Are some fats more filling?

From San Diego, at the Experimental Biology 2000 meeting

If hunger returns a few hours after downing a major meal, it may be time to reach for a different cooking oil. A new study finds that when scientists substituted monounsaturated cooking oil for polyunsaturated fats, diners felt full longer.

S.E. Specter of Pennsylvania State University in State College and his French colleagues recruited 12 healthy young Parisian men into the study. Once a week for 4 weeks, they served the volunteers identical breakfasts, followed a few hours later by a lunch of chopped steak, bread, cheese, an apple, and a starchy side dish.

During two of the weeks, rice served as the side dish. On the others, the men got mashed potatoes. Each week, the researchers also varied the recipes for that starchy fare, adding 48 grams of a high-mono oil, such as canola, to every 100 g of rice or potatoes one time, and the same quantity of polyunsaturated oil, such as corn, the next. Once every hour after lunching, the volunteers rated their desire to eat.

During the first 4 hours, the men invariably felt hungrier if they had eaten rice instead of potatoes. Blood samples showed higher concentrations of sugar after meals when the men ate potatoes. This suggests, Specter explains, that although the potato was being digested faster, it remained more filling.

Over the next 4 hours, the fats’ influence emerged. The men consistently proved less hungry on the days they had eaten a high-mono oil. Yet even then, their hourly hunger ratings were somewhat lower on the days they ate potatoes.

The data “are too preliminary to warrant anybody changing their diet,” Specter cautions. However, he does wonder whether fat calories from monounsaturates might reduce people’s desire for snacks.

Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.