Ermanno Lanzola

Obesity, Diet and Body Temperature

Studies conducted thus far on the pathogenesis of obesity have not clearly determined the role of body temperature in the energy balance. In an attempt to explore this relationship further, research has been undertaken, a part of which is represented by the present investigation carried out on 22 adult males: 11 having a BMI less than or equal to 25 (group A) and 11 with BMI greater than 25 (group B). Body temperature was measured by mouth and on the skin surface (in 4 points according to Ramanathan) on 2 consecutive days (every 30 min from noon to 6:30 p.m.), the 1st day with the participants fasting and the 2nd day after consumption of a meal whose energy content represented a part (45%) of the 24-hour energy intake of the subjects, as previously ascertained by a survey of their food consumption. The study was carried out under frequently checked microclimatic conditions. During the week prior to the measurements, the alimentary consumption of the subjects was monitored by direct weighing for 5 consecutive days. A significant rise in body temperature, probably due to dietary thermogenesis, was observed in group A (internal temperature: F = 13.05; skin temperature: F = 6.48) as well as in group B (internal temperature: F = 24.88; skin temperature: F = 5.35) after the meal. However in group B the skin temperature showed a smaller increase than in group A (delta t degree 0.31 vs. 0.49) and an earlier trend towards the basal values (nearly 5 vs. 6 h after the meal). In both groups a decrease in the skin delta t degrees is evident at 3 and 3.5 h, respectively, after the meal, followed by a more remarkable increase in this difference between the 4th and the 5th hour. The meaning of this decrease as well as the difference in body temperature versus caloric intake is discussed. Normal weight individuals demonstrated a positive correlation (r = 0.83) between usual caloric intake per square meter of body surface and fasting internal body temperature. This correlation was not observed in subjects with BMI greater than 25.

Effects of Various Dietary Selenium Intakes on the Levels of Blood Glutathione-Peroxidase and Selenium in Long-Term Fed Rats

Female Sprague-Dawley rats were fed a torula diet or wheat diets containing 4 levels of Se partially supplemented (24-402 ppb) for 120 days. Selenium content and glutathione-peroxidase (GSH-Px) activity in plasma and erythrocytes were measured every 20 days. In rats fed torula diet or basal wheat diet, plasma Se (P-Se) increased for up to 60 days, then remained constant, while erythrocytes Se (E-Se) and E-GSH-Px decreased in basal-diet rats during the first 40-60 days, then increased. In rats fed supplemented diets, P-Se and P-GSH-Px increased more rapidly than E-Se and E-GSH-Px, plateauing at 60-80 days. The best correlation was found between P-GSH-Px and dietary Se indicating that this index is the most sensitive for evaluating changes resulting from different Se intakes. In addition, correlations became more significant with time. The results from rats fed a low Se diet suggest the existence of regulatory mechanisms working in different ways and at different times in plasma and erythrocytes.

Skin Temperature and Energy Expenditure

The value of mean skin temperature as an estimate of energy expenditure was verified in a sample of 10 normal-weight adult male subjects. Measurements were carried out with thermometric probes under conditions of rest and environmental thermoneutrality. Total heat losses were then calculated through a computerized complex mathematical formula. The value for mean energy expenditure obtained in this manner (100.2 +/- 7.02 kcal/h) is extremely close to the value for theoretical metabolism derived from the predictive equations in the literature (95.01 +/- 6.14). This verification of the validity of transforming cutaneous temperature data into energy expenditure, in accurately standardized experimental conditions, confirms the importance that the value of mean skin temperature, in the area of variability among individuals, can have in conditioning the energy balance at different levels, for a given caloric intake and with all other parameters being equal (age, sex, physical activity). In this connection, these results suggest that skin temperature may play a role in the pathogenesis of obesity.