Carbohydrates do raise blood sugar, because they provide so much of your body’s preferred source of fuel: glucose. When glucose levels rise, your pancreas releases a flood of insulin that prompts cells to store sugar. Advocates say that eating a diet low in carb makes weight loss easier because low, steady blood sugar conquers food cravings. But the next step in the low-carb equation is open to debate: Proponents say these diets also change your metabolism so your body breaks down more fats, and--voilà --fewer of the calories you eat are stored as flab.
Low-carb weight-loss plans do work--for a while. Pounds drop quickly at first because burning stored carbs (called glycogen) releases water. Quite simply, you lose excess water weight. Nutritionists say, though, that low-carb weight loss isn’t metabolic magic, just the working-out of nature’s first rule of weight loss: Eat fewer calories, and you will shed pounds. Some low-carbers say this special way of eating eliminates cravings, but others feel headachy and nauseated. Burning far without carbohydrates produces substances called ketones, which can decrease appetite, but there’s a danger because sustained high ketone levels may deplete mineral stores in bones, leaving them fragile. Here’s the rest of the low-carb story.
Low-carb diets don't go the distance for weight loss.Carb-conscious eating may speed up early weight loss, but not much more. In a year-long study of 63 dieters, University of Pennsylvania researchers found that low-carb dieters dropped 4 percent more weight than those following a conventional low-cal plan in the first six months--but both groups achieved nearly identical weight losses after one year.
When researchers at the National Weight Control Registry looked at the diets of 2,681 successful dieters who had maintained at least a 30-pound weight loss for a year or more, they expected to see many low-carb diet adherents. They were shocked to find just 25, or 1 percent of the total group. Their conclusion: Low-carb plans didn’t produce a lasting metabolic change that kept pounds off.
A high-fat, super-low-carb diet threatens your heart. The Atkins Diet--the oldest and most famous of the low-carb regimens--allows a mere 20 grams of carbs per day in the earliest, strictest phase, putting most grains, beans, fruits, breads, rice, potatoes, pastas, and starchy vegetables off-limits. At the same time, it allows generous amounts of beef, pork, chicken, eggs, and butter.
Unlimited access to bacon cheeseburgers is tempting, but a low-carb diet that’s essentially an all-you-can-eat saturated-fat buffet may increase your risk of heart attack and stroke, the American Heart Association cautions. All that sat fat can raise levels of heart-threatening LDL cholesterol--and at the same time shortchange you on the antioxidants from fruits, veggies, and grains that protect arteries from plaque formation. (Low-carb diets are also high in protein, which makes them risky for people with diabetes because they can speed the progression of diabetic kidney disease.)
Low-carb isn't low-calorie.Many low-carb products undermine weight-loss efforts because they’re packed with as many--or even more--calories than "regular carb" versions. Many are also higher in fat. This is especially true of reduced-carb comfort foods such as ice cream, bread, pasta, and snack bars. A 1-ounce low-carb chocolate bar with 120 calories or a 270-calorie scoop of low-carb Rocky Road ice cream won’t do your hips any favors.
"It’s the calories, not the carbohydrates," notes Robert O. Bonow, M.D., former president of the American Heart Association. "America is gaining weight because people are eating more calories than they can burn and getting less exercise."
Low-carb junk food is still . . . junk.Indulging in a low-carb snack food with the belief that it’s a better weight-loss choice than a piece of fruit, a serving of veggies, or a handful of whole grain crackers (trans fat-free, of course) puts you in double jeopardy: You’ve just robbed your body of a host of heart-healthy nutrients and fiber, and you may have eaten a ton of empty calories. Example: For 40 grams of carbs a day, you could eat 1/2 cup of lentils, a cup of carrots, an orange, and a slice of light seven-grain bread (total calories: 40; plus a hefty dose of antioxidants, vitamins, and minerals). Getting those 40 grams from low-carb snack foods could supply up to 1,440 calories and very few nutrients.
