Avoid the traps of eating fat being bad. Go easy on the carbs as they are addictive and non-satiating meaning you will easily eat more calories.

Additionally carbs are much cheaper to produce so profits on its are much higher so companies are more inclined to produce food with high amounts of carbs instead of higher amounts of fat.

Stop making up excuses and labels like "plus size" to make it normal. Being obese is simply unhealthy. Look around you and tell me how many obese people of 80+ or 90+ years old you see.