Dietary Weight Loss Decreases Serum Angiotensin-Converting Enzyme Activity in Obese Adults

Objective: To study the effect of dietary weight loss, postural change, and an oral glucose load on serum angiotensin-converting enzyme (ACE) activity in obese adults. Research Methods and Procedures: Sixteen obese adult men and women with a mean body mass index of 35.7 ± 4.3 kg/m² were studied after 1 week on a maintenance energy lead-in diet and after 5 weeks on an identical but 40% reduced-energy diet provided by the General Clinical Research Center (GCRC). ACE activity was measured spectrophotometrically. Plasma renin activity and serum aldosterone were measured by radioimmunoassay. Results: All subjects lost weight, with a mean decrease in body weight of 7.0 ± 2.1 kg or 6 ± 3% of initial body weight (p < 0.00001). Systolic and diastolic blood pressure, supine plasma renin activity, and serum aldosterone levels decreased with weight loss (p < 0.05). Supine ACE activity decreased 23 ± 12% with weight loss (p < 0.00001). Standing ACE activity, which was significantly higher than supine ACE activity before and after weight loss (p < 0.05), also decreased 18 ± 17% with weight loss (p = 0.0007). A 75-g oral glucose load had no effect on serum ACE activity over a 3-hour period. Discussion: In obese adults, serum ACE activity declines with modest weight loss, increases with postural change, and is unaffected by an oral glucose load.