Is a Low Carbohydrate Diet Recommendable for Weight Loss

One of the areas of interest in nutrition in the last decade is the effect of low carbohydrate diets (LCD) on chronic diseases. When we search the articles in PubMed with MeSH term of Diet, Carbohydrate-Restricted [Mesh], we observed that the number of articles has been increased dramatically since 2000 (three articles in 2000 to 251 articles in 2017). LCD is referred to the diet that at least 40% of its energy comes from the fat even though; there is no accurate definition for the LCD due to the variation in macronutrient composition. Some kinds of LCD are ketogenic diet, Atkins diet, and Paleo Diet. One of the main factors for increasing the interest toward the LCD is unsuccessfulness of the low-fat diet in the reduction of the chronic diseases. In the 1970s, the percentage of macronutrients in the usual U.S. diet was 42% from fat, 12% from protein and 46% from carbohydrate. In 1977, the U.S. Senate Select Committee on Nutrition and Human Needs published controversial Dietary Goals for the United States for the sake of reduction of the chronic diseases. In this report, which was the predecessor of the Dietary Guidelines for Americans, it was recommended that the percentage of carbohydrate should be increased to 55% to 60% and the percentage of fat should be decreased to 30%. Following these recommendations, it has been expected that the prevalence of chronic diseases, especially cardiovascular diseases (CVDs) and one of its main risk factors namely, obesity become decreased. However, the prevalence and incidence of cardiovascular diseases and obesity has been increased since 1990. Following increasing the number of studies and improvement in the approaches to the study of diet-related chronic diseases, the perspective regarding the total fat intake has been changed and the types of the fat become the focus of attention. Accordingly, the tendency toward the use of low carbohydrate and high-fat diets has grown in recent years. In the LCD, the energy source of body shifts to a greater reliance on fatty acid oxidation that is associated with a reduction of insulin secretion, oxidative stress, inflammatory responses and improvements in many features of metabolic syndrome. Furthermore, people who use LCD for weight loss experience greater satiety during weight loss due to more stability in metabolic fuel availability. Following the beneficial effect of LCD on weight loss, several studies have been carried out to compare its efficacy with other weight loss approaches, especially low-fat diets. However, there is controversy in the findings of the performed studies; hence, several systematic review and meta-analysis have been performed to solve this discrepancy. Although there is controversy in the findings of the performed systematic review and meta-analysis; however, the most recent systematic reviews and meta-analyses have concluded that LCD has superiority for weight loss, compared to the low-fat diets. Besides obesity, one of the area of interest for LCD is its effect on other metabolic syndrome components including high triglycerides level, low levels of HDL, hypertension, and insulin resistance. Reduction in carbohydrate intake may improve these markers more effectively than do low-fat diets. However, it does not mean that people who are on the LCD have a lower risk of CVDs compared to the people who are on the low-fat diets because there are no long-term studies tracking CVD outcomes.In conclusion, according to the available evidence, LCD is a safe and effective in weight loss. However, to compare its efficacy on obesity and other CVD’s risk factors with low-fat diets and other approaches, we need long-term studies with a large sample size.