For years now, the low carb diet has been at the center of a raging controversy. Enthusiasts say the diet is easy, virtually painless, and leads to rapid weight loss. Nutritionists and dietitians counter that the weight lost on a low carb diet is temporary and usually regained within a year. They also raise the specter of
and triglyceride levels as a result of the higher fat content in the diet. Enthusiasts counter that the metabolic changes triggered by the diet lowers blood sugar and insulin levels, which contribute to weight loss and better health. This continued back and forth led researchers to design a study that would assess the effect of a low carb diet on weight and other metabolic factors after one year.
The results of their study were published in the May 18, 2004 issue of the
Annals of Internal Medicine
. The researchers found that when it comes to total weight loss, low carb diets and conventional low fat diets yield similar outcomes after one year. They also found, surprisingly, that low carb diets offered more favorable metabolic outcomes than its low fat counterpart.
About the Study
The researchers studied 132 severely overweight adults, with a body mass index of at least 35. (Body mass index, or BMI is a convenient measure of a person’s weight relative to their stature. A normal BMI is 18 to 24. People with a BMI of 25 to 29 are considered overweight, and people with a BMI of 30 or more are considered obese.)
Each participant was randomly assigned to follow either a low carb or a low fat diet. In the low carb group, participants ate no more than 30 grams (g) of carbohydrates per day. In the low fat group, participants followed a diet that reduced their daily caloric intake by 500 calories per day, with less than 30% of their total caloric intake coming from fat. At the beginning of the study, each participant was weighed and blood samples were taken. This was repeated at six months and again at one year.
In the first six months of the study, the low carb group lost more weight more quickly than the low fat group. After one year, however, the researchers found no significant difference in the amount of weight lost by either group (11-19 pounds vs. 7-19 pounds, respectively). They did, however, find that participants who followed the low carb diet had improved triglyceride and HDL (favorable) cholesterol levels and favorable blood sugar control over those who followed the conventional low fat diet.
How Does This Affect You?
The researchers concluded that despite the fact that both groups in the study lost similar amounts of weight, the group following the low carb diet achieved a better health outcome because their overall triglyceride levels were reduced and their HDL cholesterol levels were increased.
A second study published in the same issue of the
followed 120 overweight people for six months and found that participants on a low carb diet lost an average of 26 pounds, compared to an average of 14 pounds lost by participants on a low-fat diet. Again, in this study, those who followed the low carb diet had more beneficial changes in triglyceride and HDL levels than those on the low fat diet.
An editorial, also published in the May 18, 2004 issue of the Annals concluded that, based on the results of these two studies, dietitians and nutritionists can no longer dismiss low carb diets. Instead, overweight patients should be encouraged to experiment with various methods of losing and then maintaining their weight, and that these methods may include low carb diets as long as they include healthy sources of fat and protein and are supplemented by daily exercise.
In the end, of course, the recipe for long-term, healthy weight loss remains the same: reduce the number of calories you eat (diet) while increasing the number of calories you burn (exercise).
Almost any diet can lead to weight loss over the short term. The true test of the low carb diet, as with any diet, is its ability to produce steady, persistent weight loss and improved health outcomes over the long haul. While the metabolic changes found in this study are reassuring, the true test will be if the diet leads to lower rates of diabetes, stroke, and coronary heart disease. Until this is known, however, it appears the low carb diet does have a legitimate place in the much-needed thinning of America. On the other, hand it is clearly no magic bullet.
Stern L, Iqbal N, Seshadri P et al. The effects of low carbohydrate versus conventional weight loss diets in severely obese adults: one-year follow-up of a randomized trial. Ann Intern Med. 2004;140:778-785.
Willett WC. Reduced-carbohydrate diets: no roll in weight management? Ann Intern Med. 2004;140:836-837.
Yancy WS, Olsen MK, Guyton JR, et al. a low carbohydrate, ketogenic diet versus a low fat diet to treat obesity and hyperlipidemia. Ann Intern Med. 2004;140:769-777.
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