The rapid increase in obesity that began in the 1980s coincides with the emphasis on low fat diets and the food pyramid promoting grain and carbohydrate consumption in place of fat. While this is only circumstantial evidence, a large number of studies now show the low fat dietary approach to be wrong.
A review of data from 23 random controlled trials comparing low carbohydrate and low fat diets showed most of the studies were conducted on people with health problems, including obesity, Type 2 diabetes and metabolic syndrome. The low carbohydrate groups often lost two to three times as much weight as the low fat groups. This is despite the fact that in most cases, calories were restricted in the low fat groups, while the low carb groups could eat as much as they wanted. When the researchers looked at abdominal fat (the unhealthy visceral fat) directly, low carb diets had a clear advantage.