Is it okay to work out hard while on a low-carb diet?

If you’re a really serious athlete, the answer is probably no. The problem, says William Evans, chief of the nutrition, metabolism and exercise lab at the University of Arkansas for Medical Sciences, is that “whenever you work out hard, you use glycogen, the body’s stored form of glucose (sugar). If you don’t eat much carbohydrate, your muscles will have ever-diminishing levels of glycogen and it will be difficult to continue exercising. There’s a lot of research that demonstrates that a high carbohydrate diet is important for people who do a lot of exercise.”