In the resource-rich United States, children are more likely to be overfed and undernourished than starving and skinny. But not commonly understood is that obesity can also be the result of poor nutrition.

According to the U.S. Department of Health and Human Services (the agency responsible for devising the annual dietary guidelines) there are four nutrients of concern for people over the age of two: calcium, potassium, vitamin D, and fiber—all of which are necessary for proper growth and development. Here's a brief synopsis of what each nutrient does and why getting sufficient amounts in the diet are important:

  • The body needs calcium, a mineral, to build and maintain strong bones and move muscles. Nerves in the body also rely on calcium to carry messages between the brain and every body part.

  • Potassium keeps the heart beating with regularity and is also involved with nerve function and muscle control. In addition, potassium regulates the flow of fluids through the kidneys and new evidence suggests it may have a role in decreasing blood pressure.

  • Vitamin D is essential for bone and joint growth and strength. Insufficient amounts of the nutrient cause rickets in children and brittle bones in adults. The immune system uses Vitamin D to fight off invading bacteria and viruses. Although a healthy dose of sunshine gives your body Vitamin D, this fat-soluble nutrient must be added to low-fat milk and dairy products.

  • Fiber is important for digestion and helps guard against diabetes and heart disease, yet no one seems to be getting enough. Furthermore, high-fiber diets reduce overall calorie intake and aid in maintaining a healthy weight.

Getting Kids to Eat Nutritious Foods

Angela Lemond, RD, spokesperson for the Academy of Nutrition and Dietetics and the mother of two young children says feeding your child a diet that contains a variety of foods from each of the five food groups (grains, meats, fruits, vegetables, and dairy) is a good way to ensure they are properly nourished.

Parents of picky eaters—kids who turn their noses up at entire categories of food—often worry their poor eating habits may be harming their health.

"Kids are notorious picky eaters," says Lemond. "My 5-year-old son is tough. Evan's food preferences are milk, yogurt, cheese, bread/bagels and fruit. And when it comes to challenging the repeated exposure rule on food acceptance-he's a real champ," she says of her own parenting experience.

But she urges parents to keep trying. "Persistence does pays off...eventually," she says. "After two years of unsuccessful attempts, Evan finally eats and enjoys salmon—a really nutritious food and wonderful source of calcium."

Read on for some kid-pleasing ways to get more vitamin D, calcium, potassium and fiber into your child's diet.

Do Dairy.

Children ages 9 and older don't get enough dairy and Lemond says the anti-dairy movement is partially to blame. "There's a decent amount of people out there that are against milk," she says. However, low dairy consumption is also a problem in certain ethnic groups and those who are lactose-intolerant.

"For people who are lactose intolerant, lactose-free milk is best, but soy milk is another good alternative since it has a comparable amount of protein," say Lemond. But all milk is not created equal, adding that almond or hemp milk has far less protein per serving.

Be sure your kids are drinking milk with meals. (Whole milk is recommended for kids under two; low-fat or non-fat for older children.) If your child doesn't naturally gravitate toward milk, adding a small scoop of chocolate to make it taste better to them is fine, says Lemond. "The nutritional value of milk is so high even if you add sugar, it's still one of the healthiest beverages you can serve."

Calling all ears.

Another food people commonly consider a no-no is corn. Not necessarily because of GMOs (though if you're concerned about GMOs, buy organic corn), but rather because it's a starchy vegetable. However, it's got fiber and kids love it, says Lemond. She says it's a great way to get fiber into kids' diets but cautions parents against increasing fiber all at once. "Don't increase fiber without increasing fluid intake or your child will become painfully constipated. Liquids are necessary to move it all through."

Other good sources of fiber include: beans, oatmeal, whole-grain pasta, rye and barley. "There are lots of great cereals and high-fiber snacks like granola bars out there. Look for products containing at least 3 grams of fiber per serving to help meet the daily recommendations."

Play with your food.

Calcium starts to become an issue around the age of 9 as kids start turning to sports beverages and juice in place of milk, claims Lemond. "But other calcium-rich foods include green vegetables such as broccoli, kale and spinach." If your child isn't a veggie lover, try involving them in the cooking process. "Serving kale chips might seem really weird to a child but if you present it as a food experiment and let them help you prepare it, they might have a different attitude."

Let them eat potatoes.

Most people don't think of potatoes a health food. But guess what? A single baked potato (with the skin on) can deliver 1,000 mg of potassium-more than twice that of a single banana. Sure, you might expect them to have minerals-seeing as they spend most of their life underground-but they also have fiber (two grams) and protein (three grams). So, bring on those spuds! French fries are fine but be sure they're baked (rather than fried) to keep the calorie count in check.

Other kid-friendly sources of potassium include: strawberries, blueberries, peaches, raisins, soy beans-especially when served straight from the pod (what snack is more fun than edamame?)-and tomato sauce too!

Still worried your child isn't eating well? Proper nutrition is best reflected on the pediatrician's growth curve. "If your child is well nourished he or she should be growing at a normal rate," says Lemond. Get more of her nutrition advice.

Angela Lemond, RD, reviewed this article.