Blood pressure, electrolytes, and body size: their relationships in young relatives of men with essential hypertension

Blood pressure, body composition, and fat tissue cellularity in adults

While total body mass has been recognized for many years as having a strong positive association with blood pressure, it is not known whether body mass per se is important in this association or if a component of total mass, such as lean body mass or total body fat, is responsible for the relationship. To determine the relative importance of these components, 217 healthy adults unselected with respect to blood pressure or body composition, who were 18 to 49 years of age (X +/- sd = 33.1 +/- 8.9 years) had body density measured by underwater weighing. Body density was used to estimate percent body fat from which lean body mass and total body fat mass were determined. In addition, an adipose tissue biopsy from the gluteal area was made, and average fat cell size was measured using the osmium tetroxide method; fat cell number was then estimated. In both males and females, after adjusting for age, there were highly significant, positive partial correlations (r = 0.2 to 0.3) between measures of blood pressure (systolic, diastolic, and mean arterial) and percent body fat, total body fat mass or fat cell number. No significant correlation existed between lean body mass or fat cell size and any measure of blood pressure. These findings suggest that fat mass as opposed to body mass, per se, may be an important etiological component in elevated blood pressure in adults.

Hypertension in obese patients: hemodynamic and volume studies

Distinct hemodynamic and volume characteristics have been suggested for established hypertension in severe obesity, namely, a high cardiac output, and expanded blood volume, and a normal peripheral resistance. To evaluate whether hypertension in moderately obese patients represents a separate entity that can be defined by hemodynamic and volume profiles, we studied these in 50 such patients and compared results with those obtained in 59 nonobese essential hypertensives and 25 normal subjects. Both obese and nonobese hypertensives had a normal cardiac index (men, 2.8 +/- 0.1 vs 2.8 +/- 0.09 liter/min/m2; women, 2.9 +/- 0.1 vs 2.8 +/- 0.1 liter/min/m2, respectively) and similarly elevated total peripheral resistance (men, 47.1 +/- 2.3 vs 46.5 +/- 1.9 U . m2; women, 45.0 +/- 2.4 vs 44.0 +/- 1.3 U . m2, respectively) as compared to normals (cardiac index: men, 2.9 +/- 0.09 liter/min/m2, women, 3.4 +/- 0.2 liter/min/m2; total peripheral resistance: men, 29.4 +/- 1.0 U . m2, women, 28.3 +/- 2.8 U. m2). Volume measurements corrected to body surface area showed that both obese and nonobese hypertensive patients had lower blood volume (men, 2.6 +/- 0.05 vs 2.5 +/- 0.05 liter/m2; women, 2.2 +/- 0.05 vs 2.3 +/- 0.05 liter/m2, respectively) than normals (men, 2.9 +/- 0.08 liter/m2; women, 2.5 +/- 0.08 liter/m2). The results of this study suggest that hypertension in moderately obese subjects is similar in its hemodynamic and volume profiles to hypertension in the nonobese and that the presence of obesity does not alter the hemodynamic characteristics of established essential hypertension.

Obesity, sodium intake, and blood pressure in adolescents

It has been postulated that increased dietary sodium associated with greater food intake by obese people is a mechanism for the relationship between obesity and blood pressure (BP). We have evaluated this hypothesis by exploring the interrelationships of measures of obesity, sodium intake, and BP in 248 "normal" adolescents, 16 to 17 years of age. As an index of sodium intake, the sodium excretion in three overnight urine collections was used. As a more specific index of saltiness of diet, we used a ratio of sodium excretion to calorie intake, with calories estimated from 3-day diet records and dietary interview. Body weight and other measures of obesity showed a positive relationship with systolic blood pressure (SBP), but not with diastolic (K5) blood pressure (DBP5). Measures of overnight sodium excretion were positively correlated with body weight and calculated body fat percentage, suggesting that heavier people indeed ingest more sodium. This may result not from increased intake of food per se, but from increased saltiness of diet, since calorie intake did not increase with body weight. No significant relationships were found between BP and concurrent measures of sodium excretion or diet saltiness.