The One Direction hunk is on the currently on the American leg of the band's 'Take Me Home' world tour and has banned all sweets and cakes from his tour bus in a bid to get into shape.
One Direction's fitness trainer Mark Jarvis told the Daily Star newspaper: "He is keen to ditch all the cakes and sweets. His favourite is black forest gateau."
The 19-year-old singer - who is joined in the group by Niall Horan, Zayn Malik, Liam Payne and Louis Tomlinson - is obsessed with a "healthy ice cream" named Wheyhey, which is a sugar-free protein-enriched product that is a favourite among sports men who follow calorie controlled diets.
Mark added: "The lads want to get defined beach bodies. Lots of protein is the best way for them to get in shape and build up muscle.
"Harry has heard about this new healthy ice cream and is really fascinated by it. He has requested boxes of it to be flown over as he has a real sweet tooth."
Harry has been spotted working out with his fellow fitness conscious bandmate Niall in the gym and the pair have been seen out jogging together too.