In 1742 La Mettrie left his family and travelled to Paris, where he obtained the appointment of surgeon to the Gardes Françaises regiment, taking part in several battles during the War of the Austrian Succession.
1742. aastal jättis La Mettrie pere ning reisis Pariisi, kus ta määrati kirurgiks Gardes Francaises' rügementi ning võttis osa mitmest lahingust Austria sõjas.