"Losing weight" joke

Two guys are in a bar and the guy says to his friend, "I wanna lose 10 pounds."
His friend says, "Okay give me one hundred dollars."
The guy gives him the money and leaves the bar.
A day later a hot chick is in the guy's front yard. She says, "If you can catch me, I will have sex with you."
The guy chases her around for an hour and loses 10 pounds.
The next day a guy tells the first guy's friend, "I wanna lose 20 pounds."
The friend says, "Okay give me two hundred dollars."
The second guy gives the friend the money and leaves.
The next day a hot chick is in the second guy's yard.
She says, "If you can catch me you can have sex with me."
The second guy chases her around for two hours and loses 20 pounds.
The next day a fast olympic athlete tells the guys' friend he wants to lose 30 pounds.
The guys' friend thinks and then finally says, "Okay give me three hundred dollars."
The athlete gives him the money and leaves.
The next day there's a 10 foot tall, male gorilla in his yard with a sign that says, "If I catch you, you have to have sex with me."