I am 18, male, and weigh around 155. I have been working out for a couple months now. At first I would just workout 3 times a week at home doing pushups, pullups, and situps. I did that for about a month and decided to start going to a gym. For about a month now, I have been working every upper body muscle 3 days a week with no cardio and usually just a protien shake after every workout. I have seen some results but i think they could be better. So i have decided to do a 3 day a week split working each muscle group once a week. Chest/Tricep on Monday, Legs on Wednesday, Back/biceps on Friday.And i plan on doing a 15 minute HIIT session 2-3 times per week on the off days. I will also try to eat a lot more protien through shakes and meat. Is working a muscle group just once a week enough? I think it will give my muscles more time to rest and recuperate. Also, will the HIIT sessions deter any progress in my weightlifting? I would like to gain a little more muscle but lose some fat. I am actually pretty skinny but i have some love handles and some fat on my abs. thx for replies

Yea, just do a pyramid of the weights, starting light and doing something like 10 rep - 8 rep - 6 rep. The last rep on the last set of any exercise you do should be to failure. Eat a lot of protein as well!

Forgot- add shoulders in with Legs on Wednesday.

Actually the HIIT will help you build even faster by delivering oxygen and prtein rich blood deep into the muscle for a quicker recovery, it's a common myth that cardio hinders progress, but it's quite the opposite