San Diego, Calif. -- In a recent study, young men who ate a lunch including mashed potatoes prepared with heart healthy mono unsaturated oil stayed satiated longer than when they ate the same lunch with either rice or mashed potatoes prepared with polyunsaturated oil.
"Rice prepared with polyunsaturated oil was the least effective in delaying the return to hunger over an eight-hour test period," says Dr. S. E. Specter, Penn State assistant professor of nutrition and first author of the international research team’s report.
"Speaking practically, these preliminary data suggest that the type of oil you cook with may affect satiety," he adds. "Our study indicates that mono unsaturated oils, which other researchers have shown can help lower cardiovascular disease risk, could also be important in helping control appetite."
The study was conducted in Paris, France, at the Hτtel Dieu hospital when Specter held a postdoctoral appointment there before joining the Penn State faculty. No other controlled studies have simultaneously varied the type of dietary fat and carbohydrate in normal, balanced meals to examine the time-course of the return of hunger.
Specter presented the findings for the first time in a poster, today (April 16) at the Experimental Biology 2000 conference in San Diego, Calif. His co-authors include Dr. Bernard Guy Grand, head of the departments of nutrition and internal medicine at Hτtel Dieu, J-L. Joannic, S. Auboiron, J. Raison, M. Champs, A. Basdevant, and F.R.J. Bornet.
Twelve healthy, normal-weight men, about 24 years of age, took part in the study. On one day a week for each of four weeks, they ate breakfast and lunch at the hospital. For lunch they were served chopped steak, French bread, a side dish of either mashed potatoes or rice, a piece of cheese and an apple. The mashed potatoes and rice were prepared with either a high mono unsaturated oil mixture (60 percent sunflower and 40 percent soybean), or a high polyunsaturated oil mixture (70 percent sunflower and 30 percent rapeseed).
Specter says that during the first four hours after the lunch, the men reported being hungrier if they had eaten rice no matter what kind of oil had been used in its preparation. He notes that this effect may be related to rice’s glycemic index, a measure of the magnitude and duration of its effect on blood sugar levels. Rice has a lower glycemic index than potatoes.
During the second four-hour period after lunch, the effect of the oils became apparent. When the men’s meal contained either mashed potatoes or rice prepared with mono unsaturated oil, they were less hungry four to eight hours after eating than when fed the same starches prepared with polyunsaturated oil. The effect was most pronounced, however, when the men ate the mashed potatoes prepared with the mono unsaturated oil suggesting that the two foods are working together.
The Penn State researcher says that these results support the idea that the type of fat a person eats could make a difference in how hungry they feel later in the day. "A person who eats foods high in mono versus poly unsaturated fats at lunchtime might conceivably eat fewer calories, for example, in snacks, at the end of the afternoon, " he adds.
From an appetite control standpoint, the data suggest that all calories from fat may not be the same and all calories from starch may not be the same. "In addition to the increasing evidence of their role in lowering risk factors for certain chronic diseases, mono unsaturated oils may influence subsequent hunger, suggesting a potential benefit in weight control when incorporated into everyday or therapeutic diets," Specter says.
However, the College of Health and Human Development faculty member cautions that the physiological signals that lead to meal termination or inhibit intake until the next meal are complex. He adds, "There is a need for further studies in which researchers look at different types of fats and oils in the context of a meal instead of just fat versus carbohydrates."
The research was supported by a grant from the Nutrition Health Service of Eridania Beghin-Say Corp. of Belgium.
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