(CNN) -- Introducing healthy habits early can make a big difference on your toddler's health later in life. According to a study published in the New England Journal of Medicine, a big part of a child's obesity risk is established by age 5.
But what does "healthy" really look like for a 2- to 5-year-old child? Should you be counting calories or hitting the gym(boree)? And if your kid is a picky eater -- as most are -- how can you ensure they're getting the essential nutrients?
A recent study published in JAMA, the journal of the American Medical Association, found obesity rates among children 2 to 5 years old decreased 43% between 2003-2004 and 2011-2012, while most other age groups saw little to no decline. The decline may be due to young parents who are becoming more educated about the risks of childhood obesity and are actively looking to prevent it, said Wendy Palmer, a registered dietitian at Children's Healthcare of Atlanta.
The first thing parents should know is whether their children are currently at a healthy weight, Palmer said. Obesity can be hard to gauge in young kids.
"You might look at a child and think there's not a weight problem at all, or you might think there is and there's not," she said.
Palmer says body mass index, or BMI, is the best indicator of a child's weight status. The Centers for Disease Control and Prevention defines childhood obesity as "a BMI at or above the 95th percentile for children of the same age and sex."
Parents can measure their children's BMI at home using various online tools.
While BMI is a helpful number, it's also important to focus on a child's growth pattern, Palmer says. Some children are consistently bigger and heavier than others and may still be healthy. But when children are getting heavier over time, it can be an early warning sign of a weight issue.
Parents are essential to helping children learn to make healthy lifestyle choices. With kids, the focus should be on providing a balance of nutrients.
"You hear a lot about calories," Palmer said. "For kids these ages, it's not about calories, it's more about them having a wide variety of foods."
Get kids started eating regular, healthy meals. We all know breakfast is important -- and it could be even more so down the road. A 2013 study by the Arkansas Children's Nutrition Center found children who ate breakfast used less mental effort to solve math problems and scored higher on tests than students who did not eat breakfast.
Children's Healthcare of Atlanta recommends following the MyPlate guidelines outlined by the USDA, which suggest filling half of every plate with fruits and vegetables and dividing the other half between whole grains and lean protein.
Palmer said following the MyPlate guidelines can be tricky with children, especially when preparing breakfast. She recommends including a protein source. For example, a healthy breakfast for your toddler might be whole wheat toast, eggs and a glass of low-fat milk.
For pickier eaters, making food visually appealing will help, said childhood obesity expert and registered dietitian Melissa Halas-Liang.
"If the food is presented in a colorful, attractive way that a young kid can pick it up easily ... they're more likely to enjoy and eat that food," she said.
So take that slice of whole wheat toast, spread it with nut butter for protein, and garnish it with sliced fruit in the shape of a smiley face.
Some children may never grow to like breakfast food, Halas-Liang says, so parents may have to make other healthy foods their child enjoys, such as brown rice fried with olive oil, an egg and assorted vegetables and serve them for breakfast.
Getting young children excited about food by making it fun and offering a variety of tastes, colors, shapes, textures and temperatures can help them eat better at all meals, Halas-Liang says. Children who regularly reject meals should be actively involved in helping pick and cook them.
Palmer says a healthy, nutrient-filled diet works best to combat obesity when in conjunction with regular exercise.
Two- to 5 -year-olds should be getting around 60 minutes of exercise every day, Palmer says. But that doesn't have to be all at once -- it could be broken up throughout the day. For young children, it's less about exercise and more about moving their bodies, she says, so active play is usually enough.
It's important for parents to play along with their children, rather than force them into it, Palmer says. Parents who present active play as fun and participate in the games with their children are more successful at getting them moving and engaged.