Look, your doctor is not going to start an argument with you in his office and call you a liar to your face. I’m not going to call you a liar either, but I do know that a lot of people overlook a lot of calories they consume without realizing it or wanting to admit it to themselves, especially with drinks.
Can I be certain that I’m right in your case? No. Would I bet good money that if I could lock you in a house for a month with no other access to food besides the 1200 cals I delivered every day would you be a lot lighter after a month? Yes. Maybe you’re somehow right and I would lose that bet, but I don’t think I would. Maintaining 262 lbs on 1200 cals a day unless you laid in bed all day stretches the laws of physics in ways that shouldn’t really be possible.
I get your skepticism. The food was prepackaged meals. On most you just added water and microwave it. I was allowed a limited amount of ketchup on the faux burgers. I ate absolutely nothing else.
I only very rarely drink alcohol. I do not drink sodas. I drink a cup of coffee with a little low fat milk and Splenda. Once in a while I drink sugar free iced tea. I drink a lot of water.
My wife and I run our company together, so we are together 24/7. She is normal sized, 5' 2" and about 120 pounds, and eats more than I do, by far. She helped monitor what I ate and accompanied me to my doctors appointments.
Trust me, it is VERY frustrating when you hear "I gave up beer and lost 50 pounds!" or "I stopped drinking Cokes and lost 25 pounds!" There is nothing in my diet like that. Instead, I get to go "I went on a three day fast and lost a pound!" My cardiologist didn't believe me either. He put a monitor on me for two weeks. He apologized after getting the results. My heart rate often drops to 30 BPM while sleeping. It is usually in the low to mid 40's during the day. Freaked him out.