The school year's started, and everyone's headed in different directions. We'll grab fried chicken after football practice, a burrito before tennis, hot dogs during the game, a burger and fries -- maybe pizza -- on the way home. Could we make it through the week without fast food?

Walk into your favorite fast-food joint, and "that smell of salt and fat in the air is almost irresistible," says Joan Carter, RD, a nutrition instructor at Baylor College of Medicine in Houston.

"I love french fries," says Cynthia Sass, RD, a senior dietitian at the University of South Florida. "You can't ask someone to give them up for life. It's just not realistic."

Let's face it, fast food is part of our busy lives -- even for those who make nutrition their career. It's a challenge trying to avoid the convenience. Should we be trying harder?

Facing the Challenge

In fact, no fast-food splurge blows your diet. "What counts is what you eat in a day or over a few days," says Sass, a spokeswoman for the American Dietetic Association (ADA).

"Nutrition is not all or nothing; it's about balance," she adds.

The typical fast food meal: sandwich, fries, and soda. But you can balance it by:

• choosing small fries and water -- nixing the supersized meal. Also, nuggets or grilled chicken are a good substitute for a burger. And toss the bun -- you don't need it.
• detouring to the grocery store after the fast-food stop. Prewashed fruit and veggies are a high-convenience item there: baby carrots, a small banana, an apple. Cherry or grape tomatoes are plentiful during summer. Just wash and eat them as a snack.
• carrying dried fruit with you, like dried figs, dates, lemon- and cherry-flavored plums, peaches, pears, cherries, or blueberries.

Also, ethnic take-out foods -- like Chinese, Thai, Indian -- tend to be very rich in vegetables and lighter, so they give you lots of nutrients and more energy than barbecue or burgers.

"It's all about compromising, about deciding where you can give up something or what you're willing to add to give balance," Sass tells WebMD. "That's the kind of philosophy people can manage long term. Otherwise, it's just not realistic. Every time of year is busy. Not all of us can pack a healthy lunch."

"Eating right doesn't mean you have to become a perfect eater," she says.

Best & Worst Fast-Food Picks

To help guide you at the fast-food counter, the nutrition gurus at the Center for Science in the Public Interest (CSPI) recently issued their choices.

Burger King was panned, with its Double Whopper with Cheese, french fries, Old Fashioned Ice Cream Shake, hash browns, and Value Meals cited as "the worst."

"The best" fast foods:

• Wendy's Mandarin Chicken Salad -- mixed greens, chicken breast, roasted almonds, mandarin orange segments, and half a packet of Oriental sesame dressing make this 420-calorie salad taste as though it were served in a downtown bistro.
• Burger King Chicken Whopper Jr. -- any grilled chicken sandwich is a good choice, but this one actually tastes grilled. The junior size is best -- just because it's a normal-sized sandwich. The junior has 350 calories, while the regular Chicken Whopper has 580 calories.
• Subway's Low-fat Subs -- the new low-fat select subs -- honey mustard ham, sweet onion chicken teriyaki, and red wine vinaigrette club -- range from 310 to 370 calories are "downright delicious."
• McDonald's Fruit & Yogurt Parfait -- eat it for breakfast, as a snack, a dessert, or a refreshing lunch, suggests CPSI. It's two-thirds cup of luscious berries layered between low-fat yogurt and topped with crunchy granola -- all at 380 calories and 2 grams saturated fat. Skip the granola and it dips to 280 calories.
• Burger King BK Veggie Burger -- it's the first meatless sandwich from a burger chain, with less than two grams saturated fat and fewer calories (330) than just about any hamburger at any chain.

Exercise Makes the Difference

But if those biggie fries are calling your name, go ahead and enjoy them once in awhile, says Carter, also an ADA spokeswoman. "Life's too short. Anyway, no one wakes up one morning weighing 600 or even 300 pounds. Just like one day in gym will not make you Arnold Schwarzenegger. It isn't one food, one day, that will make you fat."

Just remember, it all adds up.

"You can very easily put on a pound a week, or a pound a month by going overboard, by simply eating an extra 100 calories a day," she tells WebMD. "Calories go down a lot more easily than they are burnt off. When people realize how slowly you burn calories, it makes a difference. The difference it makes is cumulative over time."

"The key is to burn up those calories, and that's not as easy as most people think it is," Carter says. "You might burn 180 calories if you walk an hour -- but you haven't even burnt off half the calories of those biggie fries."

What you'll burn in hour, if you weigh 110 lbs.:

• Driving burns 115 calories
• Mowing the lawn burns 225 calories
• Yoga burns 200 calories
• Skating burns 275 calories
• Laundry burns 100 calories
• Food shopping with cart burns 100 calories

In one study, people who lost weight -- and kept it off for five years -- were those who burned about 400 calories a day in exercise. They walked four miles a day. "They had to do it religiously, because not all of us have this wonderful metabolism. For most people, four miles is going to take about an hour."

Exercise has a way of tempering your cravings. "The more physically active you become, and more aware of how hard it is to burn off those calories, the easier it is to say, 'small fries is fine,'" says Carter.