You’ll Feel Terrible
Low-carb diets usually begin with an “induction” phase that eliminates nearly every source of carbohydrate. Often, you’ll consume as few as 20 grams of carbohydrate a day. That’s less than 100 calories’ worth—about what’s in a small dinner roll. On a 1,200-calorie diet, that’s only about eight per cent of your daily calories. By contrast, health experts recommend that we get between 45 and 65 per cent of our calories from carbs.
When carbohydrate consumption falls below 100 grams, the body usually responds by burning muscle tissue for the glycogen (stored glucose) it contains. When those glycogen stores start to run out, the body resorts to burning body fat. But that’s a very inefficient, complicated way to produce blood sugar. The body tries to do it only when it absolutely has to (such as when it’s starving)—and for good reason. Turning fat into blood sugar comes at a price in the form of by-products called ketones. They make your breath smell funny. They can also make you tired, lightheaded, headachy, and nauseated. Feeling lousy is certainly one way to dampen the appetite, but not one that most people would choose.
With virtually no carbs in your system, you may even have trouble concentrating. According to the Institute of Medicine of the National Academy of Sciences, the human brain requires the equivalent of 130 grams of carbohydrate a day to function optimally—and that’s a minimum.