[Captain.Remy]

The TIBB Gods know I don't always agree with Marsh, but come on guys, he's not wrong about this. He didn't say gyms don't help to keep weight off, but that gyms are not the only way to keep weight off. The post was crystal clear. So on this note indeed gyms aren't always necessary to keep weight off.
And it's actually true. Some people keep weight off through different ways: swimming, eating better (which you need to for the gym exercices to work properly anyway), walk, play a different sport, reduce stress etc In the end the common factor is to eat better and move more. Plain and simple.

I was a fat kid and then played rugby first for many years before hitting the gym from the age of 15. At 15, I was big but not fat and hitting the gym kept me at a good weight level. I could have done without it, had my end goal was different. Some of my rugby mates never hit the gym and kept weight off too.
So it really depends on your end goal. Different means for different people, and not all techniques work for everybody. You have to find your own.
At the end of the day, promoting healthier eating habits and encouraging to move more (and better!) is the way forward to prevent such rising health crisis.