In 1 week I lost 13 lbs

[jabarto]

No, Idaho is correct. Our bodies are rather efficient. One-hundred calories is a mile of running, roughly speaking. After that mile, plus a bit more passive exercise, you will be hungry and thirsty. You will not only fail to lose weight, but actually gain some. Read the new studies. Even the Times published an article on this sometime last year. The only way to lose weight is to eat a regular, filling, but yet healthy diet. Exercise builds up health, but it does not cause normal people to lose too much weight, if at all. Only the extremes do.

You only need a two hundred daily calorie deficit to lose weight at a reasonable rate. You are right in the sense that starving yourself is bad, but it's pretty ridiculous to claim that exercise doesn't help. If you lift weights, you will build muscle. Muscles require more calories to sustain themselves, ergo you will burn more of them and lose weight.

Seriously; basic science here.

EDIT: Actually you're sort of right. Exercise doesn't contribute to your weight loss as much as diet but it does affect your body composition which is a factor.