Experts Weigh In: Will Trans Fat Bans Affect Obesity Trends?

The small town of Tiburon, Calif., initiated a nationwide wave of action when its restaurateurs voluntarily stopped using foods containing trans fats. The wave crossed the nation and broke over New York City when, in December 2006, its Board of Health approved a ban on restaurant foods containing >0.5 g of trans fat per serving. Now other U.S. cities and states are considering similar proposals.¹

Meir Stampfer, MD, DrPH, professor of epidemiology and nutrition at Harvard School of Public Health in Boston, applauds these developments. “My colleagues and I from the Harvard School of Public Health estimate, from laboratory and epidemiological studies, that between 72,000 and 228,000 heart attacks could be prevented each year in America if industrially produced trans fats were eliminated from our diet,” Stampfer says.²

Trans fats are partially hydrogenated oils commonly used for frying foods, to prolong shelf life in prepackaged foods, and in the manufacture of margarines and shortenings. Trans fats also raise LDL cholesterol, lower HDL cholesterol, and may increase risk of sudden death and diabetes, explains Stampfer. “Replacing trans fats with healthy fats will almost certainly prevent many thousands of premature deaths each year,” concurs Walter C. Willett, MD, DrPH, chair of the department of nutrition at Harvard School of Public Health.

And, Willett says, “There is now strongly suggestive information from both epidemiological and animal studies that these changes in type of fat will have a beneficial effect on obesity rates.”

TRANS FATS AND WAIST/WEIGHT GAIN

Research suggesting that trans fats carry the additional risk of increasing abdominal fat and body weight is an emerging area of study:

1. A look at the 9-year waist circumference gain among >16,000 participants in the Health Professionals Follow-up Study showed that “a 2% increment in energy intake from trans fats, isocalorically substituted for either polyunsaturated fats or carbohydrates, was associated with a 0.77-cm waist gain in multivariate analyses.”³

2. In an evaluation of male monkeys fed identical calorie amounts in diets designed to mimic the Western-style diets of humans, 35% of the monkeys' daily calories were supplied from either trans fat or trans fat-free oils. Over a 5-year period, monkeys fed trans fats showed a 7.2% increase in body weight compared with a 1.8% increase among those fed trans fat-free diets.⁴ Computed tomography measurements in selected monkeys showed significant abdominal fat deposits in the monkeys fed trans fats.⁵

3. In a Nurses' Health Study analysis of consumed unsaturated, saturated, and trans fats and weight gain over 8 years, researchers associated a weight gain of 1.7 lb with every 1% increase in percent of calories from trans fat. Of the fat subtypes assessed, trans fat had the greatest association with weight gain.⁶

But at this point, “the data are inadequate” to determine if a definitive link exists between trans fat intake and weight gain, contends Tufts University's Alice Lichtenstein, DSc.

As Gershoff professor of nutrition science at Tufts' Friedman School of Nutrition Science and Policy and director of Tufts' Cardiovascular Nutrition Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging in Boston, Lichtenstein agrees that decreasing intake of trans fats “is a move in the right direction,” and that any measure to encourage the phaseout of these fats without increasing intake of saturated fats “is probably a good idea.”

But, she notes, even if research definitively identifies trans fat intake as contributory to weight gain, “we would be misguided to assume this would solve our obesity epidemic.”

CALORIE FOR CALORIE, FAT IS FAT

Weight control goes beyond trans fat consumption; it requires attention to calorie intake, portion size, and increased physical activity. “If you sit down and eat the whole basket of bread before your meal begins,” notes American Dietetic Association spokesperson Bonnie Taub-Dix, AM, RD, CDN, “this will contribute to obesity even if there is not a gram of fat in that bread.”

Patients need to understand that foods listed as trans fat-free may not be fat-free. Substituting saturated fat for trans fat, she adds, “does not necessarily make for a healthy product.” Nor does it cut that food's overall calories.

Assessing the fat content of a meal, with the aim of limiting fats and overall calories, is a valuable dietary practice. Taub-Dix suggests avoiding crackers, instant soups, donuts, muffins, cakes, mixes, and frozen foods that may contain trans fats and pack a high caloric punch. She tells patients to order restaurant dishes prepared with healthier fats and more fruits and vegetables—especially those prepared as close to their natural state as possible—and to ask for any high-fat, high-calorie sauces to be served on the side.

“I've been in practice for over 30 years,” recalls Taub-Dix, “and I've never had a patient come to me because they were overweight from eating too many vegetables.”

CALORIC LABELING

An important move that has not garnered enough media attention is New York City's March 1, 2007, requirement that restaurants with standard menu items list calorie information at the point of purchase, says Lichtenstein. Arizona, California, Connecticut, Illinois, and New Jersey are among the states currently considering similar requirements for national chain restaurants.¹

Customers at McDonald's, for instance, may opt for small rather than large fries if they see it saves them 290 calories. Or they may pass on the 32 oz chocolate triple-thick shake when they find it packs a walloping 1,160 calories. A McDonald's Caesar salad contains just 90 calories, but adding crispy chicken ups the count to 300 calories and dousing the lettuce with creamy Caesar dressing heaps on an additional 190 calories.⁷

Whether these caloric labeling requirements will affect consumers' ordering patterns or influence obesity trends in the U.S. “is still the $64,000 question,” Lichtenstein remarks, but such labeling “is unlikely to have an adverse effect.”

Obesity comes from “people eating too much food and burning too few calories,” Lichtenstein emphasizes, and she warns that an exclusive focus on nutritional “hot items”—such as trans fats—sometimes can overshadow this reality. ▪