Here's how I understand it.
Lifting heavy is for building strength. If you don't want strength, maybe don't do it. If you are fat or have a body that gains fat easily, you have the type of body that can also build muscle and strength. Getting strong has its own benefits and lots of them. So do a strength building program if you want to be strong.
If you just want to be skinny, then lose weight and don't focus on strength. There are a million ways to lose weight, some of which work.
In my own experience, I am not skinny but I am okay weight-wise. Lifting heavy hasn't made me lose any weight, but it has changed the shape of my body. I honestly think I look more pleasing. But I'm not smaller and parts of me might actually be bigger. I haven't weighed myself since before October so I don't know how much heavier I might be.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Heaviest squat: 180 x 2. Heaviest Deadlift: 230 x 2