Feeding children more nutritious meals may not make them vegetable lovers, but can promote healthier weight over time by reducing the added sugar and fat they consume, finds a Cornell-led study that implemented one of the largest-scale dietary interventions focused on young people.

Tracking nearly 300 lower-income families in the U.K. over three years, an international research team tested the effect of changes in what children and their parents ate, or how they ate, on body mass index. For 12 weeks, more than 100 families had ingredients and recipes for five nutritionist-designed meals per week delivered to their homes.

Another roughly 70 families were asked to eat three meals a day at regular times and to limit snacking—potentially a key contributor to obesity, which is more prevalent in vulnerable populations, according to the researchers. A control group did not change its diet.

Neither the “meal” nor “snack” approach affected adults’ BMI much, confirming that changing eating habits becomes harder later in life. Among children, who were between 2 and 6 when the study began, the number in higher BMI percentiles declined for both groups, but increased in the control group. Improvements were sustained over three years among the children whose families received meals, but faded after a year for those who limited snacking—a protocol participants found challenging to maintain.

The researchers believe the parents who received meal kits for three months continued to feed their children healthier diets—cutting sugar, in particular—even if they didn’t change their own habits. The results should empower parents to know they can positively influence a child’s health without imposing lots of food they don’t like, said Michèle Belot, professor in the Department of Economics.

“It’s not that the children suddenly started preferring and demanding broccoli and salads and things like that, which perhaps should not be the goal,” said Belot. “Rather, parents seem to have decided to change what they put on children’s plates, restricting a bit their access to unhealthy foods.”

Belot, who holds appointments in the ILR School and the College of Arts and Sciences, is the first author of “Changing Dietary Habits Early in Life: A Field Experiment with Low-Income Families,” published in the Journal of Political Economy: Microeconomics.

Policies have promoted healthy diets through information campaigns, taxes and sometimes “nudges” designed by behavioral economists. Most studies, however, have examined the effects of isolated purchase or eating decisions over shorter time horizons. The authors believe the new study is the first to investigate dietary interventions for young children and parents at home, and they said “the scope of the interventions tested is unprecedented.”

Belot, whose research agenda includes studying the formation of habits and preferences, finds nutrition fascinating since it involves biological processes that may drive behavior, regardless of how knowledgeable someone is about diet.

“It’s very difficult to go against things like hunger, or to have the self-control not to eat certain things one enjoys,” Belot said. “We’re interested in understanding how these tastes and preferences are developed, and can we potentially influence that process?”

The interventions built on research indicating that influencing habits early in life holds the most promise for long-term impact, and sought to make experimenting with a range of healthy foods easy and affordable for families.

The results did not match what habit models would predict, the researchers said. Three years into the study, children expressed even more interest in sweets. But parents’ food purchases did appear to change, resulting in significant BMI benefits for children—a drop of 5 percentage points in the highest BMI percentile, relative to the control group, Belot said.

The authors suggest that if they could be made affordable, subsidized meal delivery services could be an effective way to reduce childhood obesity in lower-income families living in “food deserts” that lack access to healthy food. Otherwise, Belot said, families should simply strive to limit children’s access to less-healthy food.

“The goal is to make sure that what you put on the plate is not too much a sort of junk food,” she said. “You can control the plate as a parent, and I think that’s very powerful, at the end. Because if children are hungry, they will eat.”

Study co-authors are Noémi Berlin, researcher at the Université Paris Nanterre, France; Jonathan James, senior lecturer in the Department of Economics at the University of Bath, England; and Valeria Skafida, senior lecturer in social policy at the University of Edinburgh, Scotland.