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Weight loss

Most people can lose weight on diet plans that restrict calories and what you can eat — at least in the short term. And low-carb diets, especially very low-carb diets, may lead to greater short-term weight loss than low-fat diets.

But most studies have found that at 12 or 24 months, the benefits of a low-carb diet are not very large. A 2014 review found that higher protein, low-carbohydrate diets may offer a slight advantage in terms of weight loss and loss of fat mass compared to a normal protein diet. At a year, the difference was only about a pound (about 0.4 kilograms), though, and those who had the greatest benefits stuck to the diet long term.

Cutting calories and carbs may not be the only reason for the weight loss. Some studies show that you may shed some weight because you eat less on low-carb diets because the extra protein and fat keep you feeling full longer.

Other health benefits

Low-carb diets may help prevent or improve serious health conditions, such as metabolic syndrome, diabetes, high blood pressure and cardiovascular disease. In fact, almost any diet that helps you shed excess weight can reduce or even reverse risk factors for cardiovascular disease and diabetes. Most weight-loss diets — not just low-carb diets — may improve blood cholesterol or blood sugar levels, at least temporarily.

Low-carb diets may improve HDL cholesterol and triglyceride values slightly more than do moderate-carb diets. That may not only be due to how many carbs you eat but also the quality of your other food choices. Lean protein (fish, poultry, legumes), healthy fats (monounsaturated and polyunsaturated) and unprocessed carbs — such as whole grains, legumes, vegetables, fruits and low-fat dairy products — are generally healthier choices.

A report from the American Heart Association, the American College of Cardiology and he Obesity Society concluded that there isn't enough evidence to say whether most low-carbohydrate diets provide heart-healthy benefits.

Risks

If you suddenly and drastically cut carbs, you may experience a variety of temporary health effects, including:

  • Headache
  • Bad breath
  • Weakness
  • Fatigue
  • Constipation or diarrhea

In addition, some diets restrict carbohydrate intake so much that in the long term they can result in vitamin or mineral deficiencies, bone loss, and gastrointestinal disturbances and may increase risks for various chronic diseases.

Severely restricting carbohydrates to less than 20 grams a day can result in a process called ketosis. Ketosis occurs when you don't have enough sugar (glucose) for energy, so your body breaks down stored fat, causing ketones to build up in your body. Side effects from ketosis can include nausea, headache, mental and physical fatigue, and bad breath.

It's not clear what kind of possible long-term health risks a low-carb diet may pose because most research studies have lasted less than a year. Some health experts believe that if you eat large amounts of fat and protein from animal sources your risk of heart disease or certain cancers may actually increase.

Sep. 18, 2014 See more In-depth