Marine Active and Reserve both go through the 13 month hazing process called hell. I lost 25 pounds of bootcamp that I didn't need to lose. Some lost more. One kid, he got put on light duty the whole way through, got fatter through out. He's a shitbird. They fixed his ass.
Work on the pull ups, crunches, and run time. To get a 300 pft you'll need to do 20 pull ups, 100 crunches in 2 min, and run 3 miles in 18 min. you'll Pt 3 times a week, and make many trips to the Pit
Don't plan on gaining or maintaining weight. You'll be put on a diet that won't have much fat, and many nights you will go to bed feeling hungry. You'll learn to eat whole meals in less than 5 minutes b/c you don't know if the drill instructor will say "Get Out". Thats it chow time is over.
If you're going to go Marine go for it. Once you do bootcamp you will never have to go through another basic training again. Everyone who wants to be a Marine must go through bootcamp, or OCS for those punk ass mother fuckers who become officers without spending any time in the enlisted man's boots. The level of respect they receive from enlisted is strictly due to the fact that we are disciplined enough to respect the rank structure which means a Marine can be in 20 years as enlisted, and has to call some 2nd Lt who just got out of OCS "sir". Joke told in the Corps is what's the difference between a PFC and a 2nd LT...The PFC has been promoted once.
PM me if you want any more info on USMC bootcamp.