u/BazExcel

I just recently found out that I weight 225lbs, meaning that within the past year and a half, I gained probably about 40lbs. Now, I've always been a fat guy (For Reference I'm about 5'9,) and I've always been deeply ashamed about my size. Last time I got REALLY insecure, what I did was essentially stopped eating aside from the dinner my parents gave me, and MAYBE a small snack a day. I also started doing one or two decently long walks a day, on top of the long walks I was already taking almost daily that summer. It seemed to work well enough, but I was only able to do that for a month before school started and it became difficult to maintain. Now it's worse than ever, some of my clothes don't even fit and I feel ashamed whenever I look in the mirror. I can feel everyone judging me silently and I don't blame them at all. It's horrible. Once this summer starts and I've graduated HS, I think I'll do my previous plan again (Difficult because of the discount with my new job at McDonald's, but I can do it.) Now, assuming I walk literally zero steps, and this is only a reflection of my diet, rather than my physical activity, how much weight would I be naturally losing if I cut my diet down to like 500-700 calories daily? I feel like that would be enough to lose a good amount quickly but I'm honestly not sure. I also walk around town a LOT, so I'd be losing those calories too, I think it's a pretty good plan. Can anyone give me advice? For reference, I'm an 18 year old male, 225lbs and 5'9.