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Biomedical subjects

S B Roberts

Publications and source records attributed to S B Roberts.

At least 55 records · Page 3Linked to original sources
PubMed2000

High-glycemic index foods, hunger, and obesity: is there a connection?

The relative importance of different dietary causes of obesity remains controversial. This review examines whether consumption of high-glycemic index (GI) carbohydrates may be a contributing factor. Although data from long-term studies are lacking, short-term investigations indicate that consumption of high-GI carbohydrates may increase hunger and promote overeating relative to consumption of items with a lower GI. As long-term research on GI and weight regulation accumulates, consumption of whole grain and lower GI cereals instead of highly refined cereals is a dietary change that may help prevent overeating and is consistent with current dietary guidelines.

Blood Glucose↗
PubMed2000

Energy regulation and aging: recent findings and their implications.

Old age is a time of vulnerability to unintentional weight loss, a factor that is associated with increased morbidity and premature death. Many possible causes of weight loss in old age have been suggested. The so-called anorexia of aging may play a particular role, by either reducing food intake directly or reducing food intake in response to such adverse factors as age-associated reductions in taste and smell, poor dentition, use of multiple prescription medicines, and depression. Recent studies also raise the question of whether a reduction in dietary variety may be important. These findings emphasize the need for regular monitoring of body weight to detect unintentional weight loss in older individuals and suggest testable ways to minimize the impact of the anorexia of aging on body weight through improved dietary management.

Aged↗
PubMed2000

Regulation of energy intake in older adults: recent findings and implications.

Inadequate energy intake is common in older individuals and is probably the major cause of unexplained weight loss. This summary highlights recent studies on possible causes of negative energy balance in older individuals suggesting that aging is associated with a significant impairment in the regulation of food intake that inhibits appropriate short-term and long-term compensation for normal fluctuations in energy intake. The combination of a reduced ability to regulate energy intake, decreased dietary variety, and disadvantageous social factors such as functional limitations, social isolation and depression, increases the risk of negative energy balance leading to weight loss in older individuals.

Aged↗
PubMed1999

Overeating in America: association between restaurant food consumption and body fatness in healthy adult men and women ages 19 to 80.

PURPOSE: To examine the association between the frequency of consuming restaurant food and body fatness in adults. RESEARCH METHODS AND PROCEDURES: Usual free-living dietary intake and the frequency of consuming food from seven different restaurant types (fried chicken, burger, pizza, Chinese, Mexican, fried fish, and "other") were assessed by food frequency questionnaire in 73 healthy men and women [ages 19 to 80, body mass index (BMI) 18 to 33]. In addition, body fatness (percent weight) was determined by hydrostatic weighing, and physical activity and other lifestyle parameters were assessed by questionnaire. The relationship between the frequency of consuming restaurant food and body fatness was determined after controlling for age, sex, and other confounders by using multiple regression techniques. RESULTS: Restaurant food consumption averaged 7.5+/-8.5 (Standard Deviation) times/month. After controlling for age and sex, the frequency of consuming restaurant food was positively associated with body fatness (partial r = 0.36, p = 0.003). The strength of this association did not change after controlling for education level, smoking status, and alcohol intake, but after additionally controlling for physical activity, the partial r increased to 0.42 (p = 0.004). Total daily intakes of energy, fat, and fiber were significantly associated with restaurant food consumption frequency (r = 0.59, 0.28, and -0.45, respectively, p = 0.02 to 0.0001). DISCUSSION: The frequency of consuming restaurant food was positively associated with increased body fatness in adults. The increasing proportion of household food income spent on food prepared away from home in the United States may therefore help explain the rising national prevalence of obesity.

Adipose Tissue↗
PubMed1999

Neuroticism and self-esteem as indices of the vulnerability to major depression in women.

BACKGROUND: Neuroticism and self-esteem, two commonly used personality constructs, are thought to reflect a person's underlying vulnerability to major depression. The relative strength of these predictors is not known. METHOD: Information was gathered on 2163 individual women from an epidemiological sample of female female twin pairs. Neuroticism was assessed by the Eysenck Personality Questionnaire and global self-esteem by the Rosenberg Self-Esteem Scale. Major depression (DSM-III-R criteria) and stressful life events were also assessed. The personality constructs were studied in relation to major depression by logistic regression and structural equation modelling. RESULTS: Both cross-sectionally and prospectively, examined individually, neuroticism was a stronger predictor of risk for major depression than was self-esteem. When examined together, the predictive power of neuroticism remained substantial, while that of self-esteem largely disappeared. The same pattern of findings was obtained when a subset of subjects who had recently experienced stressful life events was analysed. By trivariate twin modelling, we found that the covariation of self-esteem, neuroticism and major depression was due largely to genetic factors. When self-esteem was the 'upstream' variable, a substantial genetic correlation remained between neuroticism and major depression. By contrast, when neuroticism was the 'upstream' variable, the genetic correlation between self-esteem and major depression disappeared. CONCLUSIONS: The personality construct of neuroticism is a substantially better index of a woman's underlying vulnerability to major depression than is self-esteem. These findings suggest that overall emotionality or emotional reactivity to the environment reflects risk for depression better than does global self-concept.

Adult↗
PubMed1999

Replication of linkage studies of complex traits: an examination of variation in location estimates.

In linkage studies, independent replication of positive findings is crucial in order to distinguish between true positives and false positives. Recently, the following question has arisen in linkage studies of complex traits: at what distance do we reject the hypothesis that two location estimates in a genomic region represent the same gene? Here we attempt to address this question. Sampling distributions for location estimates were constructed by computer simulation. The conditions for simulation were chosen to reflect features of "typical" complex traits, including incomplete penetrance, phenocopies, and genetic heterogeneity. Our findings, which bear on what is considered a replication in linkage studies of complex traits, suggest that, even with relatively large numbers of multiplex families, chance variation in the location estimate is substantial. In addition, we report evidence that, for the conditions studied here, the standard error of a location estimate is a function of the magnitude of the expected LOD score.

Chromosome Mapping↗
PubMed1999

Dietary variety within food groups: association with energy intake and body fatness in men and women.

BACKGROUND: Short-term experimental studies suggest that dietary variety may influence body fatness but no long-term human studies have been reported. OBJECTIVE: The purpose of this study was to determine whether dietary variety within food groups influences energy intake and body fatness. DESIGN: Seventy-one healthy men and women (aged 20-80 y), who provided accurate reports of dietary intake and completed a body-composition assessment, were studied. RESULTS: Dietary variety was positively associated with energy intake within each of 10 food groups (r = 0.27-0.56, P < 0.05). In multiple regression analysis with age and sex controlled for, dietary variety of sweets, snacks, condiments, entrées, and carbohydrates (as a group) was positively associated with body fatness (partial r = 0.38, P = 0.001) whereas variety from vegetables was negatively associated (partial r = -0.31, P = 0.01) (R2 = 0.46, P < 0.0001). In separate models, both a variety ratio (variety of vegetables/variety of sweets, snacks, condiments, entrées, and carbohydrates) and percentage dietary fat were significant predictors of body fatness (controlled for age and sex, partial r = -0.39 and 0.31, respectively, P < 0.01). However, dietary fat was no longer significantly associated with body fatness when the variety ratio and dietary fat were included in the same model. CONCLUSIONS: Our data, coupled with those of previous short-term studies, suggest that a high variety of sweets, snacks, condiments, entrées, and carbohydrates coupled with a low variety of vegetables promotes long-term increases in energy intake and body fatness. These findings may help explain the rising prevalence of obesity.

Adipose Tissue↗
PubMed1999

Equations for predicting the energy requirements of healthy adults aged 18-81 y.

BACKGROUND: Recent studies have questioned the accuracy of using the current recommended dietary allowances (RDAs) to predict usual energy requirements in adults. OBJECTIVE: We developed equations to predict adult energy requirements from simple anthropometric and laboratory measures by using the doubly labeled water method to determine each subject's total energy expenditure (TEE), which is equal to usual energy requirements in weight-stable individuals. DESIGN: This was a cross-sectional study conducted with 93 healthy, free-living adults [44 men and 49 women; body mass index range (in kg/m2): 18.4-31.8] aged 18-81 y. Body fat and fat-free mass were measured by underwater weighing, physical activity was estimated by using activity monitors, and resting energy expenditure was determined by indirect calorimetry. Information on anthropometric variables and reported strenuous activity was also collected. RESULTS: Three regression equations were developed and verified for accuracy by using bootstrap analysis and doubly labeled water data published by other research groups. The first equation used information on only age, weight, height, and sex and had an SEE for prediction of TEE of 1.80 MJ/d. The second and third equations used different combinations of basic and laboratory data and had SEEs of 1.55 and 1.65 MJ/d, respectively. With use of the same analytic approaches, the RDAs for energy were shown to significantly underestimate usual energy needs by approximately 10%; the extent of underestimation was significantly greater for subjects with high TEEs than for subjects with low TEEs. CONCLUSION: Regression equations based on doubly labeled water measurements of TEE appear to be more accurate than the current RDAs for predicting energy requirements in healthy, nonobese adults living in affluent countries.

Adolescent↗
PubMed1999

High glycemic index foods, overeating, and obesity.

OBJECTIVE: The prevalence of obesity has increased dramatically in recent years. However, the role of dietary composition in body weight regulation remains unclear. The purpose of this work was to investigate the acute effects of dietary glycemic index (GI) on energy metabolism and voluntary food intake in obese subjects. METHODS: Twelve obese teenage boys were evaluated on three separate occasions using a crossover study protocol. During each evaluation, subjects consumed identical test meals at breakfast and lunch that had a low, medium, or high GI. The high- and medium-GI meals were designed to have similar macronutrient composition, fiber content, and palatability, and all meals for each subject had equal energy content. After breakfast, plasma and serum concentrations of metabolic fuels and hormones were measured. Ad libitum food intake was determined in the 5-hour period after lunch. RESULTS: Voluntary energy intake after the high-GI meal (5.8 megajoule [mJ]) was 53% greater than after the medium-GI meal (3.8 mJ), and 81% greater than after the low-GI meal (3.2 mJ). In addition, compared with the low-GI meal, the high-GI meal resulted in higher serum insulin levels, lower plasma glucagon levels, lower postabsorptive plasma glucose and serum fatty acids levels, and elevation in plasma epinephrine. The area under the glycemic response curve for each test meal accounted for 53% of the variance in food intake within subjects. CONCLUSIONS: The rapid absorption of glucose after consumption of high-GI meals induces a sequence of hormonal and metabolic changes that promote excessive food intake in obese subjects. Additional studies are needed to examine the relationship between dietary GI and long-term body weight regulation.

Adolescent↗
PubMed1999

The upregulation of messenger ribonucleic acids during 17alpha, 20beta-dihydroxy-4-pregnen-3-one-induced ovulation in the perch ovary.

While progestins appear to be involved in the local ovarian regulation of vertebrate ovulation, their specific role is unclear. In yellow perch (Perca flavescens) the progestin, 17alpha, 20beta-dihydroxy-4-pregnen-3-one (17,20-P), stimulates ovulation in vitro and this induction requires gene activation. Therefore, the perch model was used to isolate progestin-upregulated mRNAs. Perch ovaries were incubated for 32 h with or without 17,20-P (0.1 microg/ml). Messenger ribonucleic acids were isolated from the tissue and used for differential display PCR (DDPCR). From DDPCR, 5 bands were eventually obtained that were verified by Northern analysis to be consistently upregulated by 17,20-P at 32 h. Using these bands, full-length cDNAs were obtained by library screening and completely sequenced. Based on similarity to known sequences, four of the cDNAs presumably encode for perch forms of (1) neprilysin (PNEP-1; 63% identical); (2) a lysyl oxidase-type protein (PLO-2; 43.2% identical); (3) calmodulin (PCAL-1; 100% identical); and (4) a microtubule aggregate-like protein (PMAP-1; 29.6% identical). The fifth cDNA obtained from DDPCR most likely encodes for an egg protein and will be reported separately. Each of the cDNAs was used to probe Northern blots of ovarian mRNA taken at 0, 12, 24, 32 and 42 h of incubation with 17,20-P. This temporal Northern analysis verified that all four were upregulated by 32 h. In addition, PNEP and PMAP transcripts began to increase by 12 h, while PCAL and PLO transcripts remained elevated through 42 h. On Northern blots of RNA from other perch tissues, calmodulin was found in all tissues, PLO mRNA was ovarian specific, and PMAP mRNA was also present in the gills and liver. Multiple transcripts were observed for PNEP, but the ovarian form induced by 17,20-P was only found in high abundance in the heart. To our knowledge, this is the first report that specifically characterizes progestin upregulated mRNAs in the vertebrate ovary at ovulation.

Amino Acid Sequence↗
PubMed1998

Use of food quotients in human doubly labeled water studies: comparable results obtained with 4 widely used food intake methods.

Information on the macronutrient composition of the diet is needed in doubly labeled water studies to convert measured rates of carbon dioxide production into values for total energy expenditure. There is no general consensus, however, about the best method to determine food intake for this purpose. Four common methods of measuring food intake (7-day weighed food intake, 24-hour recall, and Fred Hutchinson Cancer Research Center/Block and Willett food frequency questionnaires) were tested for their ability to provide comparable food quotient and total energy expenditure data in doubly labeled water studies in 10 young and 10 older women. All methods gave mean values for total energy expenditure that were within 1% of each other. Individual values obtained using the 24-hour recall and food frequency questionnaires were within +/- 3% (standard deviation) of values determined using data from the 7-day weighed food record. These results suggest that it is not necessary to use time-consuming and expensive 7-day food records in doubly labeled water studies; instead, food intake data obtained more easily by 24-hour recall or food frequency questionnaire can provide comparable data.

Adult↗
PubMed1998

Effects of age on energy balance.

The effects of aging on energy requirements and energy balance have been studied by several research groups using the doubly labeled water method. The weight of evidence from these investigations suggests that current recommended dietary allowances underestimate the usual energy needs of adults of all ages, including older adults. In addition, doubly labeled water studies have found a significant negative association between body fatness and energy expenditure for physical activity, and a significant positive association between energy expenditure for physical activity and fat-free mass. Further studies are needed to refine estimates of energy requirements for different population groups and to address the role of physical activity in the prevention and treatment of obesity.

Adult↗
PubMed1998

The effects of age on postprandial thermogenesis at four graded energetic challenges: findings in young and older women.

There remains controversy over the effect of age on postprandial thermogenesis, with some studies observing decreased postprandial thermogenesis in older subjects and other studies finding no effect of age. We investigated this issue in 8 young (25.2+/-1.8 years) and 8 older (72.2+/-2.1 years) healthy glucose-tolerant women with normal thyroid hormone status. Repeated measures of the thermic effect of feeding (TEF) were obtained following consumption of test meals containing 0, 1046, 2092, and 4184 kilojoules (kJ) by using indirect calorimetry. TEF at each meal size was determined once in the older subjects and twice in the younger subjects (during follicular and luteal phases of the menstrual cycle) for a total of 96 measurements. There was a positive dose-response between meal size and TEF (p < .001) that was not significantly affected by age group. The best single predictor of TEF expressed as a percentage of meal energy content was waist-to-hip ratio (R2=67.416, p < .02). These results indicate that aging is not associated with decreased TEF in the absence of factors such as a hypothyroid state or glucose intolerance.

Adult↗
PubMed1998

Mild stunting is associated with higher susceptibility to the effects of high fat diets: studies in a shantytown population in São Paulo, Brazil.

Previous studies by our group and others have suggested that nutritional stunting may increase the risk of obesity. To investigate mechanisms that could explain a link between stunting and obesity, a 22-mo follow-up study was conducted in two groups of shantytowns school girls (7-11 y old) in São Paulo, Brazil. One group (n = 15) had mild stunting (defined using a cutoff of -1.4 Z-scores of height-for-age) but normal weight-for-height; the control group (n = 15) had normal weight and height. Similar energy intake, dietary macronutrient composition and energy expenditure were observed in the two groups. Both groups showed comparable levels of IGF-1 that were below the normal range. A significant and positive association between baseline IGF-1 and the change in height-for-age during follow-up was found in all subjects combined (P = 0.044). A significant association was found between the baseline percentage of dietary energy supplied by fat and the gain in weight-for-height during follow-up in girls with mild stunting (P = 0.048), but not in the nonstunted control girls (P = 0.245); however, the slopes of these relationships were not significantly different. This study raises the question of whether a diet high in fat may increase the susceptibility to excess body fat gain in children who are mildly stunted. Further studies are need to explore this issue and to examine the possible etiological role of low levels of IGF-1.

Brazil↗
PubMed1998

Confirmation of the diagnosis of schizophrenia after death using DSM-IV: a Victorian experience.

OBJECTIVE: This study examines the reliability of antemortem diagnoses of schizophrenia using DSM-IV criteria. METHOD: The case histories of 83 subjects with a provisional diagnosis of schizophrenia at autopsy were retrospectively reviewed using a semi-structured chart review and application of DSM-IV criteria. Agreement between antemortem and postmortem diagnoses of schizophrenia was examined, as well as the concordance between DSM-IV diagnoses and previously obtained diagnoses using DSM-III-R and ICD-10 criteria for schizophrenia. RESULTS: According to DSM-IV, 30.1% of cases did not have schizophrenia, compared to 36.1% using DSM-III-R criteria and 51.8% of cases using ICD-10 criteria. Concordance between DSM-IV and DSM-III-R diagnoses of schizophrenia was excellent (kappa = 0.81), but only fair between DSM-IV and ICD-10 (kappa = 0.57). Of the cases that did not meet the formal criteria for schizophrenia, the majority were reassigned diagnoses of schizoaffective disorder and affective disorder. CONCLUSIONS: The use of human brain tissue in postmortem studies of schizophrenia must be linked to standardised diagnostic assessment procedures. Diagnoses can be upgraded with the development of new criteria, providing sufficient clinical data is available in case histories.

Adult↗