Depends on your weight. If you are motivated and can actually pass the IFT then you'll be rotated through a regular platoon in boot camp. If that's not the case then you'll be put in PCP until you either lose the weight or be able to pass the IFT.
If you can't do either before you go then some recruiters will work with you to help you lose that weight and get you in shape before you go. It just depends on how motivate you are.
EDIT: AD when I went through boot camp I saw a few really overweight guys go through. To be honest they'll take you and then get you to lose the weight.
if you're a little fat, then yes.. they will not take a 300 pound, 5"11' guy or gal
No you cannot join if you are "fat" but they will except you if you are a little overweight.
Ship Weight 230lb
Max Weight 208lb
No, they aren't going to waste their time getting somebody who is overweight in shape when they would rather take somebody who is already somewhat in shape. There are height and weight standards to enlist. I know Full Metal Jacket had Private Pile on there but that movie was based during the Vietnam War and they had lower enlistment standards back then along with a draft. Today, the military is all volunteer.
@ Rob: How long ago did you go through Boot Camp? According to the Marine recruiter next door to us either you make HT/WT or you don't get in. They gave us a referral we put in the Army because he couldn't make weight for them and they wasn't taping anybody at the time. Enlistment standards change all of the time based on recruitment goals.