Lyle,
I’m wanting to maximize my results on a CKD (BodyOpus) diet. I have the diet down to a science where I can start first thing Monday AM & enter ketosis by Tuesday afternoon. In addition to doing cardio work, I also try and throw in a couple of extra circuit weight training days. I was a little confused in reading your last couple of articles. I believe you mentioned that despite being in ketosis (where your body prefers ketones over carbs), weight training while in a ketogenic state, still burns glycogen from muscle cells. As a result, weight training has little effect on burning extra fat. Did I interpret this correctly?
A: Yes and no. During weight training (actually, any high intensity training), glycogen/glucose is the only substrate which can be used for fuel. In addition, after about week 3 of a ketogenic diet, the muscles have stopped using ketones for fuel for the most part, the brain is the only tissue which uses ketones to a significant degree at this point. So in one sense, weight training has no effect on fat loss, in that muscles don’t use fat (or ketones) for fuel during weight training.
However weight training has some indirect effects on fat loss.
1. After weight training, there exists something called the Excess Post-exercise Oxygen consumption (EPOC) which is basically the difference between how much energy your body needed (during the workout) and how much you could provide it. EPOC is much higher following high intensity exercise than low intensity exercise and it will be repaid from fat (since rest is the lowest intensity you can achieve).
2. Protein synthesis is elevated following weight training and, in all likelihood, the ATP for protein synthesis is coming from fat.
3. 2 recent studies (one in obese individuals, one in lean) found that depleting muscle glycogen made it easier for the body to adapt to a high fat diet. That is, the more muscle glycogen which is present, the less fat your muscles tend to use for fuel at rest. So by lowering muscle glycogen, you improve your overall fat burning capacity. You simply have to be careful not to deplete *too* much glycogen or you can start using protein for fuel.
I plan on extending ketosis out for 7-10 days before a carb-up day. What I would like to know is, am I better of doing mild cardio work instead of mild workout days?
It depends on a lot of factors, the biggest of which is your total training volume. If you read my article “Training on the CKD“, you’ll see that a certain amount of volume is necessary to fully deplete glycogen between carb-ups. The workout I designed is set up to deplete most of that glycogen on Monday and Tuesday but I don’t see any reason you couldn’t stretch that out over a longer period.
That is, one person I know had excellent results with a 10 day cycle. He did:
Day 1/2: normal upper/lower split
Day 3/4: cardio
Day 5: short depletion (basically what you’re asking about)
Day 6-9: cardio
Day 10: finish depletion, carb-up and then start over
About the author
Lyle McDonald+ is the author of the Ketogenic Diet as well as the Rapid Fat Loss Handbook and the Guide to Flexible Dieting. He has been interested in all aspects of human performance physiology since becoming involved in competitive sports as a teenager. Pursuing a degree in Physiological Sciences from UCLA, he has devoted nearly 20 years of his life to studying human physiology and the science, art and practice of human performance, muscle gain, fat loss and body recomposition.