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Research Review: Skipping Carbs at Night Improves Endurance Performance & Metabolic Markers

Enhanced Endurance Performance by Periodization of Carbohydrate Intake: “Sleep Low” Strategy.

Marquet et al., 2016

    • Consistently high carbohydrate intake can reduce the bodies reliability on fat.
    • During endurance events and ultra endurance events a depletion of carbs can cause “bonking” and decreased performance.
    • “Training low” refers to periods of reduced carbohydrate intake around activities. This training method may help avoid “bonking” by reducing your reliance of carbs.
    • Results showed that triathletes who “trained low” by reducing carbohydrate intake at night had better performance and body composition changes than those on a regular diet.
    • This supports other research where you do the opposite and train fasted or with a low amount of carbs.
    • Specific periods of training where you reduce carb intake can promote positive training-induced adaptations in the skeletal muscle and may help improve athletic performance.
    • Selected workouts and important races / training sessions should still be performed with high carbs to maintain the bodies ability to utilize carbs for fuel and to optimize performance.


Over the last couple of years, a small number of endurance athletes are breaking away from the standard nutritional recommendations of a high carbohydrate diet, instead “training low” by restricting overall carbohydrate intake, or just at specific times.

The idea behind “training low” is that you are able to avoid the “bonking” during endurance events when you reach a state of fatigue due to nearly complete depletion of the stored carbohydrate in muscle.

However, research is mixed on whether on not athletes performance is improved using these strategies. Some literature suggests that training low often comes at the cost of performance gains, while others support the idea that exercise capacity may be improved by those who reduce their dependence on carbohydrates before and during especially prolonged exercise (Volek et al., 2015).

There is a need to better understand the level of carbohydrate restriction (and the overall composition of the diet) necessary to elicit these effects, as well as the factors contributing to variability between athletes.

The study took 21 highly trained triathletes and separated them into two groups, with the only difference between the two groups was the nutritional timing of carbohydrate ingestion. Overall carbohydrate was similar between groups.


Those who restricted their carbohydrates after an evening session found they had better exercise economy (e.g. more efficient at a set intensity), exercise capacity, and even improved their 10-kilometer running time during a low intensity morning session. They also decreased body fat by an average of 8 percent compared to the control group who only lost 2.5 percent.


Should I restrict carbohydrates at night?

The researchers concluded that the observed improvements were due to reducing carbohydrates before bed.

However, the observations in this study were not likely because of the widely held belief that “carbohydrates in the evening will make you fat.” In fact, multiple studies have shown this to be a false conclusion (Sofer et al., 2013; Sofer et al., 2014)

Rather, the most likely reason was because of the way the body can optimize its response to carbohydrate fuel utilization. In other words, the body learns how to use fuel stores in response to dietary intake and exercise need.

By “training low” in a reduced carbohydrate state, the body begins to make cellular adaptations that promote greater fat metabolism, and reliance on fat as a fuel (Volek et al., 2015). The longer that these adaptations are given to occur, the less likely that performance will be negatively impacted. In fact, it may have the potential to improve performance (Volek et al., 2015).

A key tenet in this strategy though is that you still provide high carbohydrate intakes during selected training sessions, so that your body still retains the function to optimally utilize carbohydrates during high intensity activities (Bartlett et al.,2015).

By doing so, you can promote a concept referred to as “metabolic flexibility”, or the ability to burn both carbohydrates and fats depending on the nutritional intake (Storlien et al., 2004).

Although the optimal practical strategies to train low are not optimized, consuming additional caffeine, protein, and practicing CHO mouth-rinsing before and/or during training may help to keep performance high, in addition to preventing protein breakdown and maintaining optimal immune function (Marquet et al, 2016; Pottier et al., 2010).


Periods of reduced carbohydrate intake are not necessarily a bad idea for training and body composition purposes, especially in the off season. When practiced in the right manner, performance can actually be improved and body composition changes can be superior to constantly flooding the body with carbohydrates.

If you want to implement this, dedicate a 4 week period and try fasting or skipping carbs at night following an evening training session. Remember, it’s best to do this in the off season as performance may decrease slightly as you adapt to this new strategy. However, over the long term it may help you drop 4 – 8 LBs and improve markers of performance.

If your looking to drastically improve performance and burn fat try these HIIT workouts that i’ve successfully used with elite athletes, World Triathlon Champions and Great Britain Age Group Triathletes:

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Bartlett, J. D., Hawley, J. A., & Morton, J. P. (2015). Carbohydrate availability and exercise training adaptation: Too much of a good thing?. European journal of sport science15(1), 3-12.

Marquet, L. A., Brisswalter, J., Louis, J., Tiollier, E., Burke, L. M., Hawley, J. A., & Hausswirth, C. (2016). Enhanced Endurance Performance by Periodization of CHO Intake:” Sleep Low” Strategy. Medicine and science in sports and exercise.

Sofer, S., Eliraz, A., Kaplan, S., Voet, H., Fink, G., Kima, T., & Madar, Z. (2011). Greater weight loss and hormonal changes after 6 months diet with carbohydrates eaten mostly at dinner. Obesity19(10), 2006-2014.

Sofer, S., Eliraz, A., Kaplan, S., Voet, H., Fink, G., Kima, T., & Madar, Z. (2013). Changes in daily leptin, ghrelin and adiponectin profiles following a diet with carbohydrates eaten at dinner in obese subjects. Nutrition, Metabolism and Cardiovascular Diseases23(8), 744-750.

Storlien, L., Oakes, N. D., & Kelley, D. E. (2004). Metabolic flexibility.Proceedings of the Nutrition Society63(02), 363-368.

Volek, J. S., Noakes, T., & Phinney, S. D. (2015). Rethinking fat as a fuel for endurance exercise. European journal of sport science15(1), 13-20.

About the author


Rudy Mawer, MSc, CISSN

Rudy has a 1st class BSc in Exercise, Nutrition & Health and a Masters in Exercise & Nutrition Science from the University of Tampa. Rudy currently works as a Human Performance Researcher, Sports Nutritionist and Physique Coach. Over 7 years he has helped over 500 people around the world achieve long last physique transformations.

He now works closely with a variety of professional athletes and teams, including the NBA, USA Athletics, World Triathlon Gold Medalists, Hollywood Celebrities and IFBB Pro Bodybuilders. If you would like to get in contact or work with Rudy please contact him on social media.

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