Low-Carb Diet Research and News

By Ellen Coleman, RD, MA, MPH

Can a person eat unlimited calories, and still lose weight, as long as they severely restrict carbohydrates?

No, they cannot. The basis of ketogenic diets, such as the Atkins Diet, is a severe restriction of carbohydrate calories, which simply causes a net reduction in total calories. Since carbohydrate calories are limited, intake of fat usually increases. This high fat diet causes ketosis (increased blood ketones from fat breakdown) which suppresses hunger, and thus contributes to caloric restriction.

Low carbohydrate diets are also characterized by initial rapid weight loss, primarily due to excessive water loss. A decreased carbohydrate intake causes liver and muscle glycogen depletion, which causes a large loss of water, since about three parts of water are stored with one part of glycogen. Also, restricting carbohydrate intake reduces the kidney's ability to concentrate urine, leading to an increased excretion of sodium. All these factors combine to cause a powerful but temporary diuresis.

Dieters cherish this rapid initial weight loss and assume it represents fat loss. Actually, their body fat stores are virtually untouched. And, as the body adjusts for the water deficit, the weight loss slows or ceases. The dieter often becomes frustrated and abandons the diet. Individuals who do stick with it may lose weight due to the caloric restriction mentioned above.

A ketogenic diet may or may not have side effects, depending on the individual person. It is certainly riskier for overweight individuals with medical problems such as heart disease, hypertension, kidney disease, and diabetes than it is for overweight people with no health problems. Complications associated with low carbohydrate, high protein diets include ketosis, dehydration, electrolyte loss, calcium depletion, weakness (due to inadequate dietary carbohydrate), nausea (due to ketosis), and possibly kidney problems. Vitamin and mineral deficiencies are other problems in such unbalanced crash diet regimens. Even Dr. Atkins, the author of both old and new versions of Diet Revolution, admits that his diet doesn't supply enough vitamin and minerals and recommends that people take supplements.

Gout is another potential side effect, since the uric acid in the blood increases as the uric acid competes with ketones for excretion. This higher blood uric acid level can also increase the risk of kidney failure. Dr. Atkins does warn that people with kidney problems shouldn't follow his diet, but he doesn't mention that the diet might produce these disorders.

In the book The Ketogenic Diet, the author Lyle McDonald notes that the production of ketones from alcohol tends to result in less fat loss, since less free fatty acids are converted to ketones. He also indicates that there is no reason that small amounts of alcohol cannot be consumed during a ketogenic diet, although alcohol consumption slows fat loss. He cautions that alcohol may have a greater effect (in terms of intoxication) when someone is in ketosis.

Lastly, the risk of coronary heart disease may be higher in susceptible persons who stay on the diet a long time, due to increased consumption of foods high in saturated fat and cholesterol.

In conclusion, ketogenic diets such as Atkins' program are no more successful than those weight loss programs recommended by the scientific/medical community. They are more dangerous than other fad weight regimens due to its high fat content. Persons who choose to follow ketogenic diets should check with their physician periodically as the diet can cause electrolyte depletion and increased blood lipids. They should have periodic blood tests to measure total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides.