Summary Objective: To verify the knowledge about food and nutrition and its association with the nutritional status of obese patients with noncommunicable diseases (NCDs), and to identify the relationship between information sources and level of knowledge. Method: Cross-sectional study that included 263 outpatients of a cardiology referral hospital in Porto Alegre, Rio Grande do Sul, Brazil. The participants filled out a questionnaire on socioeconomic data and knowledge about food and nutrition and had their nutritional status evaluated by body mass index (BMI), waist circumference (WC) and waist-hip ratio (WHR). Results: BMI showed a significant inverse association with the percentage of correct answers (p=0.002), as well as WC (p=0.000) and WHR (p<0.001). This was also true for education (p<0.001) and female gender (p=0.005) compared to males. More than 60% of patients reported using television and 23% reported using newspaper as sources of nutritional information. Conclusion: Our study revealed a significant association between BMI and the level of knowledge about foods, showing that there is need for more information on obesity-related NCDs for greater understanding by patients.