New research out of the University of Chicago suggests that eating foods labeled as "healthy" makes some people hungrier (and eat more!) than eating foods labeled as "tasty" or not eating at all. Thus, researchers suggest that if you're trying to encourage a family member to lose weight it's best not to focus on the healthfulness of the foods you serve.
A series of studies were performed to examine how imposed healthy eating influenced individuals' experienced hunger. In one study, research subjects were all given the same protein bar and told their job was to taste a food that was described as either healthy or tasty (imposed conditions) or to choose between the bars (free-choice conditions). Then, they rated their hunger. Subjects that were given the bar described as healthy said they were hungrier after eating it than those who were given the same bar described as tasty or those who freely chose their bar. In another study, subjects were given the same piece of bread that was described as healthy or tasty. In addition, they were asked how much they valued watching their weight. As in the previous study, subjects given the bread described as healthy rated they were hungrier and consumed more of an available snack than those given the bread described as tasty. But, this wasn't true among the subjects who valued watching their weight. Instead, they felt that they chose to eat the healthy bread.
Study authors explain that while people eat to fulfill their appetite, another major goal people have when selecting food is to maintain good health. But, these are conflicting motives - eat to get full or choose less (or lower calorie) food to be healthy. In people trying to be healthy or lose weight, the "maintaining good health" goal is strengthened when they eat a food described as healthy when freely chosen and often even when imposed. However, imposed healthy eating in those not committed to health/weight loss believe that the health goal is sufficiently met after they eat a food described as healthy, increasing the strength of the conflicting motive to fulfill their appetite.
Take away message: Encouraging healthy eating is a lot more complex than telling someone what to eat or even serving someone healthy foods. People who are not committed to eating healthfully need to feel that they have made the choice to eat the healthy food. Therefore, let them make the choice by offering a variety of foods including tasty healthy foods and don't emphasize the healthfulness of the foods you serve.
Finkelstein, S. (2010). When Healthy foods make you hungry. Journal of Consumer Research, Retrieved from http://www.journals.uchicago.edu/doi/abs/10.1086/652248 doi: 10.1086/652248.