7 Ways Gut Microbiota May Impact Athletic Performance

7 Ways Gut Microbiota May Impact Athletic Performance

Your gut is home to over 100 trillion different microbes that play a synergistic role in your health and performance. The majority of your gut microbiota are made up of bacteria that reside in the colon, however viruses, fungi and protozoa also play key roles.(1) Scientists are still uncovering all the complexities of how these microbiota influence our health, although we do know they help to support vitamin production, the breakdown of fiber and communicate directly with your immune system.

The question for athletes is… “can your gut microbiota impact your athletic performance?” New research suggests it can. Let’s take a quick look at seven potential areas of interest:

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Can A Depleted-Glycogen “Sleep Low” Strategy Improve Your Performance?

The traditional nutrition dogma for athletes - in particular endurance athletes - has classically been to consume large amounts of carbohydrates pre- and post-exercise to optimize recovery and trigger maximal training adaptations. The sport nutrition research is very clear; muscle glycogen (the carbohydrate stores in your muscles) is replenished much more readily in the first few hours after training and higher carb (and protein) meals help to replenish glycogen and buffer training-induced increases in cortisol stress hormones.1,2

What did athletes do a few generations ago, before supplements and ready made food were so easily available? Did they ever not eat after exercise? And if so, did it derail their recovery and performance? Not likely. Interesting new research is uncovering how "timing" your carb intake and strategically avoiding replenishing glycogen may actually help improve your future performance (if done correctly).

What is the Sleep Low Strategy?

The "sleep low" strategy is defined as training intensely in the evening (after a typical meal) and then selectively withholding carbs in your subsequent meal after exercise (protein and fats are allowed) before going to bed. This strategy limits glycogen uptake after exercise, and thus your subsequent training session will be done with low glycogen stores, typically the following morning at low-intensity (e.g. light jog or easy lifts). 

For high performing athletes, the idea of purposefully not replenishing glycogen post-training seems to be a bad idea, as it's shown to be a major performance and recovery drain. However, a recent study in France of triathletes highlighted the potential benefits, if done acutely, of a sleep low strategy on performance.

Twenty-one triathletes were divided into two groups: a sleep low group and a control group. They ate the exact same total daily carbohydrates over the 3-weeks, but at different times throughout the day. The control group consumed their carbs across the entire day (i.e. breakfast, lunch and dinner) while the sleep low group consumed all of their carbs at breakfast and lunch, but nothing after their evening training, or before their morning session.

The researchers found after 3 weeks of doing the exact same training protocol, the sleep low group improved significantly more than the control in their submaximal cycling economy, supra-maximal cycling time to exhaustion and 10-km running time, and significantly decreased their fat mass.3

Don’t Cut the Carbohydrates Just Yet

If acutely restricting carbs helps performance, how far should you go? In today's "become a fat-burning machine" media coverage, should all endurance athletes be restricting carbohydrates to upgrade their performance?  

Like most things in life, context really matters. If you want to lose weight and exercise at 65% of your maximum effort, or take 6-18 months to adapt to a ketogenic diet, then a low-carb, high-fat diet is a pretty good approach. However, if winning a gold medal or beating elite competition is your goal then relying on fat for fuel is not going to cut it. (The exception might be "ultra" endurance events).

At high exercise intensities – like what you’d experience in a race – your body runs on about 90% carbohydrate. That’s right, when it’s time to hit the accelerator and pass your competition it won’t be the fats powering you, it will be the carbs. In fact, high-fat diets actually impair the muscles’ ability to breakdown glycogen, thereby limiting your access to the high-octane fuel.4

Individualize Your Plan To Supercharge Performance

Fortunately, it may be possible to get the best of both worlds, if your goal is performance. Use periodic three to four day blocks to “sleep low” and subsequently “train low” the following morning (i.e. low glycogen) to improve your fat-burning potential and ability to finish off a race.

But then avoid this approach when you get closer to competition and performance becomes critical. The research is still very clear that come race day, adding the carbs back in will allow you to perform better.

However, if your goal is to lose weight, boost your energy, and improve your health then the sleep low strategy could be very beneficial. I regularly see very active and experienced cyclists who ride hundreds of miles per week and are still 20-30 lb. overweight because of their very high-carbohydrate fueling.

Furthermore, this focus on fueling enough before, during and after exercise can lead to an excess of simple carbohydrates in the system and subsequent increases in triglycerides and smaller, denser LDL particles which all increase cardiovascular disease risk.5

A sleep low and train low strategy could be a game-changer for these athletes. Not only would it improve cycling performance, but it would also significantly reduce body-fat stores and improve health.

In truth, athletes have been tinkering with sleep low and train low strategies for decades, however now scientists are starting to get an understanding of how these strategies work and who they can potentially impact most. Think of “sleep low” and “train low” as just a few more tools in your tool belt of training strategies. Plan and periodize their use to maximize their benefits and limit their potential shortcomings.

Dr. Marc Bubbs ND, CISSN, CSCS



[1] Ivy J et al. Glycogen resynthesize after exercise: effect of carbohydrate intake. Int J Sports Med. 1998 Jun; 19 Suppl 2():S142-5.

[2] Tipton K et al. Timing of amino acid-carobhydrate ingestion alters anabolic response of muscle to resistance training. Am J Physiol Endocrinol Metab. 2001 Aug; 281(2):E197-206.

[3] Marquet L et al. Enhanced Endurance Performance by Periodization of Carbohydrate Intake: “Sleep Low” Strategy. Med Sci Sports Exerc. 2016 Apr;48(4):663-72.

[4] Stellingwerth, T et al. Decreased PDH activation and glycogenolysis during exercise following fat adaptation with carbohydrate restoration. Am J Physiol Endocrinol Metab. 2006 Feb;290(2):E380-8.

[5] Sachdeva A. Lipid levels in patients hospitalized with coronary artery disease: An analysis of 136,905 hospitalizations in Get With The Guidelines. American Heart Journal. January 2009. Volume 157, Issue 1, Pages 111–117.e2