8 Things You Need to Know About Exercising on the Keto Diet 1. You might not feel so great at first. "Your brain's primary fuel source is glucose (from carbs), so as it switches over to ketone bodies created by breaking down fats in the liver, it will take some adjusting." –Ramsey Bergeron, C.P.T. 2. The first few weeks on keto is not the best time to try a new workout. This initial icky period can be dubbed the "keto flu" thanks to its flu-like grogginess and stomach upset. 3. It's super important to eat enough. When you cut out a food group, you're more likely to under eat. And the keto diet can have an appetite-suppressing effect, so you might feel full when you really haven't eaten enough to fuel your workout. 4. You could burn more fat during cardio. "If you are following aerobic exercises such as running or biking, a keto diet can help increase fat oxidation, spare glycogen, produce less lactate and use less oxygen." –Lisa Booth, R.D.N. 5. You really, really need to eat enough healthy fat. Without enough fat to compensate for the carbs you're missing, you're likely to feel tired and miss out on actually going into ketosis. 6. Keto could help you reach your body composition goals. "Studies have shown that ketogenic diets coupled with moderate-intensity exercise can positively affect one's body composition," –Chelsea Axe, D.C., C.S.C.S. 7. You might need to rethink your favorite HIIT workouts. HIIT workouts use glycogen no matter your intake. Since glycogen stores are fueled by carbs, performance can suffer when on a keto diet. 8. Listening to your body is crucial. "Your health and well-being should be the most important thing. Add some more carbs and see how you feel. If this makes you feel better, the keto diet might not be the right choice for you." –Lisa Booth, R.D.N.