Yes you can -- but I wouldn't do it all at once. If you go from nothing to full-speed, you risk being sore (maybe even hurting yourself), getting discouraged, and dropping out. The best results are obtained through time and CONSISTENCY, starting and staying with a program over the long term is what you want, IMO.
I love the Biggest Loser, but their exercise regime is unrealistic for most people. They are medically supervised and professional coached. Yes they work REALLY hard, but they have a support team watching out for them too. We don't have that luxury.
Getting back to the gym is great, but I would just caution you against hitting things TOO hard, too fast (and only you know what that is, based on your current fitness level). One way is to alternate hard and easy days, or on your "off gym" days, take a nice walk or do some other kind of moderate cross training activity. You want to be able to ramp up the intensity over time, in a sustainable way.
Just my thoughts!!