If you're hoping to slim down, try not to focus on how healthy that low-fat, low-kilojoule salad you ate for lunch was.
People who were asked to taste food described as "healthy" reported being hungrier afterward than people who ate the same food when it was described as "tasty."
"When people feel they are required to eat healthy food, eating that food makes them hungry," said senior study author Ayelet Fishbach, a professor of behavioural science and marketing at the University of Chicago. "They are hungrier than if they didn't eat anything at all or if they'd eaten that food without thinking of its healthiness."
The study was published in the Journal of Consumer Research.
Impact of perceptions
Researchers conducted several experiments to explore the impact of perceptions about the health content of food and how full it made a person feel.
In the first experiment, researchers asked 51 college students to sample a chocolate-raspberry protein bar. Students were either told they were sampling "a new health bar," containing lots of protein, vitamins and fibre, or a "chocolate bar that is very tasty and yummy with a chocolate-raspberry core."
Later, when asked to rate their hunger, those who ate the "health" bar rated themselves as hungrier than those who ate the identical bar described as "tasty," according to the study.
A third group of students was asked to examine the bars and rate their hunger but they did not eat either bar. Their hunger levels were about the same as students who ate the bar described as "yummy" - meaning that eating the "healthy" food actually made them feel hungrier than if they hadn't eaten a bar at all, the researchers said.
Trick people into hunger
For dieters, a similar decision-making process may be involved when they choose a salad instead of a burger and fries at a restaurant, only to go home and eat a big dessert. Eating healthy foods may allow us to believe we have made progress toward health goals but trick us into thinking we are hungrier than we actually are, according to the study.
"One of the challenges in losing weight is that people tend to compensate themselves for partial success by overeating and will end up gaining that weight and more," Fishbach said.
In a second experiment, 62 participants were given a piece of bread alternately described as being low-fat and nutritious or "tasty, with a thick crust and soft centre."
After sampling the bread, participants were offered a snack of pretzels, which are considered a "neutral" food - neither healthy, like carrot sticks, nor particularly pleasurable, like chocolate.
Participants who sampled the "healthy" bread ate more pretzels afterward than those who sampled the "tasty" bread, researchers found, though those who said they were concerned about watching their weight tended to eat fewer pretzels than those who were relatively unconcerned.
Choice makes a difference
In a third study, researchers offered students a choice of chocolate-raspberry protein bar or a honey-peanut protein bar, with one randomly described as healthy and the other as tasty. When given the chance to decide for themselves if they wanted the healthy choice or the guilty pleasure, there was no difference in hunger levels afterward between the two groups.
The reason? Making the choice themselves may have meant they were more committed to eating healthfully, Fishbach said.
"When people feel obligated to eat healthy, it's making them hungry and they eat more. When they eat the same food because they have free choice, they are not going to rebound by eating a lot," Fishbach said.
Connie Diekman, director of university nutrition at Washington University in St. Louis, Mo., said the study shows that encouraging healthy eating is a lot more complex than just telling people how many servings a day of fruits and vegetables they should eat.
Healthy vs filling
"The perception that 'healthy' isn't going to meet enjoyment goals is a very strong message for all of us," Diekman said. "Healthy foods must taste good. Unfortunately, people assume they won't taste good. And even if it tastes good, their brain may be telling them otherwise."
Campaigns to encourage weight loss need to take into account the potential for healthy-food messages to backfire. "Just saying we need to eat healthy, lose weight and exercise more doesn't work unless individuals are committed to it," Diekman said.
Can simply knowing that snacking on carrot sticks now will make us crave carrot cake later help people combat their urge to indulge?
"We don't have clear evidence, but I think that knowing the info should help," Fishbach said. "I think people can train themselves to fight food temptations." - (Jenifer Goodwin/HealthDay News, April 2010)