The 1.65-metre (5.4-foot) tall 21-year-old, identified only by her first name, Francesca, was considered unsuitable for the army as her 78.5 kilos (173 pounds) was "incompatible with the parametres of physical aptitude of military service", it said.
She had argued before an administrative tribunal in the central coastal city of Ancona that she had passed her first army medical, but then put on weight during her first 10 months of training due to the stodgy food served.
But her argument did not hold weight with the court, which said that she had failed to lose her surplus kilos during a convalescence period given her by the military go to on a diet.
However, her lawyer said on Tuesday she was not going to take the matter lightly, and that she would appeal the ruling.
He said that for Francesca, who hails from Catania in Sicily, "the army was her choice of lifestyle and a work opportunity.
"I don't think that all the military you come across in Italy have perfect figures," he said.
The woman joined the Ascoli Piceno regiment near Anconi in 2001.
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