DO I NEED TO USE 2-TAILED OR 2-TAILED RESULTS? WHY?

Question

A researcher believed that 2 hours per week of intensive exercise would result in significant weight loss after 12 weeks on the schedule. Accordingly, he weighed a group of 50 subjects before and after the 12 week exercise period.

Answer 1

I would use a one tailed result. http://en.wikipedia.org/wiki/One-_and_two-tailed_tests

Answer 2

Rawr