The UCLA population studies of chronic obstructive respiratory disease. 5. Agreement and disagreement of tests in identifying abnormal lung function.

The relative sensitivity and specificity of symptoms, spirometry, the flow-volume (FV) curve, the single-breath nitrogen test (SBNT), and specific airway conductance (SGaw) were estimated by cross comparison of these tests with the FEV1/FVC ratio and other tests in 1,201 residents of Los Angeles. Spirometry and the flow-volume curve were estimated to be the most sensitive, yet reasonably specific composite measures, and FEV1/FVC and V75 to be the most sensitive individual indices. Among current smokers, FEV1/FVC was more frequently abnormal (23 percent) than FEF25-75% (16 percent), showed higher concordance with an abnormal FEF25-75% (88 percent), and identified a greater percentage of individuals as abnormal when the FEF25-75% was normal (9 percent) than vice versa. SGaw and SBNT showed a poor concordance with FEV1/FVC and identified more individuals as abnormal who had a normal FEV1/FVC. Although the proportion of current smokers with productive cough was relatively high (26 percent), none of the function tests showed a reasonable concordance with this symptom. These findings suggest that: 1) spirometry, the flow-volume curve, V75 and FEV1/FVC are relatively sensitive and specific indicators of respiratory impairment; 2) spirometry and the FV curve provide similar but not completely overlapping information; 3) SGaw and SBNT yield different (or less specific) information than the other tests; and 4) effects of cigarette smoking identified by productive cough are different from those identified by other tests.

Lower fat intake as a predictor of initial and sustained weight loss in obese subjects consuming an otherwise ad libitum diet.

OBJECTIVE: To determine what predicts initial and sustained weight loss in subjects consuming a reduced-fat diet ad libitum and the relationship between achieved level of fat intake and weight loss. DESIGN: Placebo arm of a randomized, controlled trial of a weight-loss drug (dexfenfluramine) in the context of an ad libitum, reduced-fat diet. SUBJECTS: Thirty-nine subjects (initial mean body mass index +/- standard deviation = 34.9 +/- 3.4; body mass index is calculated as kg/m2) from the placebo group who completed the 9-month study. INTERVENTION: Dietary assessment and education (month 0) followed by monthly meetings during the single intervention of reducing fat intake (months 1 through 6); one follow-up at 9 months. MAIN OUTCOME MEASURES: Initial weight loss (first 3 months) and sustained weight loss (over 9-month period). STATISTICS: Dietary intake, body size, exercise levels, age, and gender were included in multiple regression linear models of initial and sustained weight loss if they were significant independent predictors. RESULTS: Greater initial weight loss was associated with a greater decrease in fat intake and a lower achieved fat intake at 3 months. Greater sustained weight loss was associated with a lower achieved fat intake, a higher baseline waist circumference, and higher moderate-intensity exercise levels (months 3 and 6). Weight loss occurred in all subjects who reported a fat intake of 40 g/day or less. APPLICATIONS: The obese persons most likely to achieve and sustain weight loss on an ad libitum, reduced-fat diet are those who can substantially reduce fat intake, those with high initial levels of abdominal fat, and those who undertake regular moderate-intensity exercise. A target of less than 40 g fat per day might be an appropriate goal to ensure weight loss, but dietary underreporting and the difficulty of sustaining very-low-fat intakes need to be considered.

Dexfenfluramine as an adjunct to a reduced-fat, ad libitum diet: effects on body composition, nutrient intake and cardiovascular risk factors.

OBJECTIVE: To investigate the specific effects of dexfenfluramine (dF) as an adjunct to a reduced-fat, ad libitum diet. DESIGN: Double-blind, randomized, placebo-controlled study. Subjects were stabilized on the dietary program during a 12 w run-in period, and then were randomized to receive dF (15 mg) or placebo bd for an additional 12 w. One follow-up was conducted 12 w after cessation of treatment. SUBJECTS: 84 obese subjects (57 F; 27 M, mean body mass index = 34.7 +/- 3.2 kg/m2). MEASUREMENTS: Body composition (by DEXA), fat distribution (by circumferences and DEXA), nutrient intake (by 7 d food diaries), blood lipids, blood glucose and blood pressure. RESULTS: Mild side effects were reported by 19 dF subjects, and in seven subjects lethargy or dry mouth persisted for the 12 w of treatment. Relative to placebo, treatment with dF was associated with significantly greater reductions in body weight (-3.8 kg, 95% confidence interval [CI] = -4.9, -2.7), fat mass (-2.5 kg, 95% CI = -3.6, -1.4) and fat-free mass (-1.2 kg, 95% CI = 1.8, -0.7). Waist and hip circumferences also decreased (P < 0.01) but the waist:hip ratio remained unchanged. The ratio of waist:hip fat mass as measured by DEXA decreased more in the dF group (P < 0.01). Lower total energy intake (-439 kJ/d, 95% CI = -932, 54) and fat intake (-5.1 g/d, 95% CI = -10.8, 0.6) were also seen but were of borderline statistical significance. After adjusting for changes in fat intake, dF treatment was associated with lower cholesterol and triglyceride concentrations (P < 0.01). Twelve weeks following cessation of treatment, the rate of weight gain was not significantly different between the dF and the placebo groups (1.7 kg and 0.7 kg respectively), but the dF group remained significantly lighter than the placebo group (P < 0.01). CONCLUSIONS: Dexfenfluramine treatment augments weight and fat loss on a reduced-fat, ad libitum diet, with some evidence for preferential loss of waist fat compared with hip fat. The decreases in total energy and fat intake with dF seem insufficient to explain the significant decreases in body weight and fat mass.

Body size and composition in Polynesians.

OBJECTIVES: To compare the relationship between body size and body composition in New Zealanders of Polynesian and European descent and to develop specific regression equations for fat mass for Polynesians. SUBJECTS: 189 Maori (93 males, 96 females), 185 Samoans (88 males, 97 females) and 241 Europeans (89 males, 152 females) aged 20-70 y. MEASUREMENTS: Height, weight, four skinfold thicknesses, bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA). RESULTS: At higher body mass index levels, Polynesians (Maori and Samoans combined) had a significantly higher ratio of lean mass:fat mass compared with Europeans. Four multiple regression equations incorporating resistance and reactance, height and weight, sum of four skinfolds or sum of two skinfolds were developed in two-thirds of the Polynesian participants using DXA fat mass as the dependent variable. In the remaining one-third of participants, the mean difference between fat mass predicted by these equations (r2 range 0.89-0.93) and DXA fat mass ranged from -0. 06 to +0.25 kg (s.d. -3.67 to +3.71 kg). CONCLUSION: At higher BMI levels, Polynesians were significantly leaner than Europeans, implying the need for separate BMI definitions of overweight and obesity for Polynesians. The regression equations using BIA, height and weight or skinfold thicknesses were good predictors of body composition in Polynesians.