What advice would you give a 29 year old who is trying to finish school, lose weight, and re-join the military as an officer?

As for the weight you have two options. Maintain a steady diet and do a fitness program, maybe one from Bodybuilding.com (Do a cutting program since that's your main goal) or go oldschool Marine Corps and Run and do Calisthenics. The aerobic activity will help you cut calories regardless.

Now for some advice in becoming an officer, don't forget your roots. You started out enlisted, remember all those things that seemed a little off? Now you have an opportunity to change them, but don't go over the top. Remember another thing is you're going into a different branch. I recommend saying that you were a Marine as little as possible unless it comes up. I know some Army -> Marines and they said that the Marines that came into the Army were the most narcissistic bunch. it's fine to say you were enlisted and served in their shoes before and you can bring up the Marine Corps. Just don't be obnoxious about it, I.E The Marine LCpl's I served with were 10 times better than you etc. Also good luck and congratulations once you get in brother!

Ok, I have been there and done that. First forget fast and just be consistent in your exercise routine. Depending on how out of shape you are start walking everyday come rain or shine. Increase the length and the speed. ( i was way out of shape so i walked for a full month.) Jogging came next then running so i could meet the PT standard. I filled in with the pt before or after i'd been running. ie push up, sit up, overhead bars or what ever passes for qualification exercises these day. Start slow and add one or two reps to your initial starting maximum every other day. I know that there are other ways of getting in shape but to get into basic shape this will get your mind and body into the routine of exercise and from there have at it with a program that can challenge your goals. One caution though, avoid going all out and getting injured as an injury can not only set you back but could hurt your career goals; nothing counts if you don't finish on your feet. I saw many soldiers destroyed trying to break records on obstacle courses and road marches. Good luck and after Marine Boot Camp i have no doubt you have the discipline. Eat right and forget smoking.

It would be an inspiration and motivation to the troops you serve; not to mention the experience you would bring. I would be more than proud to serve under the leadership of such an officer.