I got this in the first area of Chapter 3. You have to fight a super soldier, then pull a lever in the back room to open doors on the upper level, then fight your way to the top where a mounted gun can help you clear the area. Once that's done, there are plenty of health packs around to make a run at this trophy (and Health Upgrade I, if you didn't already get it).
The video below shows how I did it. Pick up a few health packs that aren't along this path first, so you start at 100 health. The idea is to boost your health up to 250, but anything above 100 will rapidly decrease, so you have to be fairly fast.
(Edit) It looks like this is much easier in the Prologue, in the big office room, after defeating all the enemies there. Oh well, I'd already put this one together.