I see a lot of posts about how if you try to intentionally lose weight you'll almost always gain it back. but is that talking about people who are naturally a heavier weight? I've used food as a comfort and boredom stopper for many years and haven't been active enough because my depression wouldn't allow it and am almost 300 lbs because of that. if i am able to become more active and develop a healthier relationship with food will it stay off, or will I still gain it back?

I am going to gently confront a few assumptions in your message.

I’ve used food as a comfort and boredom stopper for many years…

Thin people do this too, and their eating habits are not pathologized. Maybe these eating habits are normal? Maybe it is not why you are fat? Maybe you are eating because you are hungry but our culture has taught you that any hunger and any eating is bad or for the wrong reasons simply because you are fat?

… and haven’t been active enough because my depression wouldn’t allow it…  

Hey, did you know that exercise doesn’t cause weight loss? Did you know that fat people are often less active than thin people, but when we do move, we burn more energy, so maybe its all a wash anyway? Maybe your activity level is okay? Maybe when you are dealing with a chronic illness like depression its okay to be less active? Maybe it’s ok to rest when you are sick? 

… and am almost 300 lbs because of that

Your weight is not determined by your behaviors. Genetics and social determinants of health like poverty, food insecurity, dieting (!), and childhood adversity explain nearly all of the individual differences in weight that are observed at the population level. What if you weight doesn’t need to be explained? 

What if your weight isn’t something you need to feel guilty about?