2 max, a marker of intense exercise capacity. VO2 max is the oxygen consumption during exercise, an important measure of capacity. Athletes considering IF as their dietary regimen should consider what benefit they wish to gain. A possible slight reduction in performance may be insignificant if your goal is to get leaner while someone chasing peak performance may find better benefit from a non-fasting diet.

Conclusion

Intermittent fasting does not appear to produce athletic benefits. The literature shows a general consensus on no negative effect of fasting regimens. The most important thing to consider when choosing a diet is what you can sustain. Dietary changes are not meant to be short-term: we should aiming for what we can do for life. If intermittent fasting is something you’re interested in, give it a shot (after consulting a doctor) and see what benefits you may gain.

References

Correia, J. (2020). Effects Of Intermittent Fasting On Exercise Performance And Body Composition: A Systematic Review And Meta-analysis. Medicine & Science In Sports & Exercise, 52(7S), 456-456. https://doi.org/10.1249/01.mss.0000678884.52960.d2

Levy, E., & Chu, T. (2019). Intermittent Fasting and Its Effects on Athletic Performance. Current Sports Medicine Reports, 18(7), 266-269. https://doi.org/10.1249/jsr.0000000000000614

Calling all herbivores! There is nothing to fear in the athletic department. Those with a passion for exercise but also interested in a vegan diet may be nervous that their performance will suffer after the switch. Eating how you want to eat and performing how you hope to is possible, if you are smart about how you structure your diet.

What is a Vegan Diet?

The vegan diet is one free of all animal products. This means all meat, fish, eggs, dairy, honey, and some other niche items are off the table. People may choose to go vegan for health reasons, ethical reasons, or even a love of the food! A healthy vegan diet includes a wide variety of fruit, vegetables, grains, nuts, and seeds. Whatever your reason is, you can still pursue any physical goals you have while eating the foods want.

Exercise Capacity

You may be worried about the idea of your diet putting you at risk of falling off your performance goals, or even getting worse! Rest easy, the science says otherwise. A study of recreational runners with similar training but different diets (vegan, lacto-ovo-vegetarian, and omnivorous) were compared on an exercise capacity test [1]. All three groups has similar power output and maximal capacity, meaning no diet was superior than another for exercise capability. If your food is clean and enough for you, there is no reason you can’t achieve your goals.

Doing Vegan Right for Exercise

Vegans may run the risk of missing some important nutrients in their diets. A comprehensive narrative review showed that vegans should be aware of possible deficiency in protein, fat, vitamin B12, Riboflavin, vitamin D, calcium, iron and zinc [2]. Getting a diversity of nutrient in your diet is important to maintaining optimal performance. Research foods that have these nutrients, like nuts for protein and fat and dark greens for iron, to ensure you are eating enough. It is a great idea to consult a doctor to have a test done for vitamin deficiency. That way you can ensure you add in foods that cover your nutrition holes and keep you feeling your best!

Whatever your reason for considering a vegan diet, go for it! You can have your vegan cake and eat it too, no worries. Eating the right variety of foods and eating enough to support your life demands will have you performing how you want in and out of the gym.

References

[1] Nebl, J., Haufe, S., Eigendorf, J., Wasserfurth, P., Tegtbur, U., & Hahn, A. (2019). Exercise capacity of vegan, lacto-ovo-vegetarian and omnivorous recreational runners. Journal Of The International Society Of Sports Nutrition, 16(1). https://doi.org/10.1186/s12970-019-0289-4

[2] Rogerson, D. (2017). Vegan diets: practical advice for athletes and exercisers. Journal Of The International Society Of Sports Nutrition, 14(1). https://doi.org/10.1186/s12970-017-0192-9