How does a low carb diet work?

When people eat carbohydrates, the human body releases insulin into the blood. Insulin is the hormone that enables the absorption of sugar by the cells. Its role is to burn down the sugar molecules that circulate in the blood and to diminish the harmful effects that high levels of sugar have on the body.

By the activity of insulin, carbohydrates are converted into fat. In the process, insulin prevents the fat cells from releasing fat into the blood and burning it. Thus, the body begins to deposit fat as a side effect of insulin. That is the reason why the popular low carb diets, such as the Atkins, South Beach, or Protein Power, permit an average intake of thirty grams of carbohydrate per day. At that level, the insulin levels in the blood system are kept down and the body burns all the fat consumed and released from the fat cells. This is why people lose so much weight when they cut down on carbs. Another side effect of insulin is the stimulation of hunger signals to the brain. The result is craving for more and more carbs, which leads to their increased consumption and to repetition of the cycle.

The control of insulin levels by decreasing the intake of carbohydrates breaks this vicious cycle. When the carbohydrate intake is restricted, the insulin level goes down and the level of glucagon increases. Glucagon is a hormone that stimulates the burning of body fat and the removal of cholesterol from the arteries.

When people drastically cut down on carbs in their diet, (e.g. to up to 30 grams daily), the body quickly goes into a condition called "ketosis"- i.e. the burning of fat with the production of ketone bodies in the bloodstream. Ketones are mild acids, a sort of reserve fuel released from the burned fats with the purpose of survival under the conditions of famine.


The result of ketosis is stabilization of the blood sugar levels, decrease of the insulin level, and since the body is burning fat, weight loss.

Diets that cause the body to go into ketosis are called ketogenic. A ketogenic diet is the most efficient way of significant reduction of the body weight. Some nutritional experts believe that ketosis is a harmless condition. However, others claim that there are a few dangers of ketogenic diets. The most significant one is the risk associated with ketosis itself. Doctors warn pregnant women, alcoholics, or people with kidney or liver disease never to go on a ketogenic diet.

Other side effects include headache, tiredness, and lethargy, loss of appetite, weakness and, in extreme cases, diarrhea and nausea. In addition, a person on a diet that is extremely poor in carbohydrates, fiber, and many vitamins and minerals is prone to feel irritable, lethargic, and depressed.

On the positive side, the ketones released with ketogenic diets reduce the release of insulin and the stress hormones. As a result, the blood sugar becomes more stable, hunger is calmed down, and anxiety is reduced.