In the quest to tell us what we should be eating to live longer and healthier, nutrition science is either doing a bang-up job lately or causing mass confusion, depending on your point of view.
No doubt this isn’t the only article you’re likely to come across in the next day or so trumpeting the results of what’s being hailed as a major new study that finds people who stuck to a low-carb diet for a year lost more weight and were generally healthier than those who followed a low-fat diet.
Yep, that’s right: After years of health professionals tsk-tsking about the possible ill effects of forswearing carbs in favor of a return to steak and eggs for breakfast, it turns out ole Dr. Atkins might have been onto something after all.
Many nutritionists and doctors have “actively advised against” low-carb diets, Dr. Lydia A. Bazzano at Tulane University, a lead author of the new study, tells The New York Times. “It’s been thought that your saturated fat is, of course, going to increase, and then your cholesterol is going to go up. And then bad things will happen in general.”
That was before nutrition scientists began to question another long-standing bias against saturated fat, which many of us were raised to believe was the diet equivalent of the bogeyman, but we’ll get to that in a minute.
For the study, published this week in the Annals of Internal Medicine, researchers selected a group of approximately 150 people ages 22 to 75 with no history of diabetes or heart problems and randomly assigned them to stick to either a low-carb or a low-fat diet for a year. Notably, they were not required to cut the overall amount of calories they ate, just the amount of carbs or fat.
The low-fat group, for its part, reduced its total fat consumption to less than 30 percent of daily calories, which, as the Times notes, is consistent with federal dietary guidelines. The members of the low-carb group, on the other hand, increased the total amount of fat in their diets to more than 40 percent of daily calories, with a little more than 13 percent ultimately coming from saturated fat—more than double the limit set by, say, the American Heart Association.
The average weight loss for the low-fat dieters? Four pounds. And for the low-carb dieters? Almost 12 pounds. Yep, nearly three times as much.
Of course, there are lots of unhealthy ways to lose weight. What appears even more surprising than the dramatic difference in weight loss observed in the current study is how much healthier on the whole the low-carb dieters seemed to be than the low-fat ones.
Not only did the low-fat dieters lose more lean muscle than fat, but their levels of HDL cholesterol (aka good cholesterol) were lower than those of the low-carb group, while their risk for heart attack over the next decade, based on Framingham risk scores, remained more or less the same, according to the Times. The low-carb dieters managed to lower their scores.
From the standpoint of health researchers, the study achieved something of the gold standard: a clinical, randomized trial versus the type of observational studies that often pore over reams of data but can only determine correlation as opposed to cause and effect.
Yet such studies, by nature, are expensive and difficult to conduct, meaning their scope is often limited, in terms of both time and number of participants. The current study only tracked low-carb and low-fat dieters for a year, for example.
Nevertheless, the study is likely to enter the growing body of evidence that suggests nutrition experts have been way off in demonizing fat and, by extension, launching an unsuspecting public on a carb free-for-all. For more than a generation, cutting back on fat has meant ramping up our carb consumption, and it seems notable that today Americans are, on average, fatter than ever, and rates of obesity-related diseases such as diabetes have spiked.
Ultimately, it’s a steady diet of diet-related headlines that may be most hazardous to our health. Americans tend to glean the big news about nutrition research without understanding its nuances, which can lead to an all-or-nothing attitude about certain foods and a general sense that health scientists don’t know what the hell they’re talking about.
A huge study released last March by researchers at Harvard and Cambridge universities, for example, found no link between the consumption of saturated fats and heart disease, but even the study’s lead researchers were quick to caution that the findings shouldn’t be taken as a license to load up on bacon and ice cream.
Aaron E. Carroll, a professor at the Indiana University School of Medicine, may have hit the nail on the head last week in an article for The New York Times. Carroll starts by focusing on what recent science has revealed about our relationship with another age-old diet bugaboo: salt.
Yes, too much salt isn’t good for you, particularly if you have high blood pressure. But that’s led to a extreme reaction in the opposite direction, with the FDA, the World Health Organization, and the American Heart Association all advocating low-salt diets, setting limits of as little as 1.5 grams per day, when the average American consumes about 3.4 grams.
Guess what? A study published this month in the New England Journal of Medicine found that not only did people who consumed more than seven grams of salt a day have a higher risk of a “major cardiovascular event,” but the risk for people who consumed less than three grams was even greater.
“It’s a cliché but true: In so many things moderation is our best bet,” Carroll writes. “We have to learn that when one extreme is detrimental, it doesn’t mean the opposite is our safest course. It’s time to acknowledge that we may be going too far with many of our recommendations.”