"While many people will only focus on the fat content of a particular food, it is important to examine how that food influences the consumption of companion foods," said Brian Wansink, a professor of marketing and nutritional sciences.
As an example, olive oil has been widely touted as a healthy alternative to butter. But if people consume too much olive oil, its beneficial effects can be negated, Wansink said.
To find out if this happens in real life, Wansink observed the eating habits of 341 diners at two Italian restaurants over a succession of nights. The results of his study are being published in the July issue of the International Journal of Obesity.
When diners arrived at each restaurant, they were provided with either a dish of 66 grams of olive oil or half a stick (66 grams) of soft block butter next to their plates. Six pieces of machine-cut Italian bread were given to each diner. After the meals were finished, Wansink and his student assistants weighed the butter or olive oil remaining, along with the bread and any plate waste.
Wansink found that diners who were given olive oil consumed more oil on each piece of bread than those given butter. This resulted in 44 calories of fat per slice of bread with olive oil compared with 33 calories of fat for bread and butter.
Even though the fat in olive oil is widely regarded as more healthy than the fat in butter, "fat is still bad for Americans," Wansink said, "and consuming that much olive oil can trade off some of its benefits as a substitute for butter."
One of the problems with olive oil is that "as a liquid product, it is hard to control how much you actually use as compared to butter that is spread on with a knife."
Many diners reported that bread dipped in olive oil was "more filling."
A related finding was that nearly all of those queried in exit interviews underestimated how much bread they actually ate. "This underestimation tendency is a consistent and well-documented phenomenon in consumption research, often occurring because most adults simply do not monitor their consumption and are unaware of the forces that influence them," Wansink wrote in his forthcoming article.
As opposed to traditional dietary recommendations, Wansink suggests that people spend less time obsessing over the specific fat content of a single item and spend more time observing their total food selection and intake, especially of rich toppings and spreads. His journal article is titled, "Interactions Between Forms of Fat Consumption and Restaurant Bread Consumption."
Journal
International Journal of Obesity