If you're already fat, you're pretty much fucked.
That's not true, and that's a mentality that justifies self-destructive behavior. I used to be overweight but turned it around a few years ago, and in my case it boiled down to fixing some incredibly unhealthy habits
1) better sleeping habits. I used to go to sleep at 3-4 AM, now I force myself off of electronics by midnight and read a book or write until I doze off. Nowadays, when I first get up in the morning, I roll out of bed and do some pushups to avoid the crawl back to bed.
2) better eating habits. Eating breakfast is probably the best thing you can do for your diet. I found that I was eating much more later in the night, so as I shifted my sleeping pattern I also shifted my eating pattern (eating much more at breakfast and lunch and much less at dinner).
3) better exercise. It started with simple things: going to the grocery store, rather than waiting for the closest parking spot, I would park at the far end of the lot and walk the extra N steps; after a few months, I purchased a collapsable cart and just walked the mile from my house to the store. And bit by bit I would try to increase activity.
Obviously everyone's experience is different, but please don't propagate the idea that overweight people can't lose weight