Does DEP(Delayed Entry Program) actually help get people into shape before they ship off?

If you actually do it. Not sure about USMC, but with Navy, we met once a month on Saturday, but what really helped me is that I got a free membership to the YMCA and was able to go work out every morning. My bro just left for Army boot camp and he did it with them for a few months and it really helped him, but they met once a week and did physical training for about an hour or so. So you do have to apply yourself and it differs from branch to branch, but with the commitment that USMC has, I'd say it would definitely help you out and the training would be pretty good.