For middle-age adults trying to lose weight, is it better to cut back on carbs, like white bread, rice, crackers and cake, and not worry so much about fat? Or is fat the real evil, and you need to avoid eating too much meat, butter and cheese to drop those pounds?
Two new studies have slightly different answers.
A major new study from Tulane University found that cutting back on carbohydrates helped dieters lose significantly more weight and have better overall heart health than those who slashed fat from their diet.
On the other hand, a large study of popular diet plans, like Weight Watchers and Jenny Craig, found that both low-carb and low-fat strategies can help people lose weight. What’s most important is finding a diet you can stick with, concluded Canadian and American researchers. The study was published Sept. 3 in the Journal of the American Medical Association ( JAMA).
In the Tulane study, published Sept. 2 in the Annals of Internal Medicine, two groups of obese dieters, average age about 48, were followed for a year. Those who followed a low-carb diet lost three times as much weight as those who cut back on fat — 12 pounds compared to four.
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Perhaps more importantly, the low-carb group ended up with less overall body fat and more lean muscle, lower cholesterol and triglycerides, and lower levels of blood markers indicating inflammation than those who adhered to a low-fat regimen. The low-fat dieters lost more muscle than they did fat.
There weren’t many restrictions for either group in the study. The low-carb-ers ate a Mediterranean-type diet, heavy on fish, chicken and fat in the form of olive oil and nuts, but they could also eat some red meat, eggs and butter. In fact, breakfast each day was typically eggs. They had to keep carbohydrates, like pasta, potato products and bread, to no more than 30 percent of their daily calories.
The low-fat dieters were told to keep saturated fat — the kind found in meat and butter — to no more than 30 percent of calories, in line with current federal guidelines. They ate more grains, starches and cereal. Neither group changed its level of physical activity.
But cardiologist Dean Ornish is skeptical about the study’s conclusions. Ornish, who has done extensive research into reversing heart disease through a strict, low-fat diet (no more than 10 percent of daily calories), says studies have found that a low-carb diet can cause “greater blockage in the coronary arteries” than a low-fat diet, he wrote in an email.
“Our research has proven that a whole foods, plant-based diet naturally low in fat and in refined carbs (plus walking, meditating, and social support) can reverse the progression of even severe heart disease,” he said.
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Ornish also points out that there’s a big difference between “good carbs,” like fruits, vegetables and grains, and “bad carbs,” like sweets, white bread, chips and pretzels — and the study “didn't distinguish between good and bad.”
Indeed, a 2012 Harvard study published in JAMA found that diets high in refined carbohydrates may actually cause us to burn fewer calories.
When those on a low-carb diet stopped eating so many refined carbohydrates, they burned 150 more calories per day, compared with those on a high-carb, low-fat diet, study author David Ludwig, M.D., a professor of nutrition at Harvard’s School of Public Health, told NPR.org.
Think about that the next time you’re tempted to eat a doughnut.
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