Why couldn’t the man put on more weight?

F:  Henry, why? You look so worried?
M: It’s my weight. I have been one kilogram thinner recently. I don’t know what is wrong. I keep on eating and eating to put on a little weight, but it simply doesn’t work !
F: I think the most important thing is that you should keep a good mood, take everything easy and everything will be OK, including your weight.
M: Hey, Laura, don’t you feel worded about your weight? You are getting more and more plump.
F: As a matter of fact, I don’t worry about it.
M: It seems that there are too many differences between you and me.
F:  Yes. And I guess there are actually too many differences between thin people and fat people.
M: For example?
F:  For example, thin people believe in logic. Fat people see all sides. The sides fat people see are rounded blobs, usually gray, always not clear and truly not worth worrying about.
M: But thin people persist. We always have a long list of logical things ready to tell other people.
F:  But we fat people are much nicer. We smile all day. We know all about the mystery of life.
M: We thin people, however, like to make plans. Sometimes our programs seem too dull, too hard, too off the mark to many people.
F:  We fat people like enjoying life. We are generous, giving, and gallant.
M: Oh, I wish I could become a nice fat guy instead of a mean thin one.