This practical guide is intended for professionals in the catering industry who wish to engage in a process to reduce food waste. It follows a diagnosis carried out in the company restaurants of five towers in the Parisian business district of Paris La Défense. The guide presents the conclusions of this study, as well as the solutions proposed to reduce food waste upstream and downstream of the supply chain. While food waste in France represents 10 million tonnes of losses every year, including 1.5 million tonnes in collective and commercial catering, sharing good practices and implementing collective actions are more necessary than ever. This innovative and pioneering initiative in a business district was led by the association La Défense des Aliments, founded by Allianz, Arpège, Eurest, Mazars and SUEZ and supported by the Paris La Défense public institution.