Here’s why experts are rethinking their recommendations to eat less fat and cholesterol.
For decades, fat and cholesterol were the enemy. Our moms told us so—as did the Food Pyramid, our doctors, and the bulk of research out there.
Most experts agree it all started with the Framingham Heart Study. Launched in 1948, it sought to ID the top risk factors of heart disease by looking at the health and habits of 5,209 adults who lived in Framingham, Massachusetts. While the study is currently investigating the third generations of residents there, the first iteration of study results had some weak points. Among them, the assertion that high intakes of dietary fat and cholesterol increase the risk of developing heart disease.
“It seemed like an easy assumption to make, that the more fat and cholesterol you ate, the more fat you’d gain and the higher your blood cholesterol levels would be,” explains says Susan Kleiner, PhD, RD, a sports nutrition consultant and author of Power Eating. And other research throughout the ’70s, ’80s, and ’90s seemed to agree. So egg-white omelets became a thing and every brand of chips and ice cream came out with a low-fat and fat-free version. It seemed everyone was following a low-fat, low-cholesterol diet.
The Truth About Fat and Cholesterol
“But that assumption was an oversimplification of weight gain and heart disease,” says Kleiner, who notes that dietary cholesterol has very little influence on blood cholesterol levels. After all, in 2003, a study published in the British Journal of Nutrition found that people who replaced saturated fats with unsaturated ones for just four weeks lost weight—without cutting calories. A 2015 Harvard meta-analysis concluded that low-fat diets aren’t successful for long-term weight loss. And a 2014 Annals of Internal Medicine meta-analysis of 512,420 people concluded that eating more saturated fat may not increase your risk of heart disease. Experts are still squabbling over the findings, but it goes to prove that the “eat no fat” mantra of days past is definitely changing. “Fats perform an incredibly diverse series of biochemical and physiological roles,” says cardiologist Mike Fenster, MD, author of The Fallacy of the Calorie: Why the Modern Western Diet Is Killing Us and How to Stop It. “Indeed, life is impossible without them and the consumption of certain types is a prerequisite for continued existence. Yet because the past colors our view of the present, they are often demonized and simply viewed as the cause of weight gain because they are nature’s most potent fuel.”
In one 2015 American Heart Journal study, eating three eggs a day had no adverse effects of people who had already been diagnosed with coronary artery disease. Study author David Katz, MD, MPH, director of the Yale-Griffin Prevention Research Center, also points out that in previous studies, daily egg consumption didn’t pose any harm to healthy adults or to those with high cholesterol levels but no heart disease. Meanwhile, cutting yolks from our diet in the name of health caused U.S. adults to become marginally deficient in choline, which is necessary to promote energy metabolism and cell health, Kleiner says. This year, the Dietary Guidelines Advisory Committee even advised dropping previous recommendations for Americans to reduce their cholesterol intake.
In fact, the body can’t absorb most of the cholesterol you eat, says Alexandra Sowa, MD, a clinical instructor of medicine at Weill Cornell Medical College in New York City. That means that the vast majority of the cholesterol in your body, about three-fourths of it, is produced by the liver. Why bother? Because your body needs cholesterol to form cell membranes and vitamins, she says. It’s when your liver churns out too much cholesterol that you increase your levels of blood cholesterol and your risk of heart disease. That’s often due to genetics or, as researchers are now starting to suspect, eating too many refined carbohydrates and sugar.
The Real Reason We’re Heavier—and Unhealthier—Than Ever
Since experts first started hammering down on fat and cholesterol in the late 1970s, more Americans have followed a low-fat, low-cholesterol diet. Still, Americans are more overweight than ever, says Donald K. Layman, PhD, professor emeritus of food science and human nutrition at the University of Illinois. According to the Centers for Disease Control and Prevention, more than one-third of U.S. adults are obese and heart disease is now the leading cause of death.
One reason is that people didn’t replace their fat with fruits and veggies. They replaced them with refined, simple carbs—white bread, white pasta, sugary cereals, carb-rich snack foods, and tons and tons of sugar, explains epidemiologist Deirdre Tobias, ScD, lead author of a 2015 Harvard meta-analysis that found that low-fat diets don’t do a lot for weight loss. Many of these processed, packaged low- or no-fat foods actually contained more carbs and sugar than their full-fat counterparts. After all, when food manufacturers removed fat from foods, they had to replace it with something to keep it from tasting like cardboard.
Eating refined carbohydrates in excess, however, triggers the body to release insulin, which—apart from increasing your risk of weight gain—increases the levels of fat and cholesterol in your bloodstream, Layman says.
Want to Lose Weight and Protect Your Heart? Here’s What to Eat
While experts generally agree—at least for now—that it’s best to get the bulk of your fats from unsaturated sources like plants and fatty fish, the line between “good” and “bad” fats is blurring. (Trans fats from processed foods, however, are still bad news bears.)
Experts advise that instead of getting hung up on the “perfect” macronutrient split or grams of carbs or fat per day, simply pay attention to the foods you eat. “You can eat a very unhealthy diet on a low-fat or a low-carbohydrate diet if you’re reaching for refined, processed foods,” Tobias says. Fenster recommends avoiding what he calls the “four P’s of the modern dietary apocalypse”: prepackaged, pre-prepared, (over)processed and (artificially)preserved foods. Instead, focus on whole, unprocessed foods—whether that means whole grains and bananas or avocados and eggs—and you’ll be doing both your waistline and heart a favor.