Going on a low carb diet means reducing carbs, and on the ketogenic diet, which is a low carb, high-fat diet that typically means eating around 30-50 grams of carbs a day (which varies per person). For people who are considering going on the ketogenic diet, a common concern is what type of exercise is best to implement. First off, exercise is very acceptable on the keto diet and has many health benefits — which we discuss in the Body Reboot book. Beyond that though, many wonder if exercise will impact their performance (since a body typically burns carbs to perform adequately), or if eating fat will suffice. The good news is a body not only can go without carbs during a workout (even though some experts would disagree), studies show that being on a keto diet AND exercising can accelerate weight loss. Do you want to know why that’s the case? Keep reading:

Perfect Keto argues that being in ketosis (which is a process where your body burns fat instead of glucose), is not hinder your long-term exercise goals and that in fact, a recent study showed that people who exercise burned 2-3 more fat. Whether you’re trying to lose weight or not, being on the keto diet and exercising has many benefits.

It might seem like ketosis is a hindrance to long-term exercise, but it actually has shown to provide significant benefits:

In one recent study, during a three-hour-long run, 2-3 times more fat burn was seen in ultra-endurance athletes who ate low-carb for an average of 20 months versus those following a high-carb diet.

In the same study, the low-carb group used and replenished the same amount of muscle glycogen as the high-carb group.

Being in ketosis might also help prevent fatigue during longer periods of aerobic exercise.

Plus, ketosis has been shown to help with blood glucose maintenance during exercise in obese individuals.

As mentioned above, the power of keto-adaptation helps low-carb dieters perform better in all forms of exercise with less carbs over time.

The Metabolism study from March 2016 found that a ketogenic diet does not affect an athlete’s performance and that it has many benefits such as a person feeling more energetic from burning fat.

BACKGROUND:

Many successful ultra-endurance athletes have switched from a high-carbohydrate to a low-carbohydrate diet, but they have not previously been studied to determine the extent of metabolic adaptations.

METHODS:

Twenty elite ultra-marathoners and ironman distance triathletes performed a maximal graded exercise test and a 180 min submaximal run at 64% VO2max on a treadmill to determine metabolic responses. One group habitually consumed a traditional high-carbohydrate (HC: n=10, %carbohydrate:protein:fat=59:14:25) diet, and the other a low-carbohydrate (LC; n=10, 10:19:70) diet for an average of 20 months (range 9 to 36 months).

RESULTS:

Peak fat oxidation was 2.3-fold higher in the LC group (1.54±0.18 vs 0.67±0.14 g/min; P=0.000) and it occurred at a higher percentage of VO2max (70.3±6.3 vs 54.9±7.8%; P=0.000). Mean fat oxidation during submaximal exercise was 59% higher in the LC group (1.21±0.02 vs 0.76±0.11 g/min; P=0.000) corresponding to a greater relative contribution of fat (88±2 vs 56±8%; P=0.000). Despite these marked differences in fuel use between LC and HC athletes, there were no significant differences in resting muscle glycogen and the level of depletion after 180 min of running (-64% from pre-exercise) and 120 min of recovery (-36% from pre-exercise).

CONCLUSION:

Compared to highly trained ultra-endurance athletes consuming an HC diet, long-term keto-adaptation results in extraordinarily high rates of fat oxidation, whereas muscle glycogen utilization and repletion patterns during and after a 3 hour run are similar.

Burning fat has its benefits, which is why Ketovangelist also argues that when your body needs to burn something to survive and doesn’t have sugar, it will automatically burn fat. If you guessed why exercise helps with that, then you guessed correctly.

You deplete glycogen quickly

As long as your body has sugar to burn, it will burn it. Only by removing the sugar will you force your body to burn fat, that includes the stored sugar you have in your muscles. Your body wants to stay alive, so it does things to make sure of that result. One of those things is storing sugar in the form of glycogen, which is, essentially just glucose (sugar) molecules that have been strung together to form a bigger molecule. Glycogen exists in two places, your liver and your muscles. Glycogen that enters your liver can exit your liver and be used wherever your body needs it. Glycogen that enters your muscles cannot leave. So it it must be used by the muscles. And your muscles will use that glycogen for energy as long as it’s there. HIIT makes those glycogen deposits burn away. Fast. So you become a fat burning machine (especially if you eat high fat and moderate protein after you work out). The harder you work, the faster you burn through your glycogen.

Forever Fit Science adds to the sources we mentioned above by stating that a study in the Czech Republic talked about HIIT exercise in particular and the researchers also found that activity was not affected by being on a low carb diet.

Research out of the Czech Republic aimed to determine whether the keto diet offers a sufficient energy source for athletes and if it has any effect on the physiological variables during high-intensity interval training (Cipryan et al, 2018). They compare the effects of shifting from a habitual mixed Western diet to the keto diet on the physiological responses to a graded exercise test and a HIIT session. Since aerobic and anaerobic exercise performance has previously been found to be highly reliant on the availability of carbohydrates in the body, do limited carbohydrates affect athletic training and performance?

This study was comprised of eighteen moderately trained males between the ages of 18 and 30, who were divided into two groups: A very low-carb, high-fat diet group, and a habitual mixed Western diet group. Participants attended the exercise physiology laboratory at baseline, after two weeks (mid measurement) and at four weeks (post measurement) of the controlled experiment. A maximal incremental treadmill test was performed at baseline and four weeks, and a HIIT session was performed at all three times. Tests were separated by 48 hours.

Training sessions were conducted in the morning, three hours after participants’ last meal in a thermally controlled lab room. Participants were not to participate in vigorous activity 24 hours before lab testing. They were asked to perform 3 to 5 sessions per week of non-supervised training, to record their heart rate using a heart rate monitor, and to keep an exercise diary. Heart rate (HR), oxygen uptake (V̇O2), respiratory exchange ratio (RER), maximal fat oxidation rates (Fatmax) and blood lactate were measured.

High-intensity performance wasn’t found to be compromised during the final stages of the graded exercise test or the HIIT sessions.

Hindustan Times states that we don’t need a ton of carbs in our body to workout. A body is fine burning fat and can still perform well during a variety of exercises.

First of all, even if you’re on keto (low carb diet), it’s important to understand that you don’t need too much of carbs in your body. Your body will learn to use the fuel available (fats in this case) for the workout.

Even if your carb intake is restricted, you’ll be allowed a bit extra than the keto user that isn’t very active to give you the energy boost for your workout. Your body will burn through the carbs without impacting your keto progress.

Another study, this time by Obesity (Silver Spring) in October 2009, revealed that being on a keto diet combined with physical activity can increase weight loss and offer many health benefits.

Dietary restriction and increased physical activity are recommended for obesity treatment. Very low carbohydrate diets are used to promote weight loss, but their effects on physical function and exercise tolerance in overweight and obese individuals are largely unknown. The aim of this study was to compare the effects of a very low carbohydrate, high fat (LC) diet with a conventional high carbohydrate, low fat (HC) diet on aerobic capacity, fuel utilization during submaximal exercise, perceived exercise effort (RPE) and muscle strength. Sixty subjects (age: 49.2+/-1.2 years; BMI: 33.6+/-0.5 kg/m2) were randomly assigned to an energy restricted (approximately 6-7 MJ, 30% deficit), planned isocaloric LC or HC for 8 weeks. At baseline and week 8, subjects performed incremental treadmill exercise to exhaustion and handgrip and isometric knee extensor strength were assessed. Weight loss was greater in LC compared with HC (8.4+/-0.4% and 6.7+/-0.5%, respectively; P=0.01 time x diet). Peak oxygen uptake and heart rate were unchanged in both groups (P>0.17). Fat oxidation increased during submaximal exercise in LC but not HC (P<0.001 time x diet effect). On both diets, perception of effort during submaximal exercise and handgrip strength decreased (P<or=0.03 for time), but knee extensor strength remained unchanged (P>0.25). An LC weight loss diet shifted fuel utilization toward greater fat oxidation during exercise, but had no detrimental effect on maximal or submaximal markers of aerobic exercise performance or muscle strength compared with an HC diet. Further studies are required to determine the interaction of LC diets with regular exercise training and the long-term health effects.

Going on the keto diet has many health benefits, from losing weight to helping people combat diseases such as heart disease and diabetes. Combine the keto diet with exercise, which we discuss in the Body Reboot book, and you can experience incredible health results. To get a free copy of our book help us cover shipping and visit this page and get your copy today!

Sources: Hindustan Times, Forever Fit Science, Perfect Keto, NCBI: Metabolism. 2016 March, Ketovangelist, NCBI: Obesity (Silver Spring). 2009 October