How to choose the right low-carb diet

There's no denying the current popularity of low-carbohydrate diets. Chances are, you, or someone you know, has tried one. But do they work? What are the long-term health consequences of these diets? Here are some tips on picking the right low-carb diet.

The premise behind low-carbohydrate diets is that carbohydrate foods stimulate production of insulin, the hormone that is responsible for transporting glucose into the cells, where it is used for energy, with excess amounts being stored as fat. Since protein-rich foods do not cause the same rise in insulin levels, substituting them for carbohydrate foods promotes the use of stored fat for energy, resulting in weight loss.

• Low-carb diets range from extreme to more moderate.
• Some of the more extreme approaches, like Dr. Atkins or the South Beach diet, recommend a carbohydrate level of 20 or 30 grams (two tablespoons) per day during their initial stages.
• The current Recommended Dietary Allowance (RDA) for carbohydrate is a ­minimum of 130 grams (1/4 pound) per day, with most people eating well over 200 grams (1/2 pound) per day.
• More moderate diets, like The Zone, suggest carbohydrates represent 40 percent of calories (the current recommendation ranges from 45 to 65 percent), balanced with protein and fat at every meal.
• Many low-carb diets allow unlimited amounts of meat, poultry, fish, and eggs, non-starchy vegetables, nuts, seeds, oils and other fats.
• Some allow small amounts of fruits, dairy and whole grains.
• Processed carbohydrates, like breads, pastas, cereals and sugary foods, are restricted.

There's good evidence that during the first six months, low-carb diets can result in more rapid weight loss than conventional low-calorie, low-fat diets. Studies show that during this time, subjects on low-carb programs lose up to twice the weight as those on conventional diets.

• Low-carb diets can initially be easier to follow because the higher levels of protein and fat suppress appetite and keep dieters feeling full longer.
• When compared to conventional diets, low-carb diets, in the short term, may have a more beneficial effect on both HDL cholesterol (the "good" cholesterol) and triglyceride levels. Both these factors are important for cardiovascular health.

The early weight-loss effect of low-carb diets decreases over time. By about 12 months, there is no significant difference in weight loss using a low-carb diet versus a conventional approach with restricted calories and fat.

• Many of the stricter low-carb diets (like the Dr. Bernstein diet) put the body into ketosis. Ketosis is the accumulation in the blood of ketones, which are by-products of fat metabolism. Ketosis is not a normal body state and unless properly controlled can result in nausea, dehydration, dizziness, fatigue and bad breath.
• Because of the low-fibre, high-fat profile of many low-carb diets, constipation is often an unwanted side effect.
• The lack of variety of food choices, particularly in the beginning, can make the diet difficult to stick with in the longer term.
• The lack of variety also means that there is a potential for inadequate intakes of important vitamins and minerals.
•  The low-carb diets allow far less than the five to 10 servings of fruits and vegetables a day associated with good health.
• Scientific research has linked excessive meat consumption to colon and prostate cancer, and high protein intake with calcium loss from bones.