Why exercise is not a good response to a bad meal...

Point #1:  We can consume energy at a much faster pace than we can expend.
Point #2:  Stored body fat is energy we haven't used yet.

Ask yourself how fast you could eat a cheeseburger, fry and pop (about 1000-1500 calories)? With a bit of focus probably less than 5 minutes.  Do the math and that's about 200-300 calories per minute.  Now lets look at some popular activities we use for exercise...  At best you could run at a nearly impossible pace (over 10mph) and only produce 20 calories minute expenditure.  So considering the worst case scenario for eating and your best case solution for exercise and you have a huge discrepancy (nearly 280 calories per minute which is nearly 1lb of fat every 12.5 minutes)!

Okay... so the math is a little fuzzy and there are a lot of other points to consider, but I think this is another example of why diet and exercise behaviors need to work together as a part of a healhty lifestyle rather than being two behaviors that battle each other.