When it comes to exercise on keto, there are plenty of rumors scattered across the internet.
You can’t build muscle on a keto diet. You need to “carb up” for endurance exercise. You can’t train at high intensity on a low-carb diet.
If you’re eating keto to improve your health—to lose fat, boost your energy, and feel more alert—this is all rather confusing.
Exercise is a pillar of good health. You don’t want to give it up, post up on the couch, and lose your strength.
Must you sacrifice exercise to stay keto?
Not at all. Early on, you’ll want to make a few tweaks. But as you adapt to the keto diet, you can exercise as usual.
Before getting to these tweaks, let’s talk about the main objection to keto exercise: Carbohydrates.
Do You Need Carbs To Fuel Exercise?
The short answer is no. The long answer requires some explanation.
Your body runs on two main fuel sources: Glucose (from carbs) and fatty acids (from fat).
Glucose is the “preferred” fuel. This means that, when glucose is available, your body burns glucose before burning fat.
Glucose is also the preferred fuel for intense exercise. These glycolytic activities include CrossFit, marathons, box jumps, high intensity interval training (HIIT), obstacle racing, and powerlifting.
Glycolytic exercises burn through glucose like nothing else. And “carbing up” before, during, and after exercise helps fuel them.
But you don’t need carbs to fuel these exercises. Why? Because your body has glucose backup systems. In other words, glucose supplies can be replenished without eating carbs.
The first system is glycogen. Your body stores about 500 grams of glucose (as glycogen) in muscle and ~100 grams in liver cells. During exercise, that glucose gets released. Instant energy fuel.
The second is gluconeogenesis. Believe it or not, your body can synthesize glucose from foods, like protein and other non-carbohydrate carbon substrates. How cool is that?
Combined, these glucose-backup systems help fuel glycolytic exercise in a low-carb state.
Doing keto also reduces the need for glucose. When you can effectively utilize fat for fuel, less glucose is required.
How does this affect aerobic exercise? Let’s find out!
Aerobic Exercise on Keto
In 1980, a young researcher named Stephen Phinney published a small study showing keto could enhance endurance exercise.
In the study, Dr. Phinney and his colleagues put six people with obesity on a ketogenic diet for six weeks. The goal was to examine how keto would affect the participants’ performance on the treadmill.
It had a profound effect. Participants stayed on the treadmill nearly twice as long after keto-adapting. With fat as their primary fuel, their exercise capacity greatly increased.
More recent research had similar results:
- 2016 study: Compared to high-carb athletes, keto-adapted athletes burned 2.3 times more fat while running.
- 2017 study: Endurance athletes from New Zealand showed improvements in body composition and mood after ten weeks of keto dieting.
It appears that fat isn’t just an alternate fuel for endurance exercise, it’s better fuel.
But can a high-fat diet also work for building strength?
Building Muscle On Keto
Some say it’s impossible to build muscle on a very low-carb diet. Why? Because low-carb diets suppress insulin, a hormone that stimulates growth.
But here’s the thing. You may only need a bit of insulin—not tons of it—to build muscle. The real non-negotiables for gaining strength are:
- Resistance training
On a keto diet, you eat 20 to 30 percent of your calories from protein—plenty for synthesizing muscle. But any old protein won’t do. You want a protein, like meat or whey, that’s high in leucine.
Leucine is the king (or queen) of amino acids for muscle growth and repair. And ketones (the energy bundles produced on a keto diet) have a fascinating relationship with Leucine. They work together to preserve and synthesize muscle.
This is intriguing, but is there any clinical research? Yes! In one study, resistance-trained men on keto diets added more muscle than controls on high-carb diets.
The bottom line? You can build muscle and strength on keto.
Keto Exercise For Beginners
When you first go keto, it takes several weeks to adapt to fat as fuel. During this time, you may feel like you’ve lost your mojo during exercise.
This is normal. The shift from burning glucose to burning fat doesn’t happen overnight. Your cells need time to transition, and you should be kind to them while they do.
In most cases, this means taking it easier than you normally would. If you’re an avid CrossFitter, for instance, you might skip a few WODs. If you’re a marathoner, you might take a break from heavy training.
Intense or long-duration exercise, if you recall, demands extra glucose. And before you keto-adapt, your body won’t be ready to meet those demands.
This doesn’t mean you shouldn’t exercise in the early stages of keto. You should. But while you fat-adapt, your activity level should be light to moderate.
Consider these three buckets of exercise for keto beginners:
- Easy aerobic exercise. Light cardio like hiking, swimming, biking, cycling, and jogging (40 to 50 percent of max heart rate) nicely compliment keto-adaption. These activities are known as low intensity steady state (LISS) cardio.
- Easy strength training. High-rep low-weight resistance exercise helps you stay strong while you fat-adapt.
- Balance and flexibility. Yoga, pilates, and stretching keep you loose, limber, strong, supple, and injury-free. Stick to the easier classes for the first few weeks of your keto journey.
Tips For Keto Exercise
To wrap up, here are some quicks tips to kick off your keto exercise program:
- Allow 4 to 6 weeks of keto before hard exercise. This allows time for fat-adaptation.
- Eat 0.5 to 1 gram of protein per pound of body weight. Combine with a resistance training program to maintain or build muscle.
- Eat enough calories. Exercise increases your caloric needs. Consider bringing some keto-friendly snacks along!
- Hydrate properly. Take electrolytes like sodium, potassium, and magnesium along with water to prevent deficiencies and “keto flu” symptoms.
- Be active every day. Exercise has countless benefits, from mood boosts to better sleep to a better appearance.
Oh and one last thing: Have fun! Exercise shouldn’t be a chore. Find something you like doing and stick with it. See you out there.
Author: Brian Stanton
Bio: Brian Stanton is the author of Keto Intermittent Fasting, a certified health coach, and an expert in the keto diet, fasting, and gut health. Follow Brian’s work by visiting his website at www.primalsapien.com.