If you'd like a glimpse into your child's future, you don't need a magic mirror. You just need to see who he or she is eating with.

It turns out those eating buddies play a direct role in how much your kids munch – and they're not exactly good influences.

I'm already greatly concerned by the eating habits of our children. American kids in general suffer from some pretty serious nutritional deficiencies, and a study in the latest issue of the Journal of Clinical Nutrition shows that those bad habits are contagious.

It found that children with friends who eat too much are likely to do the same.

While it's nice to know that your kids are learning to share, bad eating habits are the one thing you don't want your child picking up from friends.

Researchers allowed 130 kids between the ages of 9 and 15 to eat as much as they wanted while in certain scenarios, with friends and strangers of different weights. They found that kids ate more when with friends, which makes sense. But they also found that kids ate even more – a lot more – when with overweight friends.

And the worst match-up of all was an overweight kid with an overweight friend. These kids were likely to eat up to 300 calories more when with each other than they would with a thin friend.

While I don't like to take a fatalistic approach when it comes to health, your weight IS within your control — if you're willing to discipline yourself. The numbers don't lie. I remember a Harvard study from 2007 that found that adults are 57 percent more likely to become obese if a friend does. Our odds of getting fat also go up by 40 percent if a sibling becomes obese, and 37 percent if a spouse does.

So if your pack of friends is starting to resemble cows rather than wolves, maybe it's in your interest to stray from the herd a bit – or at least keep a closer eye on your waistline and take charge of your eating habits.

And when it comes to your kids, you're better off trying to take charge of their eating habits rather than choosing their friends for them. There's one simple way to do that: Start making their lunches for them.

Sure, they might issue the standard complaints at first. But if you involve them, let them help plan and even make those healthy lunches, your kids could soon have meals that everyone at the lunch table will envy.