Low-carbohydrate diets or low carb diets, are food diet programs for weight loss and dietary health that advocate restricted carbohydrate consumption, based on research that ties carbohydrate consumption with increased blood insulin levels, and increased insulin with obesity.
Under these various dietary programs, foods containing carbohydrates (like sugar, grains, and starches) are limited or replaced in favor of foods containing more protein and fat. Vegetables, though classified as carbohydrates, are thought to be far healthier than grain-based carbohydrates. Programs such as the South Beach, Atkins and Zone diets, are claimed to "work" because they reduce insulin levels, which in turn causes the body to burn its fat for energy.
As a process, these kinds of diets have been in and out of fashion since the Banting diet appeared in the 19th century. But long before modern scientific invention, anecdotal and holistic prescriptions, containing passages about limiting certain foods, including foods of mostly carbohydrates, have appeared throughout history. Although strong evidence suggests, and general agreement claims, that low carb diets can help achieve weight loss, some have been controversial among nutritionists, and their relative safety has been challenged.
In 2004, a Canadian court ruled that foods sold in Canada could not be marketed with reduced or eliminated carbohydrate content as a selling point because carbohydrates were determined not to be a health risk, and that existing "low carb" and "no carb" packaging would have to be phased out by 2006.
Differences between low-carbohydrate diets
Low-carb diets are largely distinguished by the proportions of carb intake they recommend, and the method or methods used to determinine which source or sources of carbohydrates should be consumed and which should be avoided. While all agree that processed sugar should be eliminated, or at the very least greatly reduced, they often differ on the recommended levels of grains, fruits and vegetables, though there is broad agreement that, in general, vegetables are better than fruits, and fruits are better than grains.
Arguments for low-carbohydrate diets
The evolutionary argument
Some advocates of low carb diets believe that humans did not evolve to eat the typical modern Western diet, reliant on processed grains, starches, and refined sugar, and that their consumption causes undesired and largely unknown effects. Specifically, it is argued that they cause the body to produce excess amounts of the hormone insulin, which tells the body to store rather than burn fat, hence causing obesity and its complications (heart disease, cancer, diabetes). They claim that humans evolved to eat a diet which consisted mainly of meat and that the current "epidemic" of obesity is due to the popular assumption, reinforced by the food industry and the new field of dietary medicine, that the low-fat approach is healthier.
Supporters claim the exclusive focus on reducing fat is oversimplified, and that low-fat diets are not automatically healthy ones. They claim that the western world is not suffering from a collective failure of will to exercise, but has been encouraged to eat more carbohydrates, which in turn stimulate appetite and more eating.
The recent rise in western obesity rates has coincided with a widespread belief in low-fat, high-carbohydrate as a healthy way of eating. By contrast traditional, high-fat French cooking has led to a much lower incidence of obesity, morbid obesity and chronic heart disease than the high-sugar American diet, despite overall energy intake and exercise levels being the same.