It's absolutely possible. But you need to increase and improve your diet beyond what you consume for a sedentary lifestyle. Garbage in = garbage out, so eat nutritious food (and yes, organic really is better). Live on McD's and junk food and it won't matter how much of it you eat or exercise, you will not be healthy. If you're increasing your workload it also stands to reason that you need to increase your fuel intake; protein to build muscle, carbs to give them the energy to function, fat in moderation (unsaturated are good, but a bit of saturated is not bad either - just avoid the trans fatty acids that come from processing food), vitamins to help the body metabolize protein and perform other crucial functions, etc. You don't need to go crazy if you're just trying to burn off some weight and increase cardio, that type of thing, but if you are trying to build muscle mass you need to increase fuel input enough to allow that to occur.
Supplements generally let you work out harder, stressing the muscles more and triggering a more aggressive rebuild process. Some will actually make your blood chemistry change causing muscles to grow faster, those I am not sure about the long term risks of personally. But supplements mean zilch if the underlying diet is crap. Always, always start there.