Background: Patients with serious mental illness (SMI) are more likely to have Type 2 diabetes mellitus (T2DM). However, studies that discuss the eating habits of patients with both T2DM and SMI are lacking.

Purpose: This study was designed to explore the beliefs and experiences of Taiwanese patients with SMI who also have T2DM.

Methods: Fieldwork for this study included 2 years of participant observation and individual interviews with 13 patients with SMI. Data from transcripts of observational field notes and interviews were transcribed verbatim and analyzed.

Results: The participants described their experiences and concerns regarding dietary management during the period after receiving their T2DM diagnosis. The results of the data analysis were distinguished into three categories, including (a) increased difficulty in life, (b) positive view of dietary control, and (c) inability to abide by dietary restrictions.

Conclusions: The findings suggest that healthcare professionals should work to better understand the challenges faced by patients with SMI and T2DM in implementing changes and resisting the temptation to eat unhealthy food and provide suggestions tailored to their cultural background, lifestyle, and eating characteristics.