The first article in this edition of the newsletter explores the widely replicated
Why do boys eat less F&V than girls?
Today, in Western countries men die earlier than women. Men also eat less healthfully than women, e.g. they eat less fruits and vegetables (F&V). Boys also eat less F&V than girls. However, sex is not (at least not easily) changeable, and for intervention development it is important to identify modifiable determinants for the sex disparity. In a recent article, we wanted to explore why boys eat less F&V than girls1.
Only a few studies in adults have assesses this question. Suggested determinants (or reasons) for the sex disparity among adults are that men have poorer nutritional knowledge, less interest in health in general, and dieting status (women are more often dieting). In earlier Norwegian studies, a number of personal modifiable determinants of adolescents’ F&V intake have been identified, including perceived accessibility of F&V at home, modelling, intention to eat 5-aday, preferences for F&V, self-efficacy to eat 5-a-day and knowledge of recommended intake levels. In the present study, using data from the Fruits and Vegetables Make the Marks (FVMM) project, these factors were analysed as potential mediators of the sex disparity in adolescents F&V intake.
In the study sample boys clearly ate less F&V than girls: 11.9 and 14.5 times/week, respectively. Boys also scored lower on all the potential determinants (e.g. boys had less knowledge about the national F&V recommendation). The sex difference in the potential determinants explained 91% of the sex difference in F&V intake. One factor explained more than all the other together: preferences. In addition, perceived accessibility also uniquely explained some of the sex disparity. In summary, this study indicates that Norwegian boys eat less F&V than girls because they like them less, and also in part, because they don’t find them as accessible at home as girls find them to be. The sex disparity in adolescents’ F&V intake does not appear to be explained by girls’ role models greater knowledge, stronger intentions and self-efficacy.
It has previously been reported that boys like F&V less than girls. Even among four year olds, girls have been reported to like vegetables better than boys. However, the question why boys like F&V less than girls remains unanswered. It has been suggested that social desirability may have a stronger impact on girls’ responding to the questionnaire because of the greater importance that females attach to diet. A second reason might be that boys’ greater liking for more energy dense foods (i.e. not F&V) serves as an adaptive purpose for their greater energy requirement. This hypothesis points towards physiological differences between boys and girls. Could it be that boys like F&V less than girls mainly because boys and girls physiologically are different? In traditional hunter-gatherer societies, men were hunters and women were gatherers. Even if the food were divided between the sexes, men probably ate more hunted animal food and women probably ate more gathered plants. The result might be that a difference in food preferences between males and females evolved. However, this is a hypothesis that needs to be tested.
We also observed a sex difference in perceived accessibility of F&V at home, and girls scored higher than boys. However, parents within the FVMM cohort do not report the accessibility of F&V at home to be different for boys or girls. The sex difference must therefore be due to how the adolescents perceive the accessibility and not to the accessibility at home itself. Therefore part of the sex difference in F&V intake is due to the fact that girls perceive the accessibility at home to be higher, even if it probably is not true.
In conclusion, this study indicates that the main reason why boys eat less F&V than girls is because they like them less. An important next research step will be to assess why girls like F&V more than boys
- Bere E, Brug J, Klepp K-I. Why do boys eat less fruits and vegetables than girls? Public Health Nutrition. Published online ahead of print
August 1 2007