Yes, I’m a personal trainer and nutrition coach. You can exercise and you should! I’ve lost 7 lbs and 15 inches in the last two weeks and I have not stopped exercising nor have a lost muscle mass. But it has to be done carefully. Here’s the deal (sorry for the long explanation): Your body burns macro nutrients (carbs, protein and fat) in just that order. Carbs first, then protein, then fat. Carbs are broken down into sugar, which is your bodies quickest form of energy. When it doesn’t have sugar to use, it then turns to stored muscle glycogen (a form of sugar) to burn. When it not longer has that, then it turns to protein (a. k. a. your muscle). Because we are in ketosis, we don’t have any sugar in our bloodstream or stored muscle glycogen for the body to use. So in order to give you the energy needed to support exercise, it has to burn muscle, which is obviously not what you want. Sooooo, in order to continue to exercise and not break down muscle you need to take care to do two things: 1) watch the intensity of your workout. If you are unable to talk, you are working to hard. It means you are working without oxygen or anerobic. When you are anerobic, your body uses protein (your muscle) for fuel and not fat because it takes more time to break down fat into useable energy. And when you are working at that intensity, your body needs energy ASAP! So keeping your heart rate and breathing I check will keep you in an aerobic state and burning fat instead of muscle. 2) be sure to take a branched chain amino acid supplement (IP’s are really yummy) either during or immediately after your workout. Amino acids are the building blocks of muscle and exercise is catabolic (meaning it breaks down muscle). So in order to help rebuild what you’ve just broken down by exercise, you need to give your body a little “boost” with the BCAA. Our bodies are amazing and the layers of metabolic processes that it has in place to keep us alive are incredible. Just knowing a little about how it works definitely helps you work this program a little better. So long answer to a short question is yes, do exercise. Just take care to mind your heart rate and take a BCAA. Hope that helps!