Eat more good food and lift some weights to gain muscle mass. You don’t have to be one of those giant dudes but a bit of definition goes a long way. It’ll also help prevent you from being frail when you’re older. I’d like to continue opening jars and carrying my own groceries for as long as possible. There are a lot of health benefits, and you don’t even need to go to the gym if you get adjustable weights and a multipurpose bench. I’ve been doing exactly this and I’m up 40 lbs and look better. I’m still a tall lanky dude at 6’3”, but I’m not nearly as skinny (165->205lbs).