The Lowdown on Low Carb Diets
Do they work? Are they safe? Here's the latest.
According to the alarming statistics, most Americans need to take off more than a few pounds. But for overweight people with diabetes, losing weight is crucial; even modest weight loss –– 5 to 10 pounds –– can get you better glucose control, cholesterol numbers, and blood pressure. Add to this the fact that limiting carbohydrates is an important strategy in managing blood sugar, and you can see why people with diabetes would be inclined to try one of the popular low-carbohydrate diets. Is it a good idea?
The Great Carb Debate
Most experts believe that cutting your intake of one type of macronutrient (fat, protein, or carbohydrate) is not a good way to lose weight. Most also believe that eliminating high-carb foods while consuming unlimited protein and fat is unhealthy –– citing nutrient deficiencies, potential kidney problems, bone loss, and elevation in cholesterol. These experts, along with the American Heart Association and most mainstream health organizations, promote calorie cutting and increased activity for weight loss. Many recommend following the U.S. Dietary Guidelines represented by the Food Pyramid (which is a high-carb diet). The American Diabetes Association, however, changed their position in the 2008 version of their clinical guidelines for physicians. They ceded that low-carb eating had been proven safe and effective for losing weight, at least at one year of follow-up.
Low-carb proponents say that by drastically reducing the amount of carbohydrates you consume, you switch your body's fuel source from carbs to fat, thereby "burning" body fat more quickly. Proponents also say that losing weight by restricting carbs preferentially burns abdominal or visceral fat –– the fat around your middle (which you have if you are the owner of an "apple" rather than a "pear" shaped body) that does the most damage in terms of diabetes and heart disease risk.
New Conventional Wisdom
Most people know that refined carbohydrates –– wheat flour and sugar, primarily –– are not good for you, and some people believe that eating too much of them puts excess pounds on you. Many also now know that these carbohydrates are converted very quickly into glucose and generally cause a rapid rise in blood sugar levels –– which is not good for people in general, but is especially dangerous for those with diabetes.
If you have diabetes, the primary issue with low-carb dieting is that these diets can be high in saturated fat, which has been shown to raise LDL ("bad") cholesterol. Atkins, for instance, does not limit the amount of animal fat you can consume. The South Beach Diet allows only "lean" cuts of beef (4.5 grams of saturated fat or less per serving), but doesn't limit portion size. Since diabetes puts you at an increased risk for heart disease, increased LDL cholesterol is a serious concern. Some research shows, however, that saturated fat in the context of a low-carb diet does not raise LDL cholesterol. Because of the paucity of studies and confounding factors (e.g., weight loss alone improves cholesterol), the jury is still out on this issue.
The great debate about what is the healthiest way to eat has been left largely unresolved because of this lack of long-term research. Recently, however, scientists analyzed data from more than 82 thousand women enrolled in the Nurses Health Study, which was conducted over the course of 20 years. This is the first study to look at the long-term effects of eating a low-carbohydrate diet. The women who ate the lowest amount of carbohydrates did not have any greater incidence of heart disease, and those eating a low-carbohydrate diet that was rich in vegetable sources of fat and protein had a 30 percent lower incidence of heart disease.
The bottom line? If you have diabetes, you have to watch your carbohydrate foods, and stick to those that have the least extreme glycemic impact. So, in essence, you are already on a low-carb diet. If you need to lose weight, however, you may need to take things one step further. But keep in mind: None of the popular low-carb plans are magic bullets, the jury is still out on long-term effects, and what works for one person may not for another. Before deciding on a weight-loss plan, talk to your health care provider, dietitian or certified diabetes educator (CDE).
Reviewed by Susan Weiner, R.D., M.S., C.D.E., C.D.N. 3/08
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