I'm a pretty fucking underweight person (over 6 foot tall and 150 on the dot). I don't exercise much besides doing pull-ups on my door frame pull-up bar everytime I go into my kitchen, so I'm confused how I could actually lose weight while basically sitting in a chair all day

But I've heard weight gain shakes can potentially mess up your kidneys (happened to a friend of mine) and they aren't well-regulated (just kinda jampacked with all different good and bad nutrients)

Anyone know how a poor person cam gain weight?