Before you spend too much money on so calle d test boosters...rule out low testosterone first by getting bloodwork done. If it is low maybe you can figure out why it is lower than a normal man your age (ie stress, overtraining, etc). Or just have your doctor prescribe the meds you need like androgel or GH.
I think supplements are good for somethings but if they were effect at naturally raising test in a cost effect way, no one would use illegal steroids.
Look at other symptoms too. Is your libido low, do you feel like you lack some healthy aggression, do you feel "blah" most of time. If so it sounds you natural test may be low if not it can be many things. Either way at 48 a little extra hormone boost from doctor prescribed pharmacology would probably do you good.
Good luck losing weight and getting your energy back!