This is based on so many things other than size.
I was clinically anorexic at 97lb with a BMI of 15 when young due to medications I was on that destroyed my appetite but could maybe squeeze into a 10 back then (really a small 12 at a push) because I'm pear shaped have wide hips and broad shoulders (my waist however was a small 6).
I'm now healthy weight at 10st and size 14 in jeans and 10 round waist. I have never been called fat, I used to always get called 'skinny' (all the time) and now if weight comes up people say I'm normal/slim.
My best friend was average weight/BMI but is the opposit apple/lolly shaped with huge boobs and all her body weight in her belly. She is super tall and has long skinny legs, small bum and slim arms. She was bullied for being 'fat' at a size 12-14 (round the waist) because her belly looks big on her slim legs but she easily fit in skinny size 8 jeans that I had no chance of ever getting in.
I eat 1 evening meal per day (like burrito or pizza or pasta etc...) and sometime a lunchtime snack (like a sandwich or pot noodle or bag of crisps etc...), personally never seen the point in breakfast.
food timetables are very unnatural, fasting has benefits and eating for the sake of it when not hungry (outside of medical issues) is never good for you.
Shape or not though (unless very active/athletic or very high metabolism like some teens with growth spurts) I honestly don't know how some people eat 3-4 full meals per day plus snacks (or even afford too eat that much). Many I speak to think thats average/normal and 'healthy' amount (breakfast, dinner, tea, supper etc...) and tell others they are 'starving themselves' or fasting is 'unhealthy' (lots of throwing around of the phrase 'starvation mode' which is just bollocks). However they also tend to be the ones to complain about their weight the most, almost like a correlation exists.
OP you may never be a size 10, not everyone can be but being bigger than a 10 doesn't = fat. You can be 'skinny' but still be over a size 10 and unhealthy, you could also eat loads and big/heavy and be very fit & healthy (look at many pro weight lifters or athletes).