Background To investigate the relationship of fast food consumption with cognitive and metabolic function of adults (18–25 years old) in Riyadh, Kingdom of Saudi Arabia. Materials and Method This cross-sectional study was conducted at the College of Medicine at King Khalid University Hospital, Riyadh, Saudi Arabia. The conventionally recruited subjects underwent an evaluation that included demographic data, quality of life (wellness, stress, sleepiness, and physical activity), mini-mental status examination, and the frequency of fast food consumption. To investigate metabolic function, blood was drawn to evaluate serum HDL, LDL, cholesterol, and triglyceride levels. Cognitive function was assessed by the Cambridge neuropsychological test automated battery. The participants were divided into 2 groups based on fast food consumption: those who consumed fast food 3 times per week or less (Group 1) and those who consumed fast food more than 3 times per week (Group 2). Results The mean diastolic blood pressure in Group 1 and Group 2 was 72 mmHg and 77 mmHg, respectively, a significant difference (p = 0.04). There was no significant difference for cognitive function and quality of life between the two groups. There was significant correlation of HDL with AST correct mean latency and the AST correct mean latency congruent (p = 0.02, p = 0.01, respectively) and TC with diastolic blood pressure (p = 0.003). Conclusions We concluded that fast food consumption has an effect on blood pressure but has no direct effect on cognition or quality of life.