“Low-carb may trump low-fat in diet wars,” declared ABC News in September. Really? Let’s look closer.
The study that spurred the headlines pitted a lower-carb diet against a lower-fat diet in 148 men and women who averaged about 215 pounds when they entered the study. After one year, the lower-carb group lost more weight (12 pounds) than the lower-fat group (4 pounds).
That’s no surprise, given that the lower-fat eaters made smaller changes to their diets than the lower-carb eaters (who cut not just carbs but also fat).
The lower-fat assignment “was, essentially, a diet intervention that didn’t intervene much with their diets,” wrote David Katz, of the Yale-Griffin Prevention Research Center, in the Huffington Post.
What’s more, asking whether a low-fat or low-carb diet is best for losing weight is “a truly lousy question,” Katz noted. “Everything from lentils to lollipops is carbohydrate. Fats run the gamut from good to bad to ugly. I’m pretty sure everybody not stuck under a boulder knows that.”
“This idea about low-carb versus low-fat needs to stop,” says Bradley Johnston, assistant professor of epidemiology at McMaster University in Hamilton, Canada.
“We’ve invested huge amounts of resources into low-fat or low-carb diets, and it’s misguided to keep driving this message to the public.”
Johnston recently did a meta-analysis of 49 trials of “branded” diets—including low-carb (like Atkins, South Beach, and Zone) and low-fat (like Ornish and Rosemary Conley), and blends of the two (like The Biggest Loser, Jenny Craig, and Weight Watchers).
“The differences were minimal,” he says. “People on the low-carb or low-fat diets lost slightly more weight than people on the blends. But people may adhere better to blends because they reflect how we typically eat.”
The largest, longest studies of non-branded diets also find no dif¬ference. And even when studies report more weight loss on a low-carb diet, the difference is small.
For example, in the DIRECT trial, which involved 322 people who averaged 200 pounds, those on a low-carb diet lost 10 pounds after two years, while those on a low-fat diet lost 6 pounds.9 But four years after the study ended, the low-carb group had gained back more weight than the low-fat group, so the difference between groups was no longer statistically significant.
“At the end of the day, if someone can’t follow a diet for 2, 3, or 4 years, it’s not going to be any good to them,” says Johnston. “What’s important is picking a diet that’s healthy and that you can stick to over the long term.”
Bottom Line: To lose weight, try cutting carbs or fat or both. Odds are, when you cut carbs, you’ll also cut fat (and calories) because many “carbs”—like pizza, french fries, burritos, lo mein, sandwiches, lasagna, cookies, ice cream, doughnuts, chips, popcorn, pastries, and chocolate—are also fatty.
Sources: JAMA 297: 969, 2007; N. Engl. J. Med. 359: 229, 2008; Ann. Intern. Med. 161: 309, 2014; JAMA 312: 923, 2014; N. Engl. J. Med. 360: 859, 2009; JAMA 293: 43, 2005; Ann. Intern. Med. 153: 147, 2010; N. Engl. J. Med. 367: 1373, 2012.
Other relevant links:
• What the research shows about the Paleo Diet and weight loss. See: Evidence for the Paleo Diet and Weight Loss?
• Can coconut oil help you lose weight? See: Coconut Oil and Weight Loss
• Low-carb diets and weight loss. See: Diet and Weight Loss: It’s Time to Curb Carbs