Fast food = slow progress

It's a beautiful day here in the Northeast, more like May than March. I'm going to strap on my sneakers and go walk around town in a minute.

Walking is a great activity for weight maintenance. But its benefit also can be deceiving. It's all too easy to fall into the trap of thinking, "Oh, I just walked for a half hour. Now I can go get that hamburger I've been craving."

Most people overestimate the benefit of exercise and underestimate the damage that fat and sugar-laden food can do. For example, say you eat a Big Mac meal with medium fries. (Let’s assume a diet drink, just to be virtuous.)

According to McDonald’s nutritional information, a Big Mac has 540 calories, while the medium order of fries has 380 calories, so your meal totals 1,480 calories.

How long to you think you’d have to exercise to burn off those calories? An hour? Two hours? Guess again.

According to the most recent government data, a 154-pound person would need to walk briskly for more than three hours to account for this meal! A more sedate pace would require more than five hours of hoofing.

And consider this: Most people who have a plan for losing weight do it by trying to limit their daily calorie intake. That same 154-pound person might have set a limit of 1,500 calories a day. Wow! They'll have a whole 20 calories to play with that day!

And when we're talking fast food, we can't neglect to talk about fat content. Again, consider the medium Big Mac meal. Of the Big Mac's 540 calories, 260 of them come from fat. It contains 29 grams of fat -- fully 45 percent of the recommended daily value. And the fries? Of the 380 calories, 170 come from fat. Their 19 grams of fat are 29 percent of the recommended daily value. So together, the two items account for 74 percent of your daily allotment.

Is that meal really worth it?

Most people who talked with me about their weight loss for How We Did It pinned their weight dilemma on overindulgence in fast food. McDonalds, Wendy's, Taco Bell, Five Guys, Cinnabon, Pizza Hut--the list of fast food outlets is almost literally endless.

So, the next time you want to reward yourself after a workout, banish the thought of junk food. I'm usually starving after I swim my laps and need something with a little protein, so I put together some cheese and crackers and apple slices. What do you do?