I used to struggle gaining weight. Before I was 28, I never weighed more than 119 at 5'7". People would always comment on how tiny I was and saying they wished they could be skinny like me. I'd tell them I have a high metabolism, which isn't untrue, but I really wanted to tell them my secret was having massive bouts of depression where I only eat a handful of crackers or whatever at a time.
I have a bucket list in my phone and one of the items is "weigh more than 120 pounds." I thought that once I achieved it, it meant I had finally beaten depression. The day I went to my annual physical and weighed in at 125 was one of the happiest days of my life. (Still depressed af though lol.)