The major goal of this study was to determine if the elevated blood pressures in obese men < 45 years old with mild hypertension persist outside the clinic. A secondary aim was to determine if hyperinsulinemia is associated with accentuated diurnal changes of blood pressure. To address these objectives, the clinic and ambulatory blood pressures as well as a 75-g, 2-h oral glucose tolerance test measurements were obtained from 9 lean normotensive, 9 lean hypertensive, and 22 obese hypertensive men < 45 years old. The week before study, volunteers ate an isocaloric diet with 220 mEq of NaCl/day. Obese hypertensives, subdivided by high (n = 11) and low (n = 11) insulin areas-under-the-curve (AUCs) in response to oral glucose, and lean hypertensives maintained higher ambulatory blood pressure than lean normotensives (130 +/- 3/74 +/- 1, 136 +/- 4/78 +/- 2, 132 +/- 5/77 +/- 3 v 118 +/- 4/65 +/- 2 mm Hg, respectively, P < .05). As expected, the insulin AUC during the glucose tolerance test was higher in obese hypertensives with higher insulin AUCs than in obese hypertensives with lower insulin AUCs, lean hypertensives, or lean normotensives (13.9 +/- 1.2 v 7.9 +/- 0.3, 7.2 +/- 0.7, 5.7 +/- 0.7 mU-min/dL, P < .05). Insulin AUCs were not significantly different in obese hypertensives with lower insulin levels, lean hypertensives, or lean normotensives. The diurnal increases of systolic and diastolic blood pressure as well as heart rate and pressure-rate product were similar in all four groups.(ABSTRACT TRUNCATED AT 250 WORDS)