The Keto Diet and Exercise: The Ultimate Guide for Training on a Low-Carb Diet

This LEGO is trying a low-carb diet. Will it impact his running? Let's find out!

You’ve got questions about the Keto Diet and exercise, and we’ve got answers!

Our coaches help folks with their workouts and nutrition (it’s kind of our thing), and today we share with you the secrets of training under a low-carb diet. 

Here’s what we’re going to cover in our Keto + Exercise Guide today:

Real quick: if you are just starting your low-carb journey, make sure you grab our MASSIVE Beginner’s Guide to the Keto Diet. It’ll teach you everything you need to begin Keto. You can grab it for free when you join the Rebellion (that’s us!) by enlisting below: 

A Few Notes on Our Approach to the Keto Diet and Exercise

We’re going to approach this guide with a few caveats:

  • I don’t care what the “optimal” way to eat or train is. Unless you are an elite-level athlete or trying to build a specific physique, being “good enough” will suffice. This is true for your nutrition and for your training. The OPTIMAL way for you to train and eat is whatever method you will actually stick with long enough to build the habit!
  • We’ll look at what happens to your body on both cardio and strength training. You’ll be covered no matter what kind of exercise you follow.
  • You might suck at everything for the first few weeks of Keto. As pointed out in The Ketogenic Bible: “Significant declines in physical performance after one week of following a Ketogenic Diet; however, performance levels are restored after about six weeks, although it sometimes takes longer.”
  • The jury is still out on all of this – studies[1] have suggested that reducing carb consumption dramatically could impact performance negatively depending on the activity, and below I’ll show you studies that present the exact opposite conclusion. So…

Yep, we aren't quite sure how the Keto Diet will impact your training. But we'll explore some possible ways!

Alright, let’s do this thing…

The Keto Diet and Strength Training

“Steve, I like strength training. What does Keto look like for me?”

Great. I do too.

In fact, I train in a fasted state four days per week. When you strength train or train intensely, your body starts to use up the glycogen stored in your muscles.

Homer is ripped in this gif. But did he go low-carb to do it?

And you’re probably wondering “Steve if I don’t consume carbs, which becomes sugar, which my muscles store as glycogen…am I gonna run out of glycogen and my strength training might suffer?” 

Good question. Maybe.

“Does eating low-carb alter your body’s reliance on glycogen stores in the muscles? Does it change how much glycogen your muscles use or how quickly these stores are replenished?” 

Maybe. We’re still learning.

I did find multiple studies in which strength training was either not impacted or positively impacted by a Keto Diet:

  • A 2012 study[2] put 8 male gymnasts on a 30 day Keto Diet – they lost more fat mass and increased lean body mass while following the regimen. Suggesting Keto can help with body composition, which is probably why you are strength training to begin with.
  • A 2016 study[3] looking at CrossFit programming showed no significant difference in muscle mass or performance between a Keto group and the control group.
  • A 2017 study[4] worked with 25 strength training men – both groups gained muscle mass, while the Keto group lost more fat.

Now, this isn’t law, more studies are being done as we speak, and your results may vary. 

What this simply means is that there have been studies done that show one can do resistance training or Crossfit while eating Keto and not lose gains or muscle mass.[5]

Other studies show the opposite.[6] Which means…

Your results MAY vary. 

Like the wheel, it's had to determine exactly how you'll respond to the Keto Diet.

Make sure you give it enough time to push through the Keto flu, the performance-suckage phase, to get a true answer for your situation.

Also: unless you’re a competitive athlete or compete in powerlifting competitions, this might not matter as much!

Athletic performance is often negatively impacted once somebody gets to a low enough body fat percentage, but it doesn’t stop people from chasing that “ripped” six-pack abs look![7]

The Keto Diet and Cardio

“Steve, I’m a runner/biker/etc. and I always carbo-load. Sounds like Keto isn’t for me, right?”

Maybe not. 

Your body can only store 1600-2000 calories worth of glucose at any time – but might have 40,000+ calories worth of fat stored in the body. 

So instead of having to consistently eat gels and goos and snacks to keep the glucose levels high, what happens if you switch to “Keto-adapted” and fuel yourself with fat?

Let’s go to the science:

Earlier studies had suggested that a moderate-carb diet provides better endurance by increasing the concentration of glycogen in your muscles, but newer research seems to be swinging more in the direction of Keto.

As it turns out, the Keto Diet has been tested in ultramarathoners, Iron Man trainees, and endurance athletes, and in all cases, ketosis resulted in enhanced body composition and some of the highest rates of fat-burning ever recorded!

A 2016 study[8] looked at 20 ultra-marathoners and Ironman distance triathletes – half of which were instructed to be on a fat-adapted diet for at least 6 months and the other 10 were on a traditional carb-focused nutritional strategy.

The results:

  • Both groups had the same perceived level of exertion during a 3-hour trial run.
  • The Keto group had a fat oxidation rate of 2.3 times higher than the carb group, at an average of 1.5 grams per minute.
  • There were no significant differences in pre- or post-exercise glycogen concentrations.

Just like with strength training, this MIGHT work for you – or you might be better off as a carb-adapted runner and athlete. You have to do what works for you.

My above caveat still stands: unless you are an elite athlete, this should be less of a concern for you – follow the diet that makes you look and feel good, and then base your training progress of your previous day’s results!

The Keto Diet and Exercise for Weight Loss

“Steve, I’m not a competition-level ANYTHING, but I like exercising and want to look good.”

While dietary changes make up at least 80% of your weight-loss efforts, exercise will help you stay healthy and build a body you’re proud to look at in the mirror.

So track your workouts, track your nutrition, and work on getting better with it – running one second faster, doing one more rep, lifting 5 more pounds, etc. 

Compare yourself to your past self.

The Keto Diet and Athletic Performance

“Steve I read this study that says Keto + Athlete = good/bad/ugly.”

Fair. Do what works best for you! 

In my research, and in learning from people that I trust and admire in this space:

Studies are often focused on short term ketosis (a few days or weeks), which could result in adverse performance in athletes who have not become fully Keto-adapted yet.

We are all unique snowflakes and your mileage may vary depending on your physiology. So who cares if you lift 5 pounds less! 

If Keto works for you and makes you look better, keep doing that.

If you are going to try Keto + Strenuous Exercise, consider the following advice: Keto might work for you! It might not!

The recommendation from Dr. Steve Phinney:

  • Allow 2-4 weeks to become Keto adapted.
  • Make sure your electrolytes are in balance.
  • Eat enough protein to ensure your muscles are getting the tools they need to rebuild themselves.
  • See how your body responds – course-correct as necessary.

Elite performance chaser? Consider “targeted ketogenic dieting” – introducing timed carb intake strategically around training, which we’ll explore next. 

The Keto Diet and Carb Cycling for Athletes

“Steve, what’s up with carb cycling? How does that influence exercising on a low-carb diet.”

If you are an athlete and looking to maximize performance on a low-carb diet, consider “carb cycling.”

With carb cycling you follow a low-carb diet, but increase your carb intake around key events, generally training related.

So let’s say you have a really intense training session and want to replenish your glycogen levels. The evening or day after your training, you could perhaps double your carb intake.

This man is carb cycling on his Keto Diet, because pasta.

That’s carb cycling. 

Does it work?

There is some evidence to suggest it does.[9] Carbohydrates do indeed help muscles regain glucose when depleted, so the mechanisms of carb cycling tie out.

However, it should be noted that there isn’t much current research on a carb cycling diet. 

My advice: Only experiment with carb cycling if you are looking for top athletic performance. Otherwise, just keep your low-carb diet consistent. 

Getting Started Working Out on the Keto Diet

If you are convinced you should try the Keto Diet, and want to train while doing so, let’s provide some resources to get you going. 

First, if you have lots of questions on following a low-carb diet, read our Guide to the Keto Diet

It’ll explain the science behind a low-carb diet, menu ideas, and how to start the Keto Diet. 

Plus, there are ninja turtles in it. 

The Turtles celebrating a successful run on the Keto Diet.

What if you’re just starting your exercise journey? 

I got you boo:

  • The Beginner Bodyweight Workout: if you’re looking for a workout that you can do from the comfort of your own home, start here. It’s designed for a newbie and requires no equipment.
  • 5 Best Strength Training Workout Routines For Beginners: if you want to start a strength training practice (our number one recommendation for getting fit), start here. We’ll level up your workouts from simple bodyweight exercises to full compound movements with barbells.
  • 6 Beginner Gym Workouts: have a gym membership? Thinking about getting one? Then check out our full guide on becoming a gym warrior. 

With these resources in hand, you’ll have everything you need to start working out on the Keto Diet. 

However, we often hear from folks that they want MORE help. If that’s you, we built three great options to help you start your fitness journey:

#1) If you want step-by-step guidance, a custom strength training program that levels up as you get stronger, and a coach to keep you accountable, check out our killer 1-on-1 coaching program:

2) Good at following instructions? Check out our self-paced online course, the Nerd Fitness Academy.

The Academy has 20+ workouts for both bodyweight or weight training, a benchmark test to determine your starting workout, HD demonstrations of every movement, boss battles, meal plans, a questing system, and a supportive community.

3) Join the Rebellion! We need good people like you in our community, the Nerd Fitness Rebellion. 

Sign up in the box below to enlist and get The Beginner’s Guide to the Keto Diet. It’s all you need to start your low-carb journey.

That should just about do it for this guide. 

Alright, your turn:

Are you following the Keto Diet?

Have you noticed you perform differently while training under low-carb?

Any tips or tricks you’ve learned while exercising on Keto?

Let us know in the comments!

For the Rebellion,

-Steve

PS: Make sure you check out the rest of our guides on following a low-carb diet:

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Photo sources: Morning run with the Fitbit.

GIF sources: Rainbow Bright, Homer, Wheel, Pasta, Ninja Turtles.

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