Dietary assessment in Whitehall II: the influence of reporting bias on apparent socioeconomic variation in nutrient intakes.

OBJECTIVE: To assess socio-economic differences in nutrient intake, giving particular consideration to the influence of reporting bias. DESIGN: Cross-sectional study. Three methods of data analysis (inclusion of all subjects, exclusion of low energy reporters, and regression-based energy adjustment) were evaluated against biomarkers of fatty acid and antioxidant intakes. SETTING: London-based Civil Servants. SUBJECTS: Age and employment grade stratified random sub-sample of 459 men and 406 women aged 39-61 y who completed 7 d diet diaries at Phase 3 follow-up (1991-93) of the Whitehall II Study. DIETARY MEASURES: Mean daily intakes by employment grade (6 levels) of dietary energy, total fat, saturated fatty acids, polyunsaturated fatty acids (PUFA), linoleic acid, carbohydrate excluding fibre, dietary fibre, protein, alcohol, vitamin C, vitamin E, carotenes, potassium and calcium. Biomarkers: serum cholesterol ester fatty acids (CEFA), total cholesterol, plasma alpha-tocopherol and beta-carotene. RESULTS: Low energy reporting (LER), defined as a reported energy intake below 1.2 times calculated basal metabolic rate, was strongly associated with employment grade (top grade: men 17.3%, women 19.3%, bottom grade: men 45.7%, women 49.2% trend P < 0.0001 both sexes). This association is only to a small extent accounted for by the relative weight distribution across grades. The direct associations with grade--high status, high intakes--of total fat, saturated and polyunsaturated fatty acids seen in the results overall were greatly reduced or abolished when LER were excluded or when energy adjustment was used. Direct associations between grade and intakes of vitamin C and potassium in both sexes were evident regardless of data presentation method. Spearman correlations between biomarkers and reported intakes, for example CEFA and dietary linoleate (men 0.46, women 0.61), plasma beta-carotene/cholesterol ratio and dietary carotenes (men 0.16, women 0.21) together with theoretical considerations indicate that energy adjustment may be the preferred method for reducing the influence of reporting bias. CONCLUSIONS: Low energy reporting is a major source of bias in dietary surveys and its prevalence shows a marked inverse association with socio-economic status. The energy adjustment method provides an approach which reduces this bias without exclusion of low energy reporters. Intakes of micronutrients including vitamin C, rather than fatty acids, showed associations with socio-economic status consistent with a dietary explanation for social inequalities in cardiovascular disease.

Correlates of leukocyte counts in men.

Because of previously reported associations between a high leukocyte count and risk of ischemic heart disease (IHD), we examined the relation of leukocyte counts to various characteristics among 3591 white and 506 black 31- to 45-year-old men. The mean leukocyte count was approximately 1000 cells/microL higher among whites than among blacks, and approximately 1900 cells/microL higher among current smokers than among nonsmokers. The leukocyte count was also higher among men who had recently stopped smoking and among men who reported their general health as poor or fair. Independent of these relations, the leukocyte count was associated positively with the platelet count (r = 0.29), triglyceride level (r = 0.21), heart rate (r = 0.15), and use of corticosteroids and beta-blockers; and inversely with alcohol consumption and prothrombin time (r = -0.10). The examined characteristics could together account for 37% of the variability in leukocyte counts. These relatively strong associations indicate that it may be difficult to disentangle the relation of the leukocyte count to IHD from that of other risk factors.

Chronic fenfluramine treatment: effects on body weight, food intake and energy expenditure.

Fenfluramine suppressess the body weight of experimental animals during chronic treatment by a mechanism that is not yet clear. The present research investigated the contributions of fenfluramine-induced alterations in food intake and two components of energy expenditure, resting energy expenditure (REE) and the thermic effect of food (TEF), to maintenance of a lowered body weight in male Long Evans rats. DI-Fenfluramine (20 mg/kg) produced an initial severe anorexia and weight loss. Food intake then increased steadily, reaching control levels by the fourth day of treatment. Tolerance to the anorectic effects of fenfluramine was not complete however -- food intake of fenfluramine-treated rats fell below control levels on 7 of the remaining 20 days of treatment. The body weight of fenfluramine treated rats remained significantly below control levels throughout the entire treatment period, but rose rapidly to control levels following fenfluramine withdrawal. REE was unaffected by fenfluramine treatment. By contrast, fenfluramine treatment significantly altered the TEF. Twenty-four hours after initiation of treatment the TEF of fenfluramine treated animals was higher than that of controls. On the 15th day of drug administration and the first day of fenfluramine withdrawal, however, the TEF of control and treated animals no longer differed. By contrast, on the second day of fenfluramine withdrawal the TEF of fenfluramine treated rats was suppressed to 17% of control levels. These findings suggest that the effect of fenfluramine on body weight involves modulation of both food intake and energy expenditure.

Decline in delayed-type hypersensitivity response in obese women following weight reduction.

The effect of weight loss on immuno function was evaluated in 14 middle-aged obese women. Cutaneous delayed-type hypersensitivity to five recall antigens was measured before a weight loss of 21 kg and again after weight had been stabilized. Weight loss was associated with a decrease in both number and magnitude of delayed-type hypersensitivity responses. The number of positive skin tests decreased from 3.1 +/- 0.2 to 2.4 +/- 0.3 per subject, and the mean cutaneous induration size decreased by 38%. The decrease in induration size was positively correlated with the decrease in body mass index (r = 0.63), weight (r = 0.59), and fat mass (r = 0.52). These preliminary findings suggest that large weight losses may result in decreased expression of immune function.

The influence of obesity and its treatment on the immune system.

Obesity and weight reduction are significant public health concerns in the United States and other developed countries. Although much research has examined the adverse health consequences of overweight and the benefits of weight loss, the effects on immunologic function of either excess adiposity or weight reduction treatments for obesity have received relatively little attention. In general, studies of immunologic function in obese humans and experimental animals indicate that excess adiposity is associated with impairments in host defense mechanisms. Definitive studies of immune function in human obesity are, however, still needed. Preliminary investigations suggest that certain types of weight reduction strategies produce further alterations in immune responsiveness. More research is needed to confirm or refute these initial findings and to assess the long term consequences of weight loss for overweight individuals. Nutritional and neuroendocrine status are among the factors likely to be involved in modulation of immune responses in obesity and as a consequence of dieting and weight reduction.

Weight loss and body fat distribution: a feasibility study using computed tomography.

Computerized tomography (CT) was used to assess the effect of a loss of body weight (18.8 kg) on the size of five fat depots in 11 obese postmenopausal women: the abdominal subcutaneous and visceral depots, the pelvic subcutaneous and intrapelvic depots, and the thigh subcutaneous depot. The mean decrease in total body fat was 34 percent, with comparable decreases in total abdominal fat (33 percent) and total pelvic fat (32 percent). In the abdomen, visceral fat was reduced by 35 percent and subcutaneous fat by 33 percent. In the pelvic region, intrapelvic fat decreased by 51 percent and subcutaneous fat by 25 percent. The decrease in the size of the abdominal visceral fat depot was highly correlated with fat loss during treatment (r = 0.68). By contrast, the decrease in the size of the subcutaneous abdominal fat depot correlated less highly with fat loss. These preliminary findings suggest that obese postmenopausal women with large visceral fat depots will decrease the size of their visceral fat depots by weight reduction. This is good news since the adverse health effects of obesity are believed to be associated with visceral fat.