I am sure this joke was your inspiration about that one!
A white guy married a Pakistani girl. He was learning Urdu as well. Once she was talking to her friend, and the friend used the word "Kambakhat".. He asked his wife what it means, she thought its a good idea not to tell him actual meaning so that he don't get bad impression of Pakistani's. She told him, it means fat. Few days later, she was talking with her friend in front of him again, friend used the word "manhoos".. Again he asked what manhoos means. She again felt ashamed telling the truth and told that it means slim.
Anyways, few days later, his mother in law came to visit them. He said to her:
"Pehlay tou aap barri kambakhat thein, ab itni manhoos kaisay hogaeen?"