T B Van Itallie

The relative contribution of body fat and fat pattern to blood pressure level.

Although the association between body weight and blood pressure is irrefutable, body fat mass and blood pressure level may not necessarily be directly related. To clarify the relative contribution of fat mass to blood pressure level, we analyzed data on 399 adults consecutively entering a weight control program. Although most subjects were notably overweight (mean ideal body weight 177%), the population represented a wide spectrum of body weights and blood pressure levels. Study parameters included body fat mass (by total body water, 40K, and Steinkamp formula), lean body mass, body build (chest to height ratio), fat cell number and size from bilateral buttock biopsy specimens, upper fat pattern by arm to thigh circumference ratio, and central fat pattern by subscapular to triceps skinfold ratio. Our results concurred with previously noted correlations between obesity and blood pressure (as mean arterial pressure): weight (r = 0.44), percentage of body fat (r = 0.19), and absolute fat mass (r = 0.38; all p less than 0.01); however, lean body mass, age, and body build correlated highly with both fat mass and mean arterial pressure, thereby confounding this relationship. Multivariate analysis was performed to evaluate the relative contribution of fat mass to mean arterial pressure in the presence of these and other potentially confounding variables. Lean body mass, age, body build, and an upper body fat pattern were found to contribute significantly to the variation in mean arterial pressure (p less than 0.01). In their presence, percentage of body fat, absolute fat mass, central fat pattern, fat cell characteristics, and age of onset of obesity did not significantly improve the predictability of mean arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiology of energy intake: an inventory control model.

An inventory control model is used to describe the regulation of depot fat and contribution made to the satiation process by putative feedback signals. In the two bin inventory control system, adipose tissue is viewed as a large storage reservoir which is periodically refilled by means of adjustments made in meal consumption. The gastrointestinal tract is viewed as a smaller bin which triggers renewed food ingestion when it becomes partially emptied. However, reduction in the contents of the adipose tissue bin below a critical level (reorder point quantity) generates a signal to the brain that appropriately modulates meal size and intermeal interval. Because this model evolved to cope with worst case situations, a strong bias for storage in time of plenty is inherent in the system. This fact helps to account for the high prevalence of obesity in energy-rich societies, where, in contrast to the situation that obtains in primitive societies, the energy cost of obtaining food is minimal.

Appraisal of excess calories as a factor in the causation of disease

The ingestion of a diet higher in caloric content than is required for energy needs leads to energy storage; this is accomplished by the deposition of triglycerides in adipose tissue. There is no clear evidence that the metabolic burden of excess calories is in any way hazardous to health except insofar as it leads to weight gain and eventually to obesity. Some studies show that a high caloric intake coupled with physical exertion that is sufficiently increased to maintain energy balance may be more beneficial to health than is a lower caloric intake balanced by a reduction in physical activity. Caloric intake and physical activity are so interrelated that it is impossible to gauge the effects of one independently of the other.