Here's another popular one. We all know someone (or maybe you are that someone) who tries to stay in shape, so they hit the gym a few times a week. The only problem is that right after you leave the gym, your next stop is the drive-thru at the fast food joint or the couch with an enormous bowl of calorie-packed ice cream sitting in your lap. Don't laugh! This situation is more common than you'd think. Many people are under the assumption that since they work out multiple times a week, they are "allowed" to eat whatever they want because they are going to burn it off at the gym anyway. Sorry, but unfortunately it doesn't work that way.
EXERCISE CANNOT MAKE UP FOR A POOR DIET!
While a steady amount of physical activity may be able to mask some of the effects of a poor diet, it won't completely cancel out the excessive fat and calories. Most people don't realize how easy it is to consume 1,000 calories, and how difficult it is to burn that same number of calories off.
A thousand calories sounds like a lot... and it is. Consuming this amount of energy from nothing but fruits, vegetables, whole grains, and other healthy snacks would take a large amount of food, but with the temptation of fast food restaurants, high-calorie packaged goods, and overwhelming portion sizes, taking in 1,000 calories in a single meal is much easier than you think. For instance, a Big Mac® and medium fries, a common American meal, stacks up 1,040 calories, and that doesn't even include a beverage.

The truth is that many people aren't aware of the amount of calories that they are ingesting. If we're going to beat (or even effectively combat) the obesity epidemic that has taken a firm hold of our nation, we need to become better educated about the calorie content of our favorite foods. See "Belt-Bustin' Foods" for a list of foods that can lend to a mind-boggling calorie count.
America's approach towards diet and exercise is complicated enough by ignorance towards the monstrous calorie content of some of our favorite foods, but couple that together with a lack of knowledge in regard to calorie expenditure and it is no surprise that such a large percentage of our population is struggling with weight issues.   While  most people  realize   that burning 1,000 calories isn't like snapping your fingers, they still underestimate the amount of physical activity it takes.
Let's take some common activities as examples. Riding a stationary bike is a popular cardiovascular exercise, and at a moderate pace it would take nearly two  hours  for a 175-pound person  to burn  1,000 calories. A tad bit more than the standard thirty minutes you usually spend riding the bike at your local gym, right? What about running? At a 10-minute-mile pace, a 200-pound individual would need to maintain that rate for an hour to cancel out 1,000 calories - a difficult task for someone who is not in the best of shape.
As you can see, burning 1,000 calories isn't exactly a walk in the park, literally. It takes a considerable amount of effort. And, if you consume 1,000 calories over what your body needs to maintain a healthy weight (which isn't that tough as demonstrated earlier), you will need to put forth that much more effort to rid yourself of that extra baggage.