What Changed/Happened?

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Last year (in 2011) I was able to loose eight pounds in one month by doing cardio alone. I was doing cardio 60 minutes a day, 5 days a week. This year I only lost two pounds after dedicating a month to the same kind of cardio.

Keep in mind I stopped exercising for 4 months prior to starting over again. What may be the reason for this? Why am I not losing the same kind of weight within a one-month process like I used to?

I also implemented the same kind of diet as I usually do when exercising & trying to lose weight.