As kids head back to school, many fear that a lack of physical activity and unhealthful school lunches will contribute to the country’s obesity epidemic. A recent study, however, found that the rate of weight gain among young children is higher in the summer than during the school year. The researchers’ conclusion – parents have at least as much responsibility as schools – is common sense but takes away a convenient excuse.

Researchers at Ohio State University and Indiana University measured increases in students’ body mass index during kindergarten, the summer and first grade. They found that growth in body mass index was generally faster during the summer.

Doug Downey, a sociologist at Ohio State, told The Associated Press that for many children summer too often means watching TV, playing video games and eating unhealthful snacks.

Twenty states, including Maine, have passed laws limiting or banning soda sales in schools, enacting nutrition requirements for lunches and requiring more exercise at school.

Still, 20 percent of U.S. children are now considered obese and millions more are overweight. These children are at risk of remaining obese as adults, increasing their likelihood of developing diabetes, high blood pressure, heart disease and other chronic health problems. Not only can these problems shorten their lives, they increase health care expenditures.

Getting the message about the importance of exercise and a healthful diet to parents is more difficult than reaching schoolchildren, who spend their days in one place, leading to the focus on schools.

Convincing parents of the importance of diet and exercise is the aim of a campaign by the Maine Center for Public Health, which focused on a straightforward way to improve youth health. It’s called the 5-2-1-0 countdown to good health. Here’s what it stands for. Eat at least five servings of fruits and vegetables on most days. Limit screen time to two hours or less daily. Participate in at least one hour or more of physical activity every day. The 0 is for avoiding soda and sugar-sweetened drinks and limiting fruit juice in favor of water and fat-free milk.

The 5-2-1-0 message is reinforced by questionnaires that are now being used in medical practices across the state. The questionnaire, which asks about family eating habits, TV watching and physical activity, is meant to give physicians an easy way to start a conversation with parents about their children’s health.

Ensuring schools serve healthful food and set aside time daily for outside play is important. Extending this throughout the year would be even better.