Another Way Saturated Fats Can Hike Heart Risks

Physicians and health columnists have been exhorting the public for years to pare saturated fats from the diet. Numerous studies have linked heavy consumption of these fats to elevated cholesterol, a major risk factor for heart disease. Now, Johns Hopkins University researchers tie high-saturated-fat diets to a second risk factor for cardiovascular disease: abdominal fat.

The saturated fat in burgers and in potatoes fried in beef tallow or lard encourages the body to put on pounds around the waist. However, many restaurants now fry potatoes in vegetable oils. These oils, rich in polyunsatured fats, foster excess body fat to deposit lower, around the hips. While excess fat anywhere is not good, studies have linked special health risks to fat around our middles.

A large and growing share of the U.S. population weighs more than it should. Some of these people’s bodies tend to layer most of their extra fat onto their hips, giving them a pear-shape physique. The rest store much of their excess poundage around the middle, giving them an apple shape. Nutritionists actually call these two groups “pears” and “apples.”

Several studies have linked apple-shape obesity to an especially increased risk of diabetes and heart disease. One mechanism behind both diseases appears to be the propensity of abdominal fat to trigger the production of C-reactive protein (SN: 5/1/99, p. 278). Recent investigations have correlated this biochemical indicator of inflammation with an elevated chance of developing both diabetes (SN: 8/11/01, p. 89: Available to subscribers at Inflammation linked to diabetes) and heart attacks (SN: 4/20/02, p. 244: Available to subscribers at Cardiac Culprit: Autopsies implicate C-reactive protein in fatal heart attacks).

Researchers at the Johns Hopkins University School of Medicine in Baltimore have now linked saturated-fat consumption in overweight people more with the apples than the pears. Kerry J. Stewart and his colleagues reported their findings in Chicago earlier this week, at the American College of Cardiology annual meeting.

Jidong Sung, a Johns Hopkins physician on the team, surveyed the eating habits of sedentary adults 55 and older–46 women and 38 men. “I think these people were also fairly representative of the average middle-aged person without severe chronic diseases,” observes Stewart. Though generally healthy, these moderately heavy to mildly obese individuals did suffer from mild, untreated hypertension. Indeed, that was a condition for entry into the trial, which was designed primarily to evaluate benefits of exercise on such people’s stores of body fat.

During the screening phase of that trial, the researchers used X rays to measure total body fat and magnetic resonance imaging to record visceral fat, the internal padding deep within the trunk. Apples carry more visceral fat than pears do.

Most people are concerned about the fat that’s visible, the padding beneath the skin of their faces, limbs, and trunk. However, Stewart notes, from a health perspective, “it’s really the fat they don’t see–within the abdominal cavity and wrapped around the organs–that’s an issue.”

When he and his colleagues compared the amount of this internal, shrouded fat with the participants’ detailed dietary records, they found that people who ate the largest share of saturated fat (such as palm oils or animal fats) deposited more of their fat in their abdomens–making them apples–than pears did. Pears, in fact, had a higher ratio of polyunsaturated fats (such as from corn oil) to saturated fats in their diets.

Diet wasn’t the only factor predisposing an individual to appledom or peardom–nor even the largest factor.

Total body fat explained 13 percent of an individual’s predilection to become an apple or pear–the heavier a person, the more applelike. Gender accounted for 13 percent of a person’s chance of becoming an apple or pear–with men more likely to plump into apples. In contrast, the ratio of polyunsaturated to saturated fats in the diet explained only 4 percent of the tendency to a body shape.

Four percent might not sound like much, but Stewart argues, “it could make a big difference” in contributing to health risks. Moreover, he points out that this dietary link emerged in a group of individuals who were all about equally overweight and consuming relatively similar amounts of calories. If the surveyed population had included a range of people from skinny to morbidly obese, the various dietary fats might appear more potent, he said.

The research couldn’t pin down the explanation for some 70 percent of a person’s inclination to put their extra fat in one place or another. Clearly, Stewart says, “a big part of this puzzle remains unfinished.”

For now, he says, “The take-home message is that if you’re going to stay fat, try to make more of your dietary fats polyunsaturated.”

Janet Raloff

Janet Raloff is the editor of Science News for Students, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer.

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