An Hour of Kickboxing, No Carbs
August 2017 — about two months in
I started keto in mid-June 2017 because home tests said my fasting glucose was too high, not because I was chasing a number on the scale (video cTGYIFOTPl8). But I was also a big guy who trained. Martial arts was part of my life before keto, and I wasn't going to quit kicking things because I'd quit bread. So one of the first practical questions I had to answer, for me and for the group, was whether you need carbs to train hard on keto.
By late August I had my own answer, and I put it in two short videos a day apart.
What happened on the mat
I'd been kickboxing on keto with no extra carbs at all: nothing before, nothing after. And in general I could keep my energy up through an hour or more of it (live FSBA7693). I did say you may notice you're a little flatter than usual right at the end of a workout. But a little flat at the end of an hour of kickboxing is not the same thing as "you need carbs."
So the video I made was about who actually needs to dose carbs, and the answer was: fewer people than you'd think (video XhEJ9x5sP0g).
- If you're doing keto for weight loss and your exercise is walking, jogging, an elliptical or light weights, you probably don't need carbs around your workouts at all.
- If you're doing something explosive, like competition CrossFit, sprint intervals, really heavy lifting mixed with intervals, track, wrestling, or a sport camp where you play several times a week, you may want to experiment.
- Experiment in practice, not on competition day. Your response depends on you and on the kind of carb you use.
- Timing: slow carbs like starches or crackers about an hour or two before; fast ones like a sports drink or honey closer to 30 minutes before. After a workout, somewhere from 30 to 90 minutes, up to about two hours.
- Amount: small. Something like 10 grams before and 10 after, see how you feel, and go up to 20 and 20 only if you really feel the benefit.
Carb dosing is a tool for performance and competition. It's not a requirement for ordinary training, and it's definitely not a requirement for losing weight.
What happened at the table
The next day I made a video telling people to stop eating so much fat (video NUJNFG6lLWw). I know. You just got used to the idea of eating fat. But once you're past the first month and fat adapted, your body fat is the fuel. Even a lean person has thousands of grams of it. So you don't need to chase your fat number every day. If you're past week five, you're not hungry, and the scale isn't moving, try cutting about 20 grams of fat a day. That's about 180 calories. Thirty grams is about 270.
And then I said what was actually happening with me. Some days I ate close to the calories I needed. Other days I ate about half, just because my hunger swung around. I didn't try to restrict it. But when I tracked it without restricting it, I tended to be in a deficit anyway (video NUJNFG6lLWw).
That's the part I keep coming back to. I was training an hour or more, eating no extra carbs, not forcing myself to eat less, and the numbers still showed a deficit. I wasn't white-knuckling anything. And I said it in that video: I don't encourage anybody on keto to go to bed hungry.
The lesson I took from that week: don't add things you don't need. Carbs for training, fat for "hitting your macros": both are things people tell you that you need. For most of us, most of the time, we don't.
What I'd tell you now
I'd still say most people training for health or weight loss don't need to dose carbs, and the workout-carbs chapter goes through who might. My "tracking showed a deficit anyway" line has held up, but I'd frame it more carefully. In a metabolic-ward study, adults lost body fat at 53 ± 6 g/day when the calorie cut came from carbs and 89 ± 6 g/day when it came from fat (Hall et al., 2015). That was a short ward study, not real life. But it says cutting carbs doesn't burn fat by magic. What keto did for me was make the deficit easy because I wasn't as hungry, and the deficit did the rest. That's in Energy balance on keto. If you take insulin or other glucose-lowering medication, talk to your doctor before you combine a low-carb diet with hard training.
Also worth a look: Keto for MMA and combat sports, Eating too much fat on keto, and the two videos, dosing carbs for hard workouts and eating too much fat.