The old adage,“You are what you eat,”is not always reliable, as demonstrated in this mixed-longitudinal study of men that began in 1969. Mean values of percent body fat, total body potassium (TBK), and total serum cholesterol (SCHOL) did not show changes that correlated with any studied nutrient from repeated 4-day diet records. Mean blood pressure increased with increased body weight as age increased. High-density lipoprotein cholesterol decreased when polyunsaturated fat intake increased. The men had decreased mean height, TBK and increase in percent body fat as age increased. Food energy intake decreased equally from carbohydrates, protein and fat as age increased. Large standard deviations of mean values of measured parameters document heterogeneity of these subjects. A subset of 144 male cohorts was studied serially for 20 years in time-age, cross-sectional and longitudinal series. As they aged, height and TBK decreased (p