Don’t Fear Fat

More evidence suggests that a high-fat, low-carb diet is better for weight loss than a low-fat diet, according to new research presented yesterday at the annual meeting of the American College of Sports Medicine in Denver.

The results aren’t shocking—we’ve told you to Stop Blaming Fat for years. Still, some news sites are reporting that saturated fat might be bad over time and to only indulge in fatty foods occasionally. We disagree. These results are more evidence to support the idea that fat isn’t the nutritional monster it’s been made out to be.

The study: Researchers at Johns Hopkins University studied 45 obese or overweight subjects who followed either a low-carb or low-fat diet to see if fat has a negative effect on the heart. The low-carb group had a diet of 40 percent fat and 35 to 40 percent carbs. The low-fat group had a diet of close to 30 percent fat and 55 percent carbs. Both groups ate about 1,600 calories a day.

Low-Carb = Faster Weight Loss

They evaluated each dieter when he or she lost 10 pounds. On average, it took the low-carb dieters 45 days to lose the weight, but it took the low-fat dieters 70 days.

Low-carb diets are more effective for weight loss because carbohydrates result in spikes of insulin, which make you hungrier, says Kerry Stewart, Ed.D., professor of medicine at Johns Hopkins and lead researcher.

Another reason for the rapid weight loss? “Low-carb diets cause excretion of sodium and water from the kidneys, making dieters lose water weight at first,” says Jeff Volek, Ph.D., and professor at the University of Connecticut. “Initially, this is desirable but it’s important to increase salt intake in the long-term.” Note: They won’t measure body composition until the end of the study, so we don’t know how much of the groups’ weight loss was water, muscle, or fat.

Weight Loss and Your Heart

After the groups lost 10 pounds, researchers measured endothelial function—a measure of vein and artery health—and arterial stiffness. They found no difference between the groups. They’ll be taking blood work when the study ends in about 2 months, so we’ll have to wait to learn the numbers for blood pressure and cholesterol.

Kerry attributes the lack of difference to weight loss. “My theory is that if people can achieve weight loss, it will benefit vasculature in every other system of body,” he told abcNews. “Weight loss, in the long run, will count more than the specific content of the diet.”

The Big Fat Debate

But wait, isn’t fat—especially saturated fat—bad for you? No. Research doesn’t actually support the theory that saturated fat makes you fat or hurts your heart. Consider this fact we cited in What if Bad Fat is Good For You? The Woman’s Health Initiative, a large, $725 million study, found that a diet low in total fat and saturated fat had no impact in reducing heart disease and stroke rates in 20,000 women who followed the regimen for an average of 8 years.

In the past, low-carb, high-fat diet opponents have used research on blood vessels to suggest that this nutritional approach is dangerous to your heart health. However, those studies have often overfed people fat—read: lots and lots of it at a single sitting—then simply measured the effect on blood vessels a few hours later. (In this study that fed people a big fast-food breakfast, the harmful vascular effects were only seen in people with the largest waist sizes—suggesting once again that weight may be the most important factor.) This hardly relates to how someone might follow, say, the Atkins diet in real life. In fact, in a University of Connecticut study, scientists found that eating a low-carb, high-fat diet for 12 weeks improves arteries’ flexibility.

Keep in mind that the Johns Hopkins study is ongoing and the results are preliminary. We’ll know in a couple of months how the rest of the heart-health numbers add up. But for now, take the results as more reason to question the overwhelming OMG fat is bad for you! mindset.