A Harvard University study released last month found that kids gain weight more quickly over the summer than during the school year. With the warm weather and more opportunities to play outdoors, one might think the opposite is true. But it turns out there are several factors at play.

The study, released by the Centers for Disease Control and Prevention journal Preventing Chronic Disease, compiled and analyzed the results of seven studies published since 1990. The studies were conducted among children ages 5 to 17. The researchers found that black, Hispanic and overweight children and adolescents were at highest risk of gaining weight quickly over the summer. The study determined that these adolescents gained weight because they spent more time in front of TV and computer screens and were more likely to eat unhealthy snacks. These children also may have slept less, as their summer days were less structured compared with those during the school year.

There are several basic strategies that can help keep kids from gaining weight during summer vacation. Here are five.

Even if you have a bustling work schedule, it's important to make time to get the kids outdoors. Take a family walk after dinner, play soccer in the yard or go to the local park. Finding time to make sure your child is active is half the battle.

When it’s hot outdoors, cold drinks like soda, lemonade, sports drinks, juice drinks and other calorie-heavy drinks may seem harmless. As a once-in-a-while treat, these sugar-laden drinks are okay, but kids should be sticking with good old water as their main source of fluids. Milk (nonfat or low-fat) and 100-percent fruit or vegetable juice are other choices for kids if they're not having water or seltzer.

Free of homework and other school obligations, kids can be tempted to sit on their behinds playing video games, texting and watching TV. But screen time should be limited to 2 hours a day maximum. Parents should tuck away phones and video games before bedtime and avoid letting kids have a television in their bedroom.

During the summer, routines get out of whack  -- and that includes eating routines. Try to stick with an eating schedule for breakfast, lunch and dinner, with two to three healthy snacks in between. This will help prevent mindless munching and grazing throughout the day.

Although the sun may stay out longer during the warmer months, kids still need to maintain a regular sleep schedule. A 2014 study published in the journal Pediatrics found that kids who don’t sleep enough had a higher risk of obesity. Up to the age of 12, kids should be getting about 10 to 12 hours of sleep each night. Creating a bedtime routine with your child (like taking a bath or reading a story) helps calm them down and gets them physically and psychologically ready for bed.

Toby Amidor, MS, RD, CDN, is a registered dietitian and consultant who specializes in food safety and culinary nutrition. She is the author of The Greek Yogurt Kitchen: More Than 130 Delicious, Healthy Recipes for Every Meal of the Day.