I find this workout video really hard but is it actually any good?

It's this one:

http://www.youtube.com/watch?v=FTT4W8ygJ7w

I was wondering what other people thought. I found it hard to finish but I'm so unhealthy at the moment. I was put on Zoloft/Sertraline and put on about a stone in a month, and can't seem to lose it, so trying to increase my activity levels and eat healthier more.

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