As shown in more than 8000 proband-parent pairs derived from a total-community sample and followed in longitudinal fashion, the 5-year incidence of obesity (new cases per 5-year period) approximates 8 percent for the juvenile-onset, adolescent-onset and adult-onset obese alike. Parents of juvenile-onset (ages 5-9), adolescent-onset (10-19) and adult-onset obese (20-39) tend to be of above-average fatness level, +0.25Z scores, overall, regardless of the age at onset of obesity in their progeny. Except for the parents of the juvenile-onset obese, educational level of the parents tends to be below average for the sample as a whole. These new data acquired in longitudinal context and explored in retrospective-prospective fashion do not substantiate the notion that different onset ages of obesity indicate separate etiologies and different family constellations.