Sorry, but I think a lot of people here are telling you what you want to hear. For nice reasons but reality doesn’t back up what they’re telling you and deep down you know that hence starting this thread.
The reality is that yes you will be judged negatively by many even if it’s just a fleeting first impression (if you are as big as you say) before they move on to the second impression. Society is told everyday that fat is bad, slim is good. The interviewer has not been shielded from these messages.
Things are improving but people are discriminated in interviews everyday for their appearance be it based on race, ethnicity, accent, dress sense, visible tattoos, size etc.
However, most interviewers even if they do harbour some level of unconscious bias against obese people, will easily be able to overcome it if you make a big effort with your overall appearance. You must be very well groomed, light make up, short nails, well cut smart clothes, good hair cut/colour. Essentially if you look well maintened and healthy, any fear they have you may be unhealthy, off sick loads,not be able to keep up with physical stuff etc will be put to rest if you look healthy, smiley, confident, well groomed and say the right things.
Good luck.
As an aside, the fact you’re so worried about your weight indicates you really need to make efforts to lose it (in a gradual, healthy way).