Is Fat Making a Comeback?
Not really. But experts say low-fat diets aren't the answer.
May 15, 2000 -- Don't butter your bread. Try marinara sauce instead of alfredo. Go easy on fried foods. We Americans have heard it all. And nutritionists' goading has worked. We've cut back on fat -- from 40% of calories in 1968 to only 33% today. We've also lessened the amount of saturated fat in our diets from 18% to only 11%, according to the U.S. Department of Agriculture. By all rights, we should be throwing a party for ourselves, complete with low-fat chips and a piece of fat-free cake for everyone.
But just when it seems like it's time to break out the noisemakers, naysayers have crashed the party, warning that low-fat diets aren't a good idea for everyone. Some of the country's leading diet and health experts, in fact, now say that a low-fat, high-carbohydrate diet -- precisely the diet recommended by the American Heart Association -- could actually increase your risk of getting coronary heart disease rather than decrease it.
The Lowdown on Low-Fat Diets
It's easy to understand why experts might have first begun recommending low-fat, high-carbohydrate diets. Gram for gram, fat contains more than twice the number of calories as carbohydrates. Cutting back on the amount of total fat in the diet and replacing it with carbs would seem to be a great way to lose weight.
Fat, in its saturated form, can also raise cholesterol in the blood, which increases your risk for heart disease. "Cut back on total fat, the thinking went, and you'll cut back on saturated fat," says Marion Nestle, PhD, head of New York University's food sciences department.
But cutting back on fat hasn't worked as well as was first hoped when it comes to helping us lose weight. While products like low-fat crackers and nonfat cakes have crowded grocery store shelves, Americans have continued getting fatter and fatter. The reason: Although we're eating less fat, we're consuming even more calories than ever, feasting on sugars and highly refined flour -- otherwise known as simple carbohydrates.
It's not just looking sexy in a bathing suit that's at stake, either. There's another, more serious reason to question the merits of a low-fat, high-carb diet: While such an approach reduces artery-clogging LDL cholesterol, the low-fat, high-carb diet also lowers another form of cholesterol known as HDL. Sometimes called "good" cholesterol, HDL has been shown to remove "bad" LDL cholesterol from the bloodstream.
"When HDL levels fall, heart disease risk climbs, even if your total cholesterol remains normal," says Frank Sacks, MD, a leading epidemiologist at the Harvard School of Public Health. A low-fat, high-carbohydrate diet also raises the level of triglycerides -- fat molecules in the bloodstream that are a marker for increased heart disease risk.
A far healthier diet, Sacks and others believe, is one rich in unsaturated fats, which are found in vegetable oils, nuts, seeds, and grains. On a relatively high-fat diet -- as long as the fats are unsaturated -- levels of bad cholesterol fall while levels of good cholesterol remain high, studies show. Triglycerides also stay low. Sacks, who is also a heart specialist, believes a heart-healthy diet can contain up to 40% of its calories from fat, as long as most of the fat is unsaturated.
The Debate Heats Up
Three years ago, in the pages of the August 21, 1997 issue of the New England Journal of Medicine, experts on both sides of the diet debate squared off.
Proponents of low-fat diets acknowledged that cutting way back on fat can lower HDLs and raise triglycerides. But they insist that these changes have only been shown to pose trouble for people who eat the average American diet, which gets one-third of its calories from fat.
Dean Ornish, MD, a researcher at the University of California at Berkeley who was one of dozens of researchers to take part in the debate, points out that if there's very little fat in the diet, you don't need all that HDL cholesterol in the first place. In studies published in the December 16, 1998 issue of The Journal of the American Medical Association, Ornish showed that a very low-fat diet can reduce cholesterol buildup in the arteries and lower the risk of heart attack.
Ornish advocates a diet with no more than 15% of its calories from fat. William Connor, MD, a nutrition professor at Oregon Health Sciences University in Portland is more moderate, saying that the ideal diet should derive between 20% and 25% of its calories from fat.
It Depends on You
Experts are still arguing over the relative merits of low- vs. higher-fat diets. But by now, the two sides have also carved out some common ground. The best diet depends, it seems, on who you are.