I decided to get back in shape and have been exercising for about a week and a half now. I lift a pair of 3lbs dumbbell in between three 20-minute cardio activity. Someone said I should switch to heavier weights after 2-3 weeks. Is it advisable. I'm not trying to bodybuild, but just trying to reduce my weight.

Does it work different muscles more when you have your palms facing forward vs facing each other when doing flat dumbbell chest press or dumbbell shoulder press? Or is it pretty much work all the muscles the same just easier on the wrists for some people?