"I never had to lie to anyone about joining the military. The secret is that no one walks into my office if everything is going right in their life. I just find what that problem is, and figure out how the military can solve it."
Recruiters can't effectively tell you lies if you know everything you need to know. In my case, my father had been a sonar tech and had told me what to expect like what I posted up there -- I already knew what I was getting into when I walked into that office. Don't go to a recruiter (and potentially waste their time) if you haven't done the due diligence to research a very life-changing decision.
"When they ask you if you want to be a Nuc, say no." -- he could have got a lot of good will at his recruiting office if I chose to be a nuclear tech, but he was absolutely right in telling me this. They never came to ask me, because I had never taken algebra in high school.
"If you have a choice between an east coast and west coast ship, choose west coast." -- Absolutely agree with this. West coast is a much more relaxed attitude compared to east coast, unless you're forward deployed.
"In bootcamp, get the yeoman job." -- I listened to him and was able to get the division yeoman job. This allowed me to travel around base by myself -- something you'd appreciate if you've been through the bootcamp experience. It also led to me getting a meritorious promotion (only 2 or so recruits per division of like 30-50 got this), and getting promoted earlier decreases the amount of time required for you to advance to the next rank.
"Run a lot before you go to bootcamp". Ironically, he was a very slow runner, but I took his advice and worked out nearly daily for the two months before I left. At the time, in order to pass the run test and graduate from bootcamp you were required to run 1.5 miles in 12:15, which would have been nigh impossible for me had I not practiced a bunch beforehand. I eventually got it down to 10:25 in bootcamp, which is a decently admirable run time. Women get approx. an extra minute longer.
I really hope those three guys were in the minority, but it left a bad taste in my mouth.
That being said, certain common diagnoses will preclude you from entering service: ADD/ADHD, bi-polar disorder, bad knees, fibromyalgia, among other things. Obesity is kind of a no-brainer thing -- there's a maximum body fat percentage and height/weight ratio.
If it's in your health record right now, then it should definitely be declared, in my opinion. You'd only be doing yourself a disservice later on by not doing so.