Glucose, easily made from carbohydrates, is your body's preferred energy source. A ketonic diet helps your body burn stored fat for energy, instead of glucose. Most low-carb diets are ketonic, also called ketogenic -- the word comes from "ketones," an acidic chemical by-product produced when your body converts fat into fuel. The Atkins diet is an excellent example of a ketonic diet plan.
Ketonic Diet Basics
A ketonic diet limits carbohydrates, which your body is readily able to convert into glucose. A ketogenic eating plan substitutes protein and fat for carbohydrates in your diet. A ketonic diet shouldn't eliminate all carbs. You'll still need to eat high-fiber vegetables and a limited amount of fruit, but it will restrict starchy vegetables such as potatoes, corn and peas, as well as most grains, some legumes and all refined sugars. Ketosis, a condition caused by incomplete fat breakdown, is a concern with ketogenic diets. Ketosis can cause weakness, nausea, dehydration, dizziness and irritability. You'll know if you're in ketosis by checking your urine; special test strips can measure the amount of ketones your body is excreting.
Ketogenic Diets and Insulin
Only carbohydrates raise your blood sugar and cause your body to release insulin. Fat, protein and fiber slow the absorption of sugar into your bloodstream and help stabilize glucose levels. One theory behind ketogenic diets and weight loss is that having less insulin helps eliminate food cravings. Because your blood sugar is stable, episodes of hypoglycemia, low blood sugar, don't trigger attacks of sudden hunger and subsequent binge eating. If you consume fewer calories, you'll lose weight.
Ketonic Diet Plans
Ketonic diets appeal to a lot of people because they generally don't involve calorie counting or portion control. You can eat as much as you like of animal protein and fats, while restricting sweets, breads, pastas, most fruits and starchy vegetables. For example, the strictest phase of the Atkins diet allows for up to 20 grams of net carbs a day; a net carb is the total carbohydrate count in grams minus the grams of fiber in a food. So if a vegetable has 3 grams of carbs and 2 grams of fiber, it has 1 gram of net carb. This should allow you enough vegetables to meet your daily nutritional requirement, although you still may need to take a vitamin supplement.
The Dangers of Ketonic Diets
Ketonic diets may be safe in the short-term, but more research is needed about long-term health effects of restricting carbohydrates. Side-effects of ketonic diets can include dehydration, dizziness, irritability and bad breath. Although ketones are mainly excreted in your urine, excess ketones also leave your body in your perspiration and breath -- and ketones don't smell good. A high protein diet can be very high in saturated fat and cholesterol, which may raise your risk of heart disease.