In this study, the effect of weight loss on blood pressure and various facets of glucose and insulin metabolism was examined in 22 subjects with mild to moderate obesity; 11 with high blood pressure (diastolic blood pressure > 95 mm Hg) and 11 with normal blood pressure (diastolic blood pressure < 90 mm Hg). The two groups were similar in mean (+/- SEM) body mass index at baseline (30.2 +/- 1.0 v 31.6 +/- 1.1 kg/m2), and each group lost approximately 8 kg during the 3-month study period. Blood pressure fell significantly (P < .003) following the 8 kg weight loss in both the normotensive (122 +/- 3/81 +/- 3 to 110 +/- 3/74 +/- 2 mm Hg) and hypertensive (149 +/- 3/98 +/- 1 to 135 +/- 3/86 mm Hg) subjects. Furthermore, the plasma glucose and insulin responses to a 75 g oral glucose load were significantly lower (P < .001) following weight loss. Finally, insulin resistance, as assessed by determining the steady-state plasma glucose (SSPG) concentration at the end of a 180 min infusion of somatostatin, insulin, and glucose, was also lower (P < .002) after the 8 kg weight loss in the normotensive (243 +/- 23 to 172 +/- 15 mg/dL) and hypertensive subjects (266 +/- 18 to 181 +/- 25 mg/dL). Since the steady-state plasma insulin concentrations were, if anything, slightly lower after weight loss in both groups, the lower post-weight loss SSPG values actually underestimate the improvement of insulin resistance. Thus, weight loss of 8 kg in moderately obese individuals leads to significant decreases in blood pressure and plasma glucose and insulin concentrations in response to an oral glucose challenge and degree of insulin resistance.