The Effect of Weight Loss on the Sensitivity of Blood Pressure to Sodium in Obese Adolescents

TLDR

The study aimed to determine how sodium intake affects blood pressure regulation in obese versus nonobese adolescents by measuring BP after high‑ and low‑salt diets. Blood pressure was measured in obese and nonobese adolescents after two‑week high‑ and low‑salt diets, and 51 obese participants were re‑evaluated before and after a 20‑week weight‑loss program. Obese adolescents exhibited a markedly greater drop in mean arterial pressure when switching from high‑ to low‑salt diets compared to nonobese peers, and sodium sensitivity was best predicted by fasting insulin, aldosterone during low salt, norepinephrine during high salt, and body‑fat percentage; weight loss reduced sensitivity in those who lost more than 1 kg, while the remaining subjects remained sensitive, supporting the role of hyperinsulinemia, hyperaldosteronism, and sympathetic activation in obesity‑related BP sodium sensitivity. N Engl J Med 1989; 321:580–5.

Abstract

To clarify the role of sodium intake in the regulation of blood pressure in obese subjects, we measured blood pressure in 60 obese and 18 nonobese adolescents after successive two-week periods of a high-salt diet (>250 mmol of sodium per day) and a low-salt diet (<30 mmol per day). When they were changed from a high-salt to a low-salt diet, the obese group had a significantly larger mean change (±SE) in mean arterial pressure (-12±1 mm Hg) than did the nonobese group (+1±2 mm Hg; P<0.001). The variables that best predicted the degree of sodium sensitivity were the fasting plasma insulin level, the plasma aldosterone level while the low-salt diet was being given, the plasma norepinephrine level while the high-salt diet was being given, and the percentage of body weight made up by fat. Fifty-one of the obese adolescents were also studied before and after a 20-week weight-loss program. After the weight-loss program, the 36 subjects who lost more than 1 kg of body weight had a reduced sensitivity of blood pressure to sodium (difference from value during high-salt diet to that during low-salt diet, -1±1 mm Hg). The blood pressure of the remaining 15 adolescents was still sensitive to sodium intake (-11±3 mm Hg). These results support the hypothesis that the blood pressure of obese adolescents is sensitive to dietary sodium intake and that this sensitivity may be due to the combined effects of the hyperinsulinemia, hyperaldosteronism, and increased activity of the sympathetic nervous system that are characteristic of obesity. (N Engl J Med 1989; 321:580–5.)