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. Low-carbohydrate diets are associated with increased mortality, and they can miss out on the health benefits afforded by high-quality carbohydrate such as is found in legumes including grain legumes or pulses, and fruit and vegetables. 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. It is not clear how low-carbohydrate dieting affects cardiovascular health; any benefit from HDL cholesterol might be offset by raised LDL cholesterol, which risks causing clogged arteries in the long term. 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. There is little evidence that low-carbohydrate dieting is helpful in managing type 1 diabetes. The American Diabetes Association recommends that people with diabetes should adopt a generally healthy diet, rather than a diet focused on carbohydrate or other macronutrients. An extreme form of low-carbohydrate diet – the ketogenic diet – is established as a medical diet for treating epilepsy. Through celebrity endorsement it has become a popular weight-loss fad diet, but there is no evidence of any distinctive benefit for this purpose, and it may have a number of initial side effects. The British Dietetic Association named it one of the 'top 5 worst celeb diets to avoid in 2018'.