Abstract Background Obesity is a non-communicable chronic disease which carries a high cost for the Brazilian Unified Health System. Standardized protocols can help primary health care (PHC) professionals manage the disease. Objectives To describe the validation process of a protocol concerning dietary guidelines for adults with obesity in PHC by non-nutrition professionals. Methods A validation study of a dietary advice protocol consisting of 6 recommendations was conducted according to Brazilian Dietary Guidelines. The topics incorporated into the recommendations were submitted to a panel of judges for content validity and achieved a Scale Content Validity Index (S-CVI) score >0.80. Subsequently, an online workshop was held and consisted of guiding questions to adequately improve current protocols. Face validity was assessed in a mediation workshop conducted with PHC non-nutrition professionals. Following the validation process, necessary adjustments were made to the eating protocol. Results The validation process was conducted by a panel of 20 judges and 10 PHC professionals. The content was validated using a 0.98 S-CVI. The online workshop expert panel agreed the instrument provides a trustworthy foundation for appropriate dietary guidelines. Moreover, the judges suggested changes to the flowchart designed to support the professionals’ decisions, discussed the absence of quantitative prescription guidelines, and offered additional suggestions to strengthen equity and encourage autonomy in non-nutrition healthcare professionals in PHC. Conclusion This study describes the validation process of a dietary advice protocol for people with obesity, as well as the importance of its integration into PHC.