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John admits he worries for the "frail" 26-year-old pop star, who is godmother to his son Zachary, as she travels the world on her Born This Way Ball tour.
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He tells The Guardian Weekend magazine, "I look at Gaga and I think, 'How does she do it?' I talk to her mom and dad about it. They worry.
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"She is frail, and she doesn't eat when she should do, and she's a girl, and it's tougher for a girl. She works really hard. She will be in Denmark one night and Saudi Arabia the next. I know how tiny she is and I do worry about her, yes."