Did you think the formula for weight gain = calories eaten – calories burned? It is that easy, but some foods are especially bad because they increase your calories eaten. When it comes to calories, A recent Harvard study found that all foods aren’t created equal. Some foods make us pack on a pound per year (!)—while others keep weight off—they help us eat fewer calories. Healthy food choices can help you feel full, which is one reason they’re slimming. We You Docs believe that you should diet smart, not hard. So you should use science to help you make dieting smart, and not hard. While Mother Nature works with you, it’s not always easy to make diet decisions when you’re on-the-go and faced with endless food choices. We’re here to start you with some tips.

If you’re crazy for carbs like bread and pasta, make it 100-percent whole grain (yes, it must be the only grain ingredient listed, or if multigrain, it must be all 100-percent whole grains—food is not “Let’s Make a Deal!”). The Harvard study, which was published in the New England Journal of Medicine, showed that refined carbs like white bread and white rice are sneaky weight-boosters. Stripped of fiber, your body quickly converts these carbs to sugar. One-hundred percent whole grains stick with you longer.

When it comes to diet, potatoes are evil. It comes as no surprise that the study found that eating potato chips every day is the biggest snack no-no. But even a daily serving of boiled potatoes was correlated with packing on a pound over the year!

QUIZ: What’s Your Eating Style?

So what to snack on instead?If you add good fats to your diet, they’ll help keep you fit and full. In the study, a daily serving of nuts kept weight off. We agree. We’re crazy (OK, nuts) for nuts—especially walnuts. Walnuts have six times more omega-3s than other nuts (specifically, alpha-linolenic acid) and can lower your lousy LDL cholesterol and lessen heart attack risk. Snack on them between meals, or 30 minutes before your next one.Fresh fruit and veggies certainly don’t have the fill-you-up fat, but they’re loaded with fiber and will stave off hunger longer than simple carbs without fiber (like soda, and even fruit juice!).When altering your eating habits, start with consistency. Choose the same foods, and keep one meal that you change up. Eating healthier doesn’t mean depriving yourself when you’re hungry. Small portions throughout the day will keep you from going into starvation mode (which triggers that I-need-to-eat-everything-now urge, and makes your body store fat). Remember what we say in “You: On A Diet”—you do not have to travel through the valley of pain and suffering to unleash your thinner waist—just Diet Smart, Not Hard.

READ MORE: The Scoop on Snacking