Is Fat Making a Comeback? (cont.)
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.