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Am Fam Physician. 2006;73(11):1951

See related article on low-carbohydrate diets.

What is a low-carbohydrate diet?

Foods get their calories from protein, fats, and carbohydrates. Most of the calories you eat come from carbohydrates and fats. Carbohydrates are starches and sugars, which are in foods like bread, pasta, and sweets. Low-carbohydrate diets (or low-carb diets, for short) cut down on the amount of calories you get from sugars and starches.

People on low-carb diets eat less bread, pasta, potatoes, rice, and cereals. They usually eat more vegetables, meat, fish, cheese, eggs, and nuts.

Do these diets help people lose weight?

Whenever people eat fewer calories than their bodies use, they lose weight. People on a low-carb diet usually take in fewer calories, even though they are eating more protein and fats than usual. Low-carb diets have been shown to help people who are overweight lose weight. These diets may work better than low-fat diets when people first start dieting. After the first six months, though, low-carb diets do not work any better than other diets.

Are low-carb diets safe?

It is probably safe to go on a low-carb diet for up to one year, but doctors are not sure if these diets are safe for longer than that. Low-carb diets do not raise cholesterol levels for most people. In fact, they may improve your cholesterol level if you lose weight. Some people on these diets may have constipation, diarrhea, dizziness, bad breath, headaches, sleeping problems, or nausea.

If you have had a stroke or if you have diabetes, heart disease, high cholesterol levels, or kidney stones, or if you are pregnant, talk to your doctor before starting a low-carb diet.

Should I take vitamins when I'm on a low-carb diet?

Yes. People on low-carb diets may not get enough vitamins, minerals, and fiber. If you are on a low-carb diet, you should take a multivitamin and a fiber supplement (one brand: Metamucil) every day.

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