This chapter discusses the case of a 32 years old single mother working part time, Wendy, who changed from a vegetarian diet, to a vegan diet. She was very active, walking her daughter to and from school daily, which is 3 miles away, making a total of 12 miles a day. She also attended ballet classes once a week. At her own request, she was referred by her GP, following a recent diagnosis of rheumatoid arthritis (RA). She suffered from anorexia when she was 16 years old, but is in remission and managing well although she remains anxious about her weight. The questions raised in this chapter include queries regarding the definition of a vegan diet, nutrition and dietetic diagnosis, whether Wendy's body mass index (BMI) is cause for concern, and whether the discussions with Wendy need to be informed to her GP.