I disagree with your doctor as well.
There is the thing about eating more in the morning, and having the chance to "burn it off all day", but that really isn't how it works. Think of it in terms of your activity, rather than your diet:
If you do the same physical activity ever week (the same amount of exercise, live teh saem lfiestyle, go to the same job and fufill the same duties, etc.) then you are burning the same amount of calories each day-it wouldn't really make a difference if you worked first shift and did your workout in the afternoon, or if you worked second shift doing the same exact thing, and did the same workout in the morning instead. You are burning the same amount of calories each day.
If you are eating 1200, or 1400, or 1600 calories a day-or whatever it is that you do-you are still eating that same amount of calories per day...no matter WHEN they are eaten. 1400 calories is 1400 calories a day-no matter what.
I, also, would go nuts eating only 3x a day. If you are eating the same amount calorie wise-it really doesn't make that much difference if you eat it in 3 meals a day, or 3 smaller meals and a healthy snack or two. You can still eat often, and eat the same amount-if you eat smaller meals and snacks. I personally think that for me, eating smaller meals and snacks more often works better-since I like to munch. I don't get ravenous and start rummaging the cabinets and fridge for anything and everything.