Counting calories obsessively is not the key to trimming your waistline, according to a new study published Tuesday in JAMA. The study, from Stanford University researchers, found that what you eat is more important than how much you eat.
Researchers monitored the diets of more than 600 overweight adults. Even though the subjects didn’t cut back on calories, they lost an average of about 12 pounds over the course of a year. The results ranged from a reduction of 60 to a gain of 15 pounds.
The participants were randomly assigned to reduce fat or carbohydrate intake. During the study, they sat through 22 health education classes. They were also encouraged to be physically active. But the focus was on what they ate, and they were told to choose high-quality foods. The results are based on self-reports of their diet.
Both the low-carb and low-fat groups reduced their daily calorie intake by an average of about 500 calories.
But whether the individuals were assigned to the low-carb or low-fat group didn’t matter in terms of weight loss.
Not All Calories Are the Same
What did matter was the type of carbohydrates or fats they consumed: Those who ate the fewest processed foods, sugary drinks and unhealthy fats while eating the most vegetables also lost the most weight.
“If you reduce starch and sugar and you increase minimally processed healthful foods like vegetables, weight will go down naturally,” says Dariush Mozaffarian, a cardiologist and nutrition expert at Tufts University who was not connected to the study. “About 10 pounds a year, which is pretty substantial.”
Mozaffarian disagrees with the mantra that all carbs are bad. He says prior studies suggest big differences between different types of carbohydrates. “The carbs that we should be avoiding are those that come in high doses and are digested very quickly, what you might call fast carbs.” He recommends tossing out refined flours, potatoes and sugars and stocking up on fruits, beans or minimally processed whole grains.
Genetics and Insulin Levels Don’t Matter
At the beginning of the study, the participants underwent analysis to identify genetic variations that are linked to how the body processes fats or carbohydrates, which the researchers thought would make them more likely to lose weight on a low-fat or low-carb diet. Previous research had suggested that genes could interact with different types of diets to influence weight loss. The participants’ insulin levels were also taken.
Those who ate the fewest processed foods, sugary drinks and unhealthy fats while eating the most vegetables lost the most weight, regardless of whether they followed a low-carb or low-fat diet.
But neither their genetic makeup nor insulin resistance mattered in how successful the participants were in losing weight, the study found. These results suggest that “precision medicine is not as important as eating mindfully [and] getting rid of packaged, processed food,” said lead author Christopher Gardner. To achieve the former, he recommends avoiding screens while dining, shopping at farmers markets and sitting down for meals with friends and family.
Other Experts Weigh In
The study was well-conducted, said Dr. David Ludwig, a Boston Children’s Hospital obesity researcher, but because participants were not provided with specific foods and self-reported their choices, it wasn’t rigorous enough to disprove the idea that certain genes and insulin levels may affect which types of diets lead to weight loss.
Dr. Frank Hu, nutrition chief at Harvard’s School of Public Health, has called precision nutrition a promising approach and said the study wasn’t a comprehensive test of all gene variations that might affect individual responses to weight loss diets.
“In any weight loss diets, adherence to the diet and the overall quality of the diet are probably more important than any other factors,” Hu said.
Associated Press contributed to this report.
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