Low-carbohydrate diets or carbohydrate-restricted diets (CRDs) are diets that restrict carbohydrate consumption. Foods high in carbohydrates (e.g., sugar, bread, pasta) are limited or replaced with foods containing a higher percentage of fats and moderate protein (e.g., meat, poultry, fish, shellfish, eggs, cheese, nuts, and seeds) and other foods low in carbohydrates (e.g., most salad vegetables such as spinach, kale, chard and collards), although other vegetables and fruits (especially berries) are often allowed.
There is a lack of standardization of how much carbohydrate low-carbohydrate diets must have, and this has complicated research. One definition, from the American Academy of Family Physicians, specifies low-carbohydrate diets as having less than 20% carbohydrate content.
Disadvantages of the diet might include halitosis, headache and constipation, and in general the potential adverse effects of the diet are under-researched, particularly for more serious possible risks such as for bone health and cancer incidence.
Carbohydrate-restricted diets can be as effective, or marginally more effective, than low-fat diets in helping achieve weight loss in the short term. In the long term, effective weight maintenance depends on calorie restriction, not the ratio of macronutrients in a diet. The hypothesis proposed by diet advocates that carbohydrate causes undue fat accumulation via the medium of insulin, and that low-carbohydrate diets have a “metabolic advantage”, has been falsified by experiment.
Carbohydrate-restricted diets are no more effective than a conventional healthy diet in preventing the onset of type 2 diabetes, but for people with type 2 diabetes they are a viable option for losing weight or helping with glycemic control. Carbohydrate-restricted dieting does not appear to be helpful in managing type 1 diabetes. The American Diabetes Association recommend that people with diabetes should adopt a generally healthy diet, rather than a diet focused on carbohydrate or other macronutrients