This study validated further the bioelectrical impedance analysis (BIA) method for body composition estimation. At four laboratories densitometrically-determined lean body mass (LBMd) was compared with BIA in 1567 adults (1069 men, 498 women) aged 17-62 y and with 3-56% body fat. Equations for predicting LBMd from resistance measured by BIA, height, weight, and age were obtained for the men and women. Application of each equation to the data from the other labs yielded small reductions in R values and small increases in SEEs. Some regression coefficients differed among labs but these differences were eliminated after adjustment for differences among labs in the subjects' body fatness. All data were pooled to derive fatness-specific equations for predicting LBMd: the resulting R values ranged from 0.907 to 0.952 with SEEs of 1.97-3.03 kg. These results confirm the validity of BIA and indicate that the precision of predicting LBM from impedance can be enhanced by sex- and fatness-specific equations.

The second National Health and Nutrition Examination Survey found that 26% of U.S. adults, or about 34 million people aged 20 to 75 years, are overweight. The survey used a body mass index of 27.8 kg/m2 or greater for men and 27.3 or greater for women to define overweight. Prevalence of overweight increases with advancing age and is generally much higher among black women than among white women. Women below the poverty line have a much higher prevalence of overweight between ages 25 and 55 years than women above the poverty line. Multivariate analysis indicates that for women race and poverty status are independent predictors of overweight. Hypertension, hypercholesterolemia, and diabetes are commoner in overweight persons than in persons who are not overweight. The relative risk of hypertension, hypercholesterolemia, and diabetes is greater in overweight adults aged 20 to 45 years than it is in overweight persons aged 45 to 75 years. This observation is consonant with mortality data, suggesting that being overweight during early adult life is more dangerous than a similar degree of overweight in later adult life.

This study 1) further validated the relationship between total body electrical conductivity (TOBEC) and densitometrically determined lean body mass (LBMd) and 2) compared with existing body composition techniques (densitometry, total body water, total body potassium, and anthropometry) two new electrical methods for the estimation of LBM: TOBEC, a uniform current induction method, and bioelectrical impedance analysis (BIA), a localized current injection method. In a sample of 75 male and female subjects ranging from 4.9 to 54.9% body fat the correlation between LBMd and LBM predicted from TOBEC by use of a previously developed regression equation was extremely strong (r = 0.962), thus confirming the validity of the TOBEC method. LBM predicted from BIA by use of prediction equations provided with the instrument also correlated with LBMd (r = 0.912) but overestimated LBM compared with LBMd in obese subjects. However, no such systematic error was apparent when new prediction equations derived from this heterogeneous sample of subjects were applied. Thus the TOBEC and BIA methods, which are based on the differing electrical properties of lean tissue and fat and which are convenient, rapid, and safe, correlate well with more cumbersome human body composition techniques.

Resting metabolic rate (RMR) was measured in 154 women and 48 men before the beginning of a weight reduction program. In both sexes there were significant univariate correlations between RMR and fat-free mass, body fat, weight, fat cell weight, and fat cell number (from total body water). Women also showed significant correlations between RMR and fat cell number (from total body potassium), free triiodothyronine index, and fasting and postglucose insulin levels. Multiple regression analysis showed that both fat-free mass and fat cell weight and number were significant predictors of RMR. The contribution of fat-free mass was three to five times greater per kg than that of body fat. There was no significant contribution of thyroid hormones or insulin to the prediction of RMR. Fat cell number and fat cell weight were significant predictors of RMR, whether determined from body water, body potassium, or a formula using both water and potassium. There was no significant difference in regression coefficients between men and women. Thus the difference in RMR between the sexes is probably caused by the higher proportion of fat-free mass in men. The effect of age was small and not statistically significant.

A universal eating monitor has been developed that permits covert continuous weighing of a subject's plate or other food reservoir by means of a concealed electronic balance. By coupling the device with a digital computer, it is possible to record precisely the amount consumed every 3 s throughout a single-course meal consisting of a relatively homogeneous mixture of foods. The monitor have been used to compare total intake, meal duration, initial rate of intake, and deceleration of intake in human subjects ingesting either a solid or liquid version of the same food after 3 or 6 h without food. It was found that the liquid form was eaten faster than the solid form, but that total amounts consumed in each form were not significantly different. These results suggest that when the rate of consumption is controlled by the physical consistency of the food, the amount eaten is not determined by the rate of consumption alone. Further studied are necessary to determine the relative roles of visual cues and interoceptive signals on quantity eaten.