At the turn of the xixth and xxth centuries, whereas meat consumption was supported by mainstream medicine and becoming widespread in Western societies, the French and Belgian vegetarian movement evolving in vegetarian circles led by physicians and hygienists was trying to prove scientifically the physical and ethical benefits of a vegetarian diet. This paper deals with the methods that were chosen to offer scientific evidence, in spite of the controversial nature of such results, by focusing on three inquiries whose authors, whether men or women, diverge in their dealings with the scientific field and the vegetarian movement. The paper also shows that the medical inquiry is a fairly adaptable form integrating physiological, experimental and social data, which makes it a relevant tool for the vegetarian movement self-appropriation in order to enhance its legitimacy, especially in the field of social reform. h