Apparently research has discovered that BMI at the onset of puberty will dominate your set point as an adult. So if you were the skinny kid at puberty you are that who can eat constantly and not blowup like the Michelin Man. So think back and see what you are up against.
Gaining weight is a gradual process adding up pound by pound until you reach that moment the guy in the mirror freaks you the fuck out. You stop trying to date civies and get on NightShift. Don't fear there is salvation.
I spent several years at the University of FCI Lompoc. I arrived there at 6' 230 pounds of cherubic bliss, (too much Top Ramen as an undergrad at MCC Chicago). To my surprise Lompoc was teaming with every kind of medical specialist imagineable. Those doctors (medicare fraud) had their own private forum so-to-speak and it focused on weight loss for incoming "students".
As pointed out by others the key to weight loss seems to be "work"; moving weight in a measured rate of time.
What this boils down to is your out of shape body has adapted to moving your hulk slowly around the planet with your existing muscle set. The first step is to start a walking program i.e. 10k steps. At the U it was 10 days. On day 11 you add weight so your existing muscle set needs to work harder to keep the pace established in the prior 10 day period. On day 30 you add more weight. Do not add weight so as to cause a break down. If 2 aspirin are good, 30 aren't better.
On day 40 you shed the packed weight and jog to the same distance while cutting the time to reach the distance. 10 days at jogging only. Day 21 you add pushups, squats and lunges. Start with 5 each after each 5 mins of jogging. Each day add 1 rep to the trio.
Month 3 you add dead lifts and start bar work. 1 chin up, 1 dip, 1 pull up. Add reps as able but do not be stupid and injure your self.
After 6 months I was able to run 7 min miles, do 25 chins with a 25lb wheel strapped to my belt and my weight was 185.
My diet was self controlled and even on weekly binge night I rewarded myself with a pint of Ben-n-Jerrys Heath Bar Crunch, 1600 calories in a single serving.
I did this process at age 51. I was a chubby kid at puberty. Not considered trim by any means today but able to stay at 205 at age 65.
Good luck. The work becomes a habit, you will look forward to the laps and especially the bar work. Very rewarding to see how fast 1 dip becomes 5 and then knocking off 50 at a time. Trust me, as one lazy mfer, the work becomes play.