Fat is back, new research shows.
This latest study
, released Monday in the new edition of Lancet Diabetes & Endocrinology, does not give you free reign to chow down on pizza or to have that second dessert, but it does give you license to have that egg for breakfast if you cook it in olive oil, rather than butter, and forgo the side of bacon or toasted white bread.
The study -- from scientists looking at the weight and waist circumference of 7,447 people who ate three different diets for five years in a randomized control study -- suggests that a Mediterranean diet (versus a low-fat diet, in which you avoid all fat) is more successful in helping you lose a little weight. This is true even if you are older, have type 2 diabetes or are already obese or overweight.
A Mediterranean diet -- one of the recommended options with the updated dietary guidelines -- is heavy on vegetables and legumes, fish, fruit, nuts and whole grains. The food is cooked with olive oil. Carnivores on the diet keep poultry and lean cuts of meat on the menu. Red meat, processed food and sugar are off the table.
Researchers figured this out by comparing data from men between the ages of 55 and 90 and women between 60 and 80 years old. About 90% of the people in the study were overweight or obese when they started the trial and either had type 2 diabetes or had high cholesterol or high blood pressure or were smokers.
Scientists split the people into three groups; one stuck with a Mediterranean diet and was given extra-virgin olive oil donated by an olive oil company to cook their meals. Another group ate a Mediterranean diet and was given a mix of nuts by a nut company to add to their diets. Another group was advised to avoid all dietary fat. Each group was given some dietary counseling through the five years of the study. None of the groups was given advice about exercise.
All three groups lost a little bit of weight. The group that was given the extra-virgin olive oil and ate the Mediterranean diet did the best. There was a significant weight loss at both the three- and five-year mark compared with the group eating the low-fat diet. This group lost about 2 pounds, while the low-fat group lost 1.3 pounds.
Those who ate more nuts along with the Mediterranean diet saw a slight loss of weight after three years and what was considered a significant decrease at five years, compared with where they started, but it was not very different from the low-fat group.
Waist size did go up slightly for all three groups. The low-fat dieters saw the biggest increase, of 1.2 centimeters (about 0.47 inches), compared with 0.85 centimeters (about 0.33 inches) for the olive oil group. The group that got extra nuts went up the least: about 0.37 centimeters (about 0.14 inches).
The ultimate takeaway from this study was that the fat found in the Mediterranean diet -- olive oil, fatty fish, nuts -- isn't bad for you at all.
The advice doctors used to give patients about avoiding all fat in order to have a healthy heart and lose weight or maintain your weight isn't accurate.
This isn't the first study to point this out. The new dietary guidelines
, which are based on updated science
, put no cap on fat
like in past years. But some of the examples from the new guidelines offer caveats when recommending nuts or cooking with olive oil, suggesting that your intake of both be in moderation.
Dr. Dariush Mozaffarian,
a cardiologist and epidemiologist who wrote an editorial that accompanied the current study, suggests, based on this new research, that the guidelines should lose those caveats.
"They don't have caveats with fruits and vegetables but do with fat. And this study shows we should get rid of that fear of fat," Mozaffarian said.
Mozaffarian, dean of the Tufts Friedman School of Nutrition Science & Policy, believes that because fat is more energy-dense and higher in calories, doctors mistakenly advocated that patients try a low-fat diet. But that, he said, oversimplified the issue.
He points to a study
he did that looked one high-fat food: cheese. It's the food "everyone mistakenly linked to weight gain," he said. The study found that when people replaced carbs with cheese, they didn't gain any more weight, and they had the added benefit of a lower diabetes risk. Some cheese also has beneficial bacteria that may be good for the microbiome in your gut.
"A handful of nuts may be 160 calories, which is more calories than a can of Coke, but that doesn't mean the can of Coke is a better choice," Mozaffarian said. Salt, sugar, starch, processed food and trans fats should be off the menu, not fat. "Healthy foods are healthy foods, and bad foods are bad. It doesn't matter if the food is low-fat or high-fat. This is a separate issue."