Every bodybuilder on /fit/ and ones I know in real life don't use dumbbells and say they are for ***s.
10 Pushups is worth 50 dumbbell reps, I'm just sayin'...
Edit; wow just read people telling you to do situps. You do situps and I honestly hope you kill yourself, don't put yourself through that shit. 300 Situps is basically a 10 second Plank (the one where you lift your legs up a bit and hold them with your torso)
Protein shakes are only good for building fat, not for maintaining health whatsoever - well maybe a little bit if you lack protein. Just stick to cardio and water if you don't have time, srs.