Don’t be surprised if you find yourself actually craving a giant kale salad after upping your exercise regimen.
In a study published last week in the Journal of American College Nutrition, researchers found that voluntarily adopting a regular exercise routine may naturally improve fruit and vegetable consumption. This occurs because of the transfer effect, wherein learning new skills, information, and attitudes in one behavior—exercising, in this case—transfers to a second behavior (eating).
Researchers used data from 6,244 respondents to the US Department of Labor’s National Longitudinal Survey of Youth 1997, which tracked the eating and exercise behaviors of people born between 1980 and 1984 at ages 18-22 and 23-27. (It also tracked their eating, but not their exercise, at ages 27-31.)
After adjusting for sex, race, education, income, and body-mass index, the researchers found a linear relationship between exercise and fruit and vegetable consumption: The more you exercise, the more produce you’ll eat.
Respondents who continued to get adequate amounts of exercise (defined as 30 minutes at least 5 time/week) at both ages also reported eating the highest amounts of fruit (6.2 times/week at ages 18-22 and 7 times/week at 23-27) and vegetables (7.4 and 8.3 times/week, respectively). And those who went from getting inadequate to adequate amounts of exercise saw the biggest increases in fruit and vegetable consumption, from 4.8 times/week to 6.2 times/week for fruit, and from 5.9 to 7.4 times/week for vegetables. The only participants to see a drop in fruit and vegetable intake were those who had a decrease in exercise levels. Those who exercised the least also ate the least fruit and vegetables.
These changes, according to the researchers, can be explained by two kinds of transfer effects. In the first, because both exercise and eating fruits and vegetables lead to the same goal—a healthy weight—individuals can easily transfer lessons from one to another. The second kind of transfer effect is the result of a person’s mental bandwidth: Once exercise becomes part of a person’s regular routine, he/she no longer needs to think about it, freeing up the brain to think about new ways to be healthy, like eating more fruits and vegetables. But, the researchers point out, the other edge of this sword is that beginning an intensive exercise program could negatively affect fruit and vegetable intake because of all the mental energy expended on the workouts.
The researchers note that the study was limited by several factors. First, they did not assess social and environmental factors considered in other studies examining the relationship between fruit and vegetable intake and exercise. Plus, their data source, because not originally intended for this use, was not as complete as they would have liked; for example, it did not include exercise data for ages 27-31.
Still, low-cost strategies to control weight can be designed by targeting just one behavior, and letting peoples’ natural tendencies do the rest.