But, clearly proud of her toned physique, the 21-year-old actress decided to wear a pink sports bra and very low-slung leggings to display her toned midriff as she hit the gym.
Emma teamed her exercise clothes with a grey jumper tied around her waist and a headband to keep her hair out of her eyes.
Toned: Emma Watson showed off her flat stomach in a pink crop top and low-slung leggings as she hit the gym in Pittsburgh yesterday
Athletic: Emma, who is in Pittsburgh to film her new movie, has been keeping busy with regular trips to the gym
And as well as staying healthy physically, Emma also seemed to be keen to remain emotionally sound, and was spotted carrying a copy of the self-help book A 3rd Helping of Chicken Soup for the Soul as she left the gym after her workout.
Book worm: Emma was reading A 3rd Helping of Chicken Soup for the Soul
Emma has clearly been working hard on her physique, with not an inch of fat to be seen on her lean figure as she headed back to her temporary home in Pittsburgh yesterday.
However, talking about her figure recently, Emma said staying slim isn't something she constantly worries about - she is more concerned about staying healthy.
In a recent inerview, Emma said: 'It's just not something that I aspire to, to be super-skinny. It's not inspirational at all for me.
'I'm lucky that I'm this size naturally. I don't diet...I love chocolate and pasta and I love baking.
'I make a great raspberry amaretto cake!
'There is so much pressure on girls our age to be smart and pretty and funny and skinny - they have to be everything.
'I definitely know what that pressure is like, but my philosophy is to eat what you like and be healthy and exercise.'
Emma is in Pittsburgh working on her latest film The Perks Of Being A Wallflower.
She plays high school senior Sam in the film, adapted from the 1999 book by Stephen Chbosky.
Sam and step-brother Patrick take protagonist Charlie under their wings and expose him to their hard-partying, drug-fuelled world.
The hard-hitting storyline deals with suicide, abortion, homosexuality and child abuse, and the film is slated for release next year.
Fashionista: Emma recently topped a best-dressed poll thanks to her red carpet outfit choices, seen here left at the BAFTAs in February, and right at the most recent Harry Potter premiere last year
Screen star: Emma as Hermione Granger with Daniel Radcliffe as Harry Potter and Rupert Grint as Ron Weasley in Harry Potter And The Deathly Hallows: Part 1