You have to JUST FUCKING DO IT man. There are ways to make it easier, but ultimately motivation comes from within.
I was like you for many years... I had an enormous Steam library of games I didn't even enjoy, and I'd just sit at my computer all day drinking soda and becoming obese. Then I started to hate how pathetic I was. I was a fat slob who was still coasting through college getting A's, but basically wasting my life and not living up to my potential... and of course I didn't get much attention from the ladies either. And I was depressed as shit. I felt very bad about myself, and I started to hate myself for letting my body get so bad.
Comparing yourself to others can be useful sometimes. I realized that while I was sitting in front of the computer getting fat and wasting my life on a liberal arts degree, there were other guys (real men) getting ripped in the gym, running marathons, making money and fucking bitches. This saddened and infuriated me.
So I channeled that self-hate into change. I started working out, lifting and then doing /r/bodyweightfitness (amazing subreddit, highly recommended), and recently I've started running and that's even more fun. Exercise is essential. It will make you a better, happier person. And I've lost 40 pounds in the past year or so. I'm still not getting money and fucking bitches, but I've made a lot of progress.
So really you need that fire within you that drives you to change. Without that, you'll remain the pathetic slug you are. However, there are a few "motivation hacks" that might help you out:
Have reasonable goals. Goals should be specific, measurable, reasonable, and time-related. Don't make your goals so vague that you can cheat, and don't make them so difficult that you're bound to fail. Start small and work your way up.
Start things, because just getting started is always the hardest part (psychologically... it's not actually difficult). If you don't feel like running today, say, "I have to run for at least 15 minutes, then I can decide if I want to quit or not." You'll probably keep going.
Fuck video games. I deleted Steam and quit cold turkey. If you have a lot of friends who play games or still have some games you really enjoy, this might not be advisable, but for me games were just a waste of time so it was easy and beneficial to quit.
A Kindle makes reading easier. I just think it's way more convenient, plus you can pirate any books you want.
Read in chunks. Sit down and say, "I'm not moving until I've read 40 pages." It will go much faster than if you get distracted and stop every 10 pages.
Pomodoro technique for optimal performance - devote 25 minutes to focused work on something, then take a 5 minute break, repeat