ABSTRACT
This study investigated the effect of habitual snacking on the diet-induced thermogenesis (DIT) in non-obese young women. Thirteen women aged 1823 yrs old were divided into two groups group one was of six women who consumed snacks; candy, cookies, chocolate, etc., “very frequently” between meals almost everyday, group two was of seven women who seldom consumed snacks. The BMI of both groups were matched (19.7±1.0kg/m<SUP>2</SUP>) . The DIT was measured 5 h after ingestion of a meal (2220 kJ=531 kcal) using the Douglas bag technique. Each subject had their DIT measured on eight occasions to obtain average DIT values because DIT had large intra-individual variability. Indeed, each subject's DIT values were markedly different (the mean intra-individual CV=39.6%) . There was no significant difference between the two groups in percentage of body fat, resting metabolic rate (RMR), or RMR/body weight. The mean value of DIT (± SD) of group one (6.4±1.2%) was lower than that of group two (7.8±0.9%) (p<0.05) . Also, the main effects of the groups and the time after ingesting the test meal on postprandial energy expenditure were significant (two-way ANOVA; p<0.001), but the interaction between the group and the time after ingesting the test meal was not significant. In conclusion, eating habits with habitual snacking blunt DIT in young women.
ABSTRACT
Underwater weighing is based on the assumption that fat-free body density is roughly constant among humans. This assumption should be examined, because fat-free body density may in fact depend on the bone mineral and water contents of the body, with fat excluded. The purpose of this study was to investigate the effects of bone mineral content (BMC) and density (BMD) on the accuracy of body fat measured underwater. The subjects were 12 young men (25.1±3.7 years, mean ± SD), some of whom were trained athletes. BMC and BMD were measured by dual-energy x-ray absorptiometry (DXA), as was body fat, as a percentage of body weight; this method is not based on the assumption that fat-free body density is the same in different individual. Body fat as a percen tage of body weight was measured underwater, also. Body fat measured by DXA was significantly correlated with that found by underwater weighing (r = 0.83, p<0.01), as expected, but the mean body fat found by DXA was 4.3% higher. The differences between results by the two methods for individuals were from -11.5% to 2.7%, and the differences were negatively correlated with BMC/fat-free weight (FFW ; r=-0.82, p < 0.01) and BMD (r=-0.85, p<0.01) . Fat-free body density ranged from 1.097 to 1.111 g/cm<SUP>3</SUP>because BMC/FFWs varied with the individual. We concluded that individual differences in BMC/FFW and BMD affected the fat-free body density. The variations in fat-free body density would give rise to systematic errors in body composition measured underwater.