Original slimming factor Weight Loss Ever Be Healthy? Or Permanent?

When people answer questions about weight loss on the internet, they suddenly become all-knowing. This effect is especially noticeable when the question involves rapid weight loss or 'crash dieting'. Some examples from yahoo answers are:
"There is no such thing as losing fat fast."
"Any weight you lose that quickly is just water weight, not fat and you will not look noticeably different"
"You should only be losing about 2 lbs a week. Anything more is unhealthy,"
"You will gain all the weight back (and maybe more) when you reach your target weight and start eating normally"
But what make these people so confident in their answers? Why can't you lose fat faster than 2lb a week? Why do you have to gain all that weight back? Why is it so unhealthy?
Original slimming factor
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