Keto Exercise Part 1: How To Exercise While You Keto-Adapt

If you’re 100% satisfied with your Keto exercise routine, then all you’ll likely get from this article are a few interesting factoids about working out as a Keto beginner. 

And there’s nothing wrong with that. You can impress your friends with your knowledge of Keto-adaptation. 

But if you’re struggling with exercise on Keto (especially if you’re just starting a Keto diet), you’ll get more than just trivia. You’ll get practical guidance on improving your life.

After all, exercise is a pillar of good health, right up there with sleep and nutrition. Being active every day can help you lose fat, improve your mood, boost your immunity, and decrease your risk for a host of chronic diseases.[*] 

And until they invent an exercise pill, you have to go do it. Keto or otherwise. 

This article is the first in a three-part series on Keto exercise. You’ll learn the basics of Keto-adaptation, how carbs factor in, and which exercises are best for Keto beginners.

What Is Keto-Adaptation?   

Coined by long-time Keto researcher Dr. Stephen Phinney, Keto-adaptation simply means adapting to using fat for energy. 

The process of keto-adaptation, or fat-adaptation, typically takes several weeks of carb restriction on a Keto diet.[*] For most people, this means keeping carbs at around 5-10% of daily calories, filling in the rest with fat and protein.  

Why must carbs be limited to fat-adapt? Because high intakes of carbohydrates raise blood sugar and insulin levels, and high circulating insulin prevents the breakdown of body fat. Insulin is a fat-storage (not a fat-burning) hormone.[*]  

When you limit carbs, insulin levels fall. This tells your cells: Ah, carbs are scarce, we need to look elsewhere for energy! 

That elsewhere is body fat. And when you can access body fat, it’s like hitting the energy jackpot.  

That’s because you can store way more energy in fat cells (triglycerides) than you can in glycogen, your storage form of carbs. You can store a mere 2,000 calories in glycogen. But in fat, even a lean athlete has about 40,000 calories socked away.[*] That’s a difference of 20x!

Picture two endurance athletes. One must constantly refuel her carb tank. The other can access 40,000 additional calories of body fat. Advantage, Keto athlete. 

We’ll dive into Keto endurance exercise in a later article, but for now, understand that fat can fuel longer efforts just fine. This is supported, in case you were wondering, by research on Keto-adapted ultra-endurance athletes.[*]

Do You Need Carbs for Exercise?

Many types of exercise—especially the harder, longer efforts—rely heavily on carbs for fuel. These exercises are known as glycolytic because they demand glucose.  

For the non-keto-adapted person, eating carbs may help enhance performance during these exercises.

Does this mean you can’t perform these exercises optimally on Keto? Not necessarily. 

First of all, you can experiment with carbs with a Cyclical Ketogenic Diet or Targeted Ketogenic Diet. See this guide to Keto exercise for more info. 

But before experimenting with carbs, it’s wise to Keto-adapt for at least four weeks. Keto-adapting should help you fuel all types of exercise—not just the low-intensity exercise associated with the “fat-burning zone”.

In fact, there are many published examples of people performing better after adapting to Keto. For instance, in 1980 Dr. Stephen Phinney and colleagues famously showed that obese people—after several weeks of Keto dieting—could go for twice as long on the treadmill.[*] More recently, research has shown that Keto dieting plus resistance training is a good way to lose fat while maintaining muscle mass, and in some cases, even gain muscle mass.[*] To be clear, however, Keto is not the best diet for building large muscles.[*] You need higher carbs to build large muscles efficiently. 

Note that studies showing good athletic performance on Keto gave participants 8 to 12 weeks to Keto-adapt. What does this mean for you? During your time of transition, you’ll want to moderate your training regimen. 

Exercise While You Keto-Adapt

In the early stages of Keto dieting, your body will be used to running on carbs for energy. It takes time to train your cells to run on fat. 

Once you Keto-adapt, you should be able to handle (and benefit from) high-intensity training like sprints, Crossfit, or other hard efforts. That’s because keto-adapted athletes can:

1. Burn more fat to fuel exercise
2. Preserve glycogen more efficiently, saving it up for glucose-demanding efforts[*]

But during the first four to eight weeks of Keto dieting, consider taking it easier than you normally would. 

This doesn’t mean you should post up on the couch for two months. Just be mindful that harder exercise may place undue demands on your body.  

With that in mind, here are three categories of exercise to ease you into Keto: 

#1: LISS

LISS, or low intensity sustained state cardio, will form the bedrock of your exercise routine as you fat-adapt. Light jogging, cycling, swimming, hiking, and walking are all fair game.

A good rule of thumb for LISS? Give it about 50% of your max effort, or max heart rate. You should be able to comfortably sustain these activities for at least an hour. 

#2: Easy Strength Training

To maintain strength while Keto-adapting, focus on high-rep low-weight resistance training. Bodyweight exercises like push-ups, planks, lunges, and squats are ideal. 

Keeping it light helps you stay out of the anaerobic (glucose demanding) zone. But don’t worry, you can crank up the weight once you fat-adapt. Later in this series, you’ll learn all about building strength on Keto. 

#3: Balance, Flexibility, and Stability Training

If you want to stay functionally fit into your later decades, strength and endurance alone won’t cut it. You also need to bring balance, flexibility, and stability into your regimen. 

Yoga and pilates are great all-in-one options here. Again, stick to the easier classes for the first few weeks of Keto. Save the 100-degree power vinyasa class for after you fat-adapt. 

Getting Started With Keto Exercise

Did this article cover everything about the Keto diet and exercise? Of course not. 

But it should help you exercise smarter as you begin your Keto journey. Future articles in this series will cover the nuances of strength and endurance training on Keto, including how to modify your Keto diet to suit your specific situation. 

For more on this topic—weight loss considerations, peak performance, adding carbs, tracking macros, and more—check out Carb Manager’s comprehensive guide to Keto exercise.