Many questions remain unanswered regarding the long-term effects of low-carbohydrate diets for doctors to recommend them to their patients. Patients who want to try these diets need to be told that although safety cannot be guaranteed, they seem to be safe for short-term use (up to six months) as long as weight loss occurs. Researchers from the RVA University in Copenhagen, Germany, did a review of low-carbohydrate diets and found that only three studies have reported on diets sustained for more than 90 days. There was greater weight loss with a low-carbohydrate diet after six months than with low calorie diets. However, in the two studies that were extended to 12 months, there was no difference between the two types of diets. The researchers concluded that what is needed are studies lasting long enough to assess the diet's effects on risk factors for heart attack and stroke, such as cholesterol levels. More information is also needed regarding fibre and micronutrient composition, as well as effects on markers of kidney and bone health, nutritional adequacy, dietary compliance, quality of life and cancer risk. Until then, the best recommendation, for people who want to lose weight and keep it off, is a permanent switch to a diet low in calories and fat in combination with physical activity.
The Lancet,
August 2004