It’s 3:15 p.m. You’re in your car. Dinner is three hours away and your stomach is growling. There’s a fast-food restaurant up ahead. You pull up to the drive-thru and try to pick something that won’t torpedo your diet. But it’s easy to screw up. Even a seemingly innocuous choice like five pieces of chickenbreast strips at McDonald’s comes loaded with 630 calories. A milk shake can easily top 1,000 calories. Sweet drinks at Starbucks can also pack on the pounds.

Although there’s no magical number for how many calories should be in a snack, try to shoot for under 250, says Lisa Young, Ph.D., R.D., and adjunct professor at New York University. And watch out for fat. For a 2,000-calorie diet, you should shoot for no more than 65 grams of fat per day. But many fried snacks--even some of the ones listed here that are low in calories--can quickly gobble up much of your daily allotment, so eat them only every once in a while. Use the chart at right as a guide.