Are You Working Off That Snack?

Have you ever found yourself munching on a granola bar or peeling a banana for lunch? To the average American, these items are considered harmless, even healthy, additions to a person's diet.

But not so fast, says Charles Platkin, a self-proclaimed "diet detective" and syndicated food columnist who specializes in public health. "The whole idea is to understand the value of a calorie," he said. "People don't understand the value of it. They may know what it means. They may have heard it. But they don't have it as a reference point."

Watch the story tonight on "Nightline" at 11:35 p.m.

1 Banana = 13 Minutes on the Treadmill

Platkin believes that with each excess calorie, there must be a trade-off -- more exercise or more weight gain. His approach to dieting pairs the caloric intake of foods with their exercise equivalents. In his book, "The Diet Detective's Countdown," Platkin merges a list of 7,500 foods with corresponding exercises for walking, running, biking and even yoga.

A raw banana? "It's 121 calories," said Platkin. "It takes 31 minutes to walk off, 13 minutes to run it off, 17 minutes to bike it off." Granola? "[A serving] is roughly about 300 calories. That's 38 minutes of lap swimming."

Platkin says the average person has roughly a 2,000 calorie budget. These are the calories burned daily simply by doing everyday tasks. But if this "caloric budget" is surpassed, we either need to exercise more to burn it off, or risk gaining weight.

Platkin maintains that his plan goes beyond calorie counting. "I lost 50 pounds 14 years ago," he said, "and I kept it off for those 14 years, and I never counted calories. What I did was, I learned what was splurge-worthy and what wasn't, what I could afford within my daily caloric budget. When I went calorie shopping, I became a wise consumer and that's what we want people to do."

Too Simple?

Not every diet expert is impressed with Platkin's plan. Dr. Arthur Agatson, creator of the wildly popular "South Beach Diet," thinks Platkin's approach is too simplistic. He says a healthy diet consists of "the good fats, the good carbohydrates, lean protein and plenty of fiber.

"It's not so much how many carbs and how much fat," he continues, "but the quality of the carbs, the fat, the fiber. You can try and cut calories, but if you're eating starch you're going to be hungry all the time. You're going to be in trouble."

Sheah Rareback, a nutrition professor at the University of Miami Medical School, also sees limitations in Platkin's plan. She believes portion size is the real problem for overeaters. "Some people would pick up a bag of chips and think, 'oh, a portion,'" said Rareback, holding what many would view as a single serving bag of potato chips. "But if we read the label, we're going to see that one serving of chips is eight of these big chips. I don't think anyone is going to eat eight chips."

Thinking About Food Differently

Platkin also acknowledges that portion confusion plays a role in weight gain, but says his approach takes that into consideration. "You know, portions are a bit of a game," he said. "We tend to over-consume and we tend to underestimate how much we consume and we tend to overestimate how much activity we actually get. So, you know, kind of a double whammy."

But with some foods, Rareback believes Platkin's idea of exercise equivalents can be beneficial. "If I was going to pick up a big chocolate chip cookie," she said, "and the label told me if you eat this, you're gonna need 20 minutes extra of walking, it would just make me think about it."

This type of thinking is why Platkin believes his plan can resonate with people. "It has to entertain and engage them," he said. "And when you know that it takes 26 minutes of dancing to burn off a handful of chips, you think about it. It's something that you talk about over the water cooler. It's something you become passionate about."

ABC News' Talesha Reynolds and Jeffrey Kofman contributed to this report.