Relying on data derived from medical records of past visits to a physician, patients' charts were examined to evaluate the effectiveness of a single nutrition counseling session provided by the same registered dietitian in improving outcome measures for patients with type 2 diabetes mellitus or cardiovascular disease. This was a retrospective study of 175 patients' charts from which laboratory data were extracted before and at 3 months after seeing the dietitian. Records were categorized into two groups based on whether the patient had attended or not attended a single nutrition counseling session. At 3 months, the group that received the nutrition counseling had statistically significant improvements in blood values and body mass index compared with the group that did not receive nutrition counseling. This study further confirms the value of a single nutrition counseling session as an effective approach to treating type 2 diabetes and cardiovascular disease.