Sometimes the hardest thing to do as a parent is to say nothing. You can’t say “you’re too fat.” You can’t say “did you eat the whole bag?” You can’t say, “why aren’t you outside?”

But that may be the best way to help your kids lose weight or stay at a healthy weight. Mary Story, an epidemiologist at the University of Minnesota, is an expert on adolescent obesity. She and her colleagues at the university have been running a research study called Project Eat for years. They’ve been following kids from pre-adolescence through teenage-hood and into young adulthood, surveying them and their families along the way. They are getting a handle on what works and what doesn’t.

 They know that if rising adolescent obesity rates have slowed down, as researchers reported yesterday, it’s because parents had a hand in it.

  ”What drives obesity are two things. Its food. And how they are moving their bodies,” she said.  

But it’s what parents don’t say — and what they do — that’s most important, she said. Eating regular family dinners is a big help, especially for girls, they found. So is taking the TV out of their bedrooms.

Don’t focus on their weight. Don’t focus on losing weight, she said. Instead, as long as you’re the one buying the groceries, focus on buying more fruit and vegetables and less junk. As long as you are the one making meals, make the portions a little smaller.

Entice them away from the computer and the TV. Do something with them that involves moving your bodies, and do that everyday. Too much? Okay then, four or five times a week.  ”Be a role model,” Story said. 

That’s a lot harder.

 What’s worked for you and your kids? Do you have any ideas to share about how you stopped the obesity epidemic in your family?

Once again a huge study comes out that says it’s what you eat (or don’t eat) that matters. Monday the Archives of Internal Medicine published a study of more than 88,000 women who were tracked for almost 25 years. The ones who ate closest to the DASH diet — one high in fruits, vegetables, whole grains, low fat dairy, and low in red and processed meats had a 24 percent lower risk of heart attack. And they had an 18 percent lower risk of stroke.

In short, “eat food. Not too much. Mostly plants.” Those words, by the author Michael Pollan (here’s his website), are the best summary of a good diet that I’ve ever read. Now, he went on to use a lot more words (not too many) in his most recent book “In Defense of Food.” But this is basically what he meant by that short formula:

Eat food means eat only things that your grandmother would have eaten. That means minimally processed food that’s a close to it’s original form as possible. That way you avoid all the calories, fats and additives that the food industry puts in processed food to make them taste better.

(Forgive my peeve moment here: It annoys me that the Food and Drug Administration does not require manufacturers to list the sugar they add to a product separately from the sugar that occurs naturally in the food. Fruit juice, for example, often contains both natural and added sugars. Which is which? They don’t tell us.)

Not too much means a calorie is a calorie is a calorie whether it comes from broccoli or a Pop Tart. So don’t consume more than you need. (Yes, I know, easier said than done.)

Mostly plants means just that. It means eat less meat and the stuff that comes from animals, like cheese and milk products.

That in essence is the DASH diet. ( Here are some guidelines and recipes from the National Institutes of Health.) Women who followed it had lower blood pressure, and fewer heart attacks and strokes. It also turns out, as always, that diet isn’t everything. The researchers found that the women who ate a DASH diet also exercised more, smoked less, ate fewer calories, and were more likely to take multivitamins.

But the next time you or those you love get confused about what to eat, just remember: Eat food. Not too much. Mostly plants.

And enjoy.