"The Key to Weight Loss Is Diet Quality, Not Quantity, a New Study Finds," reported the New York Times online in 2018. Here's what the study actually found.

The study, called DietFits, was designed to see if people lose more weight on a healthy low-fat diet or a healthy low-carb diet.

“Healthy” meant minimally processed whole foods, not junk

"We told everyone in both groups to eat as little white flour and sugar and as many higher-fiber vegetables as possible,” says lead investigator Christopher Gardner, professor of medicine at Stanford University.

The year-long trial, involving 609 people, was funded by the National Institutes of Health and the Nutrition Science Initiative.

The low-fat group was advised to eat high-quality carbs like lentils, low-fat yogurt, steel-cut oats, quinoa, fresh fruit, and beans. The low-carb group was told to eat high-quality fats like salmon, avocados, nuts, seeds, hard cheeses, and olive oil.

And no one told the participants to cut calories. “If you prescribe calorie restriction, people feel deprived,” says Gardner. “So we just said, ‘Eat as low as you can on fat or carbs and don’t be hungry.’”

The results

Whether they cut fat or carbs, “each group reported a 500-calorie reduction,” says Gardner. And after a year, the people in each group had lost an average of about 12 pounds.

In other words, when it comes to weight loss, it doesn’t matter if you cut carbs or fat. Although the study participants weren't told to count calories, calories still mattered.

“Dr. Gardner said it is not that calories don’t matter,” explained the Times, near the end of the article.

What’s more, the study couldn’t show that “The Key to Weight Loss is Diet Quality, Not Quantity," because it didn't compare diet quality to quantity. (To do that, Gardner would have had to tell a third group of dieters to count calories.)

DietFits' most surprising finding

It didn’t matter if people were resistant to their body’s insulin when they entered the study.

“We assumed that insulin-resistant people would do better on a low-carb diet—as they did in some earlier studies—but they didn’t,” says Gardner.

Maybe that’s because both groups were told to eat healthy foods, he suggests. “In some older studies, when researchers told people to eat less fat, they weren’t particular about which low-fat foods. Coke and white flour and sugar are low-fat.”

Gardner also noted that—as in earlier studies—the results varied dramatically. “Someone lost 60 pounds, someone gained 20 pounds, and we saw everything in between,” he says. “The range, which was similar in both diet groups, was stunning.”

The bottom line

You can lose as much weight on a healthy low-fat diet as a healthy low-carb diet. If you find it cumbersome to count calories, eat as little white flour and  added sugar and as many fiber-rich vegetables as possible. You'll likely end up cutting calories without thinking about it, but that doesn't mean that calories don't matter.

Photo: Sweetgreen.

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