I keep reading that a person should aim to lose no more than 2 lbs. per week but what if they're REALLY fat?

I mean, geez, should some guy that weighs 400 or some woman who weighs 300 be satisifed with just losing 2 lbs? Isn't there some sliding scale? Maybe if you're 50 lbs or less over your ideal weight then, yes, lose 2 lbs. per week but if you're 51 to 100 lbs over your ideal weight try for 2.5 lbs for week and if you're 101 to 150 lbs. overweight then try for 3 lbs. per week?