Hey there. im 17 years old (male) and im underweight. My BMI is 18.5 but should be at least 20.
I have skinny arms, average legs (i think), but my upper legs, butt, and my stomach + sides are flabby and quite large.
What i want, is to gain weight, but burn off all that extra fat, aswell as generally beef myself up. I would also love to start developing a six-pack and a tight butt.
Can anybody please give me some advice and/or refer me to to somewhere online that can help.
Thanks

do a light amount of cardio maybe around 30minutes 3 times a week. then do tonin for your entire body everyother day three times a week. it works for me.

lift weights. Building Lean muscle mass with add the weight you want, and muscle burns fat, Also do cardio 2-3 days a week, and eat only healthy foods that consist of protien, complex carbs, and oils. dont expect immediate results. start a little journal. even take a picture of yourself each month or so to compare. You will see bigger gains looking from month to month than day to day or week to week. Good luck