From my personal experience I gained around 80 lbs while working a cubicle job over some 12 years.

In 2007 we gave up eating ANYTHING where the majority ingredient is sugar.

In 2008 I was laid off and started doing some computer repair type work to bring in a few dollars here and there and subsequently got back into a trade type of work (HML or Hard Manual Labor).

I signed up with a personal trainer about 6 months ago who has us lifting weights and doing some 45 minutes of fairly vigorous aerobics.

He has us eating small meals every three hour or so and every three months doing 3 days on no carbs for a month which is the part I have found hardest.

For all this effort I am down a bit more than a pant size and have lost some 35 lbs. The important thing I think is that what I am doing is sustainable.