How Quickly Can You Lose Weight on No Carbs

The no-carb or low-carb diet was introduced by Dr. Atkins in 1972. It requires you to reduce or eliminate all carbohydrates from your diet and eat only proteins and fats. It may be an effective nutritional program for losing weight -- bodybuilders use a variation of it in the "cutting phase" of their season -- but MayoClinic.com questions its safety regarding heart health and digestive problems, and its ability to keep the weight off in the long term.

A baked salmon fillet over top of vegetables. (Image: Rafal Stachura/iStock/Getty Images)

How it Works

A lack of carbohydrates in the diet reduces levels of blood sugar and insulin and results in less glycogen stored in the liver to be used as energy. The body is then induced to use stored fat as energy. MayoClinic.com speculates there may be other reasons that a no-carb diet leads to weight loss, particularly in the short term: reduced carbs often have a diuretic effect -- a loss of water weight. Protein and fats take longer to digest, so a diet low in carbs and high in protein and fats will make you feel fuller for longer and inclined to eat less.

Long Term

Restrictive diets are often hard to sustain in the long term. This generally leads to the reversal of any initial weight loss. According to the New England Journal of Medicine, it is difficult to adhere to a very low-carb or no-carb diet for more than a few months at best, even with the help of dietitians and behavioral psychologists.

However, another study reported in the New England Journal of Medicine concluded that low-carb diets may be effective alternatives to low-fat diets. Test subjects on a low-carb diet in the two-year study lost an average of 5.5 kg compared to 3.3 kg for those on a low-fat diet.

Short Term

In an analysis of the Atkins or low-carb diet, MayoClinic.com refutes the claim that you can lose up to 15 lbs. in two weeks by eating only 20 g of carbs a day. MayoClinic.com makes the point that you can lose weight on any diet plan that restricts calories, particularly in the short term.

Possible Risks

According to MayoClinic.com, a low-carb diet, with an emphasis on high fat and animal protein, may increase the risk of heart disease and some cancers. The absence of grains from your diet may also lead to a nutritional deficiency, a lack of fiber and severe constipation. A lack of carbohydrates in the diet can also lead to ketosis, which occurs when the body is forced to use fat for energy because of the lack of glucose. As noted by the UK National Health Service, this causes an increase of ketones in the blood which can damage the kidneys and liver.

Possible Benefits

A low-carb diet may decrease overall cholesterol levels and increase levels of HDL -- high-density lip-proteins, also known as good cholesterol. This is the belief of Dr. Al Sears, an authority on heart health and owner of an integrative medicine and anti-aging clinic in Wellington, Florida. This seems to agree with the findings reported in the New England Journal of Medicine.