Why do some people gain weight when others don't?

Do you have that friend—the one who can eat endless hot fudge sundaes and never gain weight? Or do you sometimes feel that even if you worked out three hours a day and ate nothing but celery sticks, you couldn't lose weight?

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<p><a href="http://www.physorg.com/news9144.html">Why do some people gain weight when others don't?</a></p> <p>Do you have that friend—the one who can eat endless hot fudge sundaes and never gain weight? Or do you sometimes feel that even if you worked out three hours a day and ate nothing but celery sticks, you couldn't lose weight?</p>