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Today in Your Health, let's follow up on Friday's report on fat. Researchers have found that advice to cut back on eggs and meat may not help your heart or your weight. A big reason is what Americans started to eat instead.
NPR's Allison Aubrey explains.
ALLISON AUBREY, BYLINE: If you remember the 1990s, you might recall the fat-free boom that swept the country. Elizabeth Stafford, who's an attorney in North Carolina, was in college back then.
ELIZABETH STAFFORD: Oh, yes. I ate fat-free cookies, fat-free pudding or even cheese. Oh, a lot of fat-free cheese, which was awful.
AUBREY: The fat-free message was everywhere.
(SOUNDBITE OF AN AD)
UNIDENTIFIED MAN #1: So, you switched from whole milk to skim milk, huh?
UNIDENTIFIED WOMAN: Mm-hmm.
UNIDENTIFIED MAN #1: You're eating...
AUBREY: And if you hadn't made the switch, food marketers would remind you.
(SOUNDBITE OF AN AD)
UNIDENTIFIED MAN #2: Did you know that granola bar is loaded with fat?
AUBREY: Stafford says back in the in those days, she avoided all kinds of fats; cheese, eggs, meat, even nuts and avocados.
STAFFORD: No one cared about serving sizes or protein or anything like that. But it was always just making sure that it had zero fat.
AUBREY: Elizabeth was certainly not alone. A low-fat diet was what all the experts were recommending to prevent heart disease.
WALTER WILLETT: Fat was really the villain and by default, that meant you had to load up on carbohydrates.
AUBREY: That's Walter Willett of the Harvard School of Public Health. But he says as early as the mid-1990s, there were signs that this advice might not lead to fewer heart attacks or strokes. He had a long-term study underway evaluating the effects of diet and lifestyle on disease.
WILLETT: In those studies, we were following 40,000 men.
AUBREY: So he was able to analyze what happens when people ate less fat and more carbs.
WILLETT: We were finding that if people appeared to replace saturated fat with carbohydrate, there was no reduction in heart disease.
AUBREY: Willett submitted his findings to a top medical journal, but he says they wouldn't publish them.
WILLETT: There was a lot of resistance to anything that would question the low-fat guidelines, especially the saturated fat guidelines.
AUBREY: They were supported by highly influential groups, such as the American Heart Association.
WILLETT: It was a really conventional wisdom almost to the point of religion that saturated fats were the villain for heart disease.
AUBREY: Willett's paper was eventually published in 1996 in a British medical journal.
Now, it wasn't as scientists beginning to raise questions. After five or six years of low-fat eating, Elizabeth Stafford decided it wasn't working for her. She was gaining weight, as bagels and sugary yogurt she ate for breakfast left her hungry an hour later.
STAFFORD: I've constantly felt starving. And I constantly felt like I couldn't eat enough to be satisfied.
AUBREY: Now, nearly 20 later, a far more complicated picture has emerged of how fats and carbohydrates contribute to heart disease.
DARIUSH MOZAFFARIAN: You know, we've learned that carbohydrates aren't neutral.
AUBREY: That's Dariush Mozaffarian of Harvard Medical School.
MOZAFFARIAN: They used to be the base of the pyramid - eat all the carbohydrates you want. But carbohydrate's worse than glucose and insulin. They have negative effects on blood cholesterol levels. And most of our carbohydrates are highly refined and processed. And so, you know, thinking that that's just been OK, in a replacement for saturated fat, has actually not been useful advice.
AUBREY: And at the same time, Mozaffarian says scientists have been learning more about fat.
MOZAFFARIAN: Over the last decade, an enormous amount of scientific has indicated that the relationship between dietary fat and heart disease is not as clear as we once thought.
AUBREY: He explains case against saturated fat was made decades ago, when studies showed that foods - like meat, cheese and eggs -could raise one type of cholesterol. But there's been a lot more research since then.
MOZAFFARIAN: If you look at the whole picture of how saturated fat influences blood cholesterol levels - including its effects on LDL cholesterol, HDL cholesterol, triglycerides, many other complex factors - one would actually come to the conclusion that it has a relatively neutral effect on heart disease risk, compared to carbohydrate.
AUBREY: And research also shows that some facts, particularly plant-based fats such as olive oil and nuts - seem to have a beneficial effect on heart health. What's more, scientists now know that many factors influence the risk of heart disease. It's not just cholesterol; things like inflammation, blood pressure, glucose and insulin levels all play a role.
So where does this leave us? Well, many people are moving to a more moderate approach. Elizabeth Stafford is one of them. She now eats a bit more fat and far fewer carbs.
STAFFORD: It took me a long time not to be scared of it. But I realized how much better things taste and how much I missed making scrambled eggs with butter, or eating a hamburger.
AUBREY: It's not every day but she says the occasional burger no longer makes her feel guilty.
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