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Biomedical subjects

S B Roberts

Publications and source records attributed to S B Roberts.

At least 73 records · Page 4Linked to original sources
PubMed1997

Relationship between circulating leptin and energy expenditure in adult men and women aged 18 years to 81 years.

Recent studies suggest that leptin may be an important metabolic signal for energy regulation in rodents, but the role of leptin in human energy regulation remains uncertain. Because adaptive variations in energy expenditure play an important role in human energy regulation, we investigated the relationship between leptin and energy expenditure parameters in 61 weight-stable men and women aged 18 years to 81 years who were not obese. Measurements were made of circulating leptin in the fasting state, body fat and fat free mass, resting metabolic rate (n = 61), free-living total energy expenditure (n = 52), and the thermic effect of feeding (n = 33). After statistically accounting for age, body fat, and fat free mass, there was no association between leptin and any measured energy expenditure parameter. In addition, there was no effect of age on the relationship between circulating leptin and body fat mass. These results indicate that physiological variations in circulating leptin are not linked with adaptive variations in energy expenditure in humans, in contrast to indications of this phenomenon in the ob/ob mouse.

Adipose Tissue↗
PubMed1997

Soluble fiber and energy regulation. Current knowledge and future directions.

Soluble dietary fiber is a potentially important factor determining our ability to maintain a stable energy balance and avoid obesity. However, clinical metabolic investigations have given conflicting results on the effects of soluble fiber on energy regulation, perhaps for the reasons that a) other dietary components that affect energy regulation have not always be controlled adequately and b) in the past it has been hard to ensure that subjects are consistently compliant with the dietary requirements of soluble fiber protocols. The recent development of techniques for assessing dietary compliance in metabolic studies, combined with increased control of non-fiber dietary variables that influence energy intake, should help ensure more consistent findings in future investigations.

Adolescent↗
PubMed1997

Fat oxidation in response to four graded energy challenges in younger and older women.

We examined whether older individuals have an impairment in their ability to oxidize dietary fat, a factor that could help to explain age-associated weight gain. The subjects were 16 healthy younger and older women. Fat oxidation was determined by indirect calorimetry before and after consumption of four different test meals consumed > or = 5 d apart. The intervention meals contained 0, 1046, 2092, or 4184 kJ (simulating extended fasting, and consumption of a snack, a small meal, and a moderately large meal, respectively), with 35% of energy from fat. The duration of each measurement was the amount of time required for postprandial energy expenditure to return to the premeal fasting value. A total of 96 measurements were obtained, including duplicates for all meal sizes in the younger women (in the follicular and luteal phases of the menstrual cycle). Total postprandial fat oxidation increased in proportion to meal size in the younger subjects, but did not increase above that for the 2092-kJ meal in the older women. In addition, older subjects had significantly lower total fat oxidation after consumption of the 4184-kJ meal (781 compared with 1029 kJ/measurement, P < 0.02) and also significantly greater fat deposition (745 compared with 464 kJ/measurement, P < 0.02). These findings suggest that, relative to younger women, older women have a reduced ability to oxidize dietary fat when they consume large meals.

Adult↗
PubMed1997

Effect of high-fat and low-fat diets on voluntary energy intake and substrate oxidation: studies in identical twins consuming diets matched for energy density, fiber, and palatability.

There remains controversy over the effects of dietary fat content on voluntary energy intake. Additionally, the question of whether there is a genetic susceptibility to overeating high-fat diets has not been resolved. To address these issues, we designed two diets: a low-fat diet providing approximately 20% of energy as fat and a high-fat diet with approximately 40% of energy as fat. The diets were matched for energy density, fiber, and palatability. In a two-phase, 18-d intervention study, voluntary energy intakes and macronutrient oxidation rates during the fasting and fed states were determined in seven pairs of identical male twins. In contrast with results of previous intervention studies, in which low-fat and high-fat diets were not matched for energy density and other associated variables, we observed no significant difference in voluntary energy intake between the low-fat and high-fat phases, and mean daily intakes were similar (10.3 and 10.7 MJ/d, respectively). Postprandial rates of fat oxidation tended to reflect fat intakes in the two dietary phases, thus helping to explain the lack of a difference in mean energy intakes. There was also a significant twin-pair similarity in differences in energy intakes between dietary phases (P = 0.013). These results suggest that dietary fat content does not have a major influence on voluntary energy intake when dietary variables usually associated with fat are controlled for and that there may be a familial influence on the effects of dietary fat content on energy intake.

Adult↗
PubMed1996

Effects of energy imbalance on energy expenditure and respiratory quotient in young and older men: a summary of data from two metabolic studies.

The roles of energy expenditure and substrate oxidation in energy regulation, and the effects of factors such as aging on these parameters, remain uncertain. A re-analysis of data from two studies involving overfeeding or underfeeding in young men (22.7 +/- 0.6 [SEM] years) and older men (68.0 +/- 1.50 years) was conducted to further evaluate the adaptive capacity of energy expenditure and respiratory quotient to an increase or a decrease in energy intake. Changes in total energy expenditure (TEE) and resting energy expenditure (REE) and respiratory quotient (RQ) in response to energy imbalance were compared between subjects undergoing overfeeding by 4.1 MJ/day for 21 days, or underfeeding by 3.2 MJ/day for 21 days. Comparing responses to overfeeding or underfeeding, there was a significant TEE response to energy imbalance averaging 1.39 MJ/day and equivalent to 19% of the alteration in energy intake (p < 0.05). There was also a significant REE response to energy imbalance averaging 0.45 MJ/day (p < 0.001), and a significant RQ response in both fasting and fed states (p < 0.01). There was no significant difference between young and older men in their TEE, energy deposition or RQ responses to energy imbalance, but older men did have significantly diminished REE response to energy imbalance (p < 0.05) and a significantly delayed thermic response to a standard meal (p < 0.05). These data indicate that energy expenditure plays a significant role in attenuating the effects of alterations in energy intake on body energy stores and that, based on some measures of energy expenditure, aging is associated with a reduction in the adaptive capacity of energy expenditure to participate in energy regulation.

Adult↗
PubMed1996

Evaluation of four methods for determining energy intake in young and older women: comparison with doubly labeled water measurements of total energy expenditure.

The accuracy and precision of four different food intake assessment methods were evaluated in young and older women by comparing reported energy intakes with doubly labeled water measurements total energy expenditure (TEE). A study lasting 8 d was conducted in 10 young women aged 25.2+/-1.1 y (-x+/-SEM) and in 10 older women aged 74.0+/-1.4 y. Free-living TEE was measured over 7 d and food consumption was determined from weighed food intake data (7 d), a 24-h food recall (in duplicate), and two different food-frequency questionnaires [Fred Hutchinson Cancer Research Center (FHCRC)/Block and Willett, both in duplicate]. In addition, body composition was determined by using hydrodensitometry, and strenuous physical activity and the extent of dietary restraint were determined by questionnaire. In young women, 24-h recall gave mean energy intakes that were closest to measures of TEE (-0.34+/-3.71 MJ/d compared with TEE, P=0.178), and energy intakes by food-frequency questionnaires were the only intake data that correlated significantly with individual values for TEE (P<0.05). In older women, food-frequency questionnaires gave mean energy intakes that were closest to measured TEE (+0.53+/-2.95 MJ/d with the Willett questionnaire and -1.19+/-3.02 MJ/d with FHCRC/Block questionnaire). No energy intake data from this group correlated significantly with values for TEE. The 7-d weighed dietary intakes were significantly lower than measured TEE in both young and older women (-2.0 MJ/d in young and older women combined, P<0.001), and did not correlate significantly with values for TEE, although they did most closely mirror the mean difference in TEE between the young and older women (2.30 MJ/d for TEE and 2.11 MJ/d for 7-d weighed intake). These data suggest that none of the methods studied gave accurate estimates of the usual energy requirements of individual subjects. In addition, the results suggest that for some types of studies, simple methods for assessing group mean dietary intake may actually give more accurate information than weighed dietary intakes.

Adult↗
PubMed1996

Effects of age on energy expenditure and substrate oxidation during experimental overfeeding in healthy men.

Relatively little is known about the influence of age on energy regulation during energy imbalance. We compared the effects of overfeeding on changes in energy expenditure, substrate oxidation, and energy deposition between young men (age 23.7 +/- 1.1 [SEM] years) and older men (age 70.0 +/- 7.0) of normal body weight who were leading unrestricted lives. Changes in total energy expenditure, resting energy expenditure (REE), the thermic effect of feeding (TEF), respiratory quotient (RQ), and body energy content were determined in response to overeating by 4.09 +/- 0.07 Megajoule (MJ)/day for 21 days in 16 healthy subjects consuming a typical diet. After excluding data from one young subject with unusual results and adjusting for individual differences in excess energy intake, there was a tendency towards a smaller increase in REE in older men compared to the young men (p = .07) which was accounted for by their lower fat-free mass (p = .016). There was also a significantly smaller increase in resting energy expenditure averaged over fasting and fed states (i.e, REE + TEF) with overfeeding in older men than in young men (p < .01). Combined, these smaller increases in energy expenditure with overfeeding in the older subjects averaged an estimated 365 kilojoule (kJ)/day (8.9% of the excess energy intake) (p < .02). There were also significant effects of age on fasting RQ (p < .001) and the change in RQ with overfeeding (p < .001), but no significant increase in energy expenditure for physical activity and thermoregulation with overfeeding in either age-group. These results are consistent with the suggestion that older individuals experience both a reduction in the ability to increase energy expenditure, and an alteration in the pattern of substrate utilization, in response to overfeeding. These changes may promote cumulative increases in body energy during normal cycles of positive energy balance unless compensated for by adaptive variations in energy intake.

Adult↗
PubMed1996

Effects of age on energy expenditure and substrate oxidation during experimental underfeeding in healthy men.

Relatively little is known about the influence of age on energy regulation during energy imbalance. We compared the effects of underfeeding on changes in energy expenditure, substrate oxidation, and body energy loss between young men (age 22.0 +/- 0.9 [SEM] years) and older men (age 66.0 +/- 1.8) who were leading unrestricted lives. Changes in total energy expenditure (TEE), resting energy expenditure (REE), the thermic effect of feeding (TEF), respiratory quotient, and body energy loss were determined in response to undereating by 3.17 +/- 0.16 Megajoule (MJ)/day for 21 days in 19 healthy subjects consuming a typical diet. No significant effects of age were observed in changes in TEE, REE, TEF, or body energy loss in response to underfeeding. Thus, older men do not appear to have any impairment of energy conservation during negative energy balance compared to young men. This normal pattern of energy conservation during undereating together with the previously demonstrated reduction in energy dissipation during overeating can be predicted to promote body fat deposition in older men during the cycles of positive and negative energy balance that occur during normal life. This finding may help to explain the increased body fat mass in older individuals.

Adult↗
PubMed1996

Postabsorptive and postprandial energy expenditure and substrate oxidation do not change during the menstrual cycle in young women.

There is little information on the effects of the menstrual cycle on the thermic effect of feeding (TEF) and postprandial substrate oxidation. To address these issues, a dose-response study was conducted in eight young women to whom test meals containing 0, 1046, 2092 and 4148 kJ were administered on nonconsecutive days, once each during the follicular phase and once during the luteal phase of the menstrual cycle. Postprandial energy expenditure was measured until it returned to base line (test duration for the 0 kJ meal was matched to duration of 4184 kJ meal). There was no significant difference between menstrual cycle phases in the duration of the thermogenic response to any size meal. TEF, calculated by four different methods, did not differ between follicular and luteal phases, and a comparable dose-response was observed in both phases. Similarly, there was no effect of menstrual cycle phase on postabsorptive or postprandial protein, fat, or carbohydrate oxidation. In conclusion, postabsorptive and postprandial energy expenditure and substrate oxidations did not differ in young women during the follicular and luteal phases of the menstrual cycle.

Adult↗
PubMed1996

The new obesity genes.

Individual susceptibility to obesity is recognized to be influenced significantly by genetic inheritance. Recently, candidate obesity genes have been identified that may contribute to the inheritance of body fat mass and the partitioning of fat between central and peripheral fat depots. In studies of animal models of obesity, the genetic basis for obesity in the obese (Ob/Ob) mouse, the Fat mouse, and the Yellow (Vvy) mouse has been identified. Further research is needed to determine whether abnormalities in these genes contribute to human obesity as well. In studies of humans, sequence variation in at least six genes has been linked to increased body fatness and/or susceptibility to obesity. In addition, five other encoding genes have been linked to a disproportionate storage of fat in the abdominal region. These genes identified in studies of humans are currently thought to be modifying or background genes, each separately conferring a modest increase in susceptibility to fatness. Further research is needed to identify additional candidate genes that confer susceptibility to obesity and to determine the relative importance of each one in a range of human populations with distinct environments.

Adipose Tissue↗
PubMed1995

Multiple laboratory comparison of the doubly labeled water technique.

A double-blind study was conducted to determine between-laboratory variability in the doubly labeled water method for measurement of total energy expenditure in humans, and to compare the accuracy and precision of three widely-used procedures for calculating rates of carbon dioxide production from the original isotope data. Eighteen laboratories from five countries participated in the study. All laboratories were provided with five water standards containing varying amounts of 2H and 18O, and in addition 11 laboratories were provided with urine and dose specimens from one (six laboratories) or two (five laboratories) healthy elderly subjects of normal height and weight undergoing a calorimetric validation of the doubly labeled water method. The data from the five water standards were analyzed to predict between-laboratory variability in the doubly labeled water technique in all laboratories. In addition, data from the subjects were analyzed using the "slope-intercept", "2-point" and "modified" methods of calculation. The results confirm that the doubly labeled water method can be an accurate technique for the measurement of energy expenditure in adult human subjects in some laboratories. However, there was substantial between-laboratory variability in the results and some laboratories returned physiologically impossible results. There was no significant effect of calculation procedure on the accuracy of the technique in this limited comparison, although the slope-intercept procedure appeared to be more susceptible to analytical error than the other procedures. The isotope standards analyzed by participants in this study will be made available to other investigators on request.

Aged↗
PubMed1995

Obesity and malnutrition in a Shantytown population in the city of São Paulo, Brazil.

To investigate the prevalence of obesity and malnutrition in the poor Brazilian population we conducted a survey on the socioeconomic and nutritional status of 535 families (comprising 2,411 individuals) living in shantytowns in the city of São Paulo. There was a 30% prevalence of malnutrition in the children, with chronic malnutrition as the most predominant problem. The prevalence of obesity was 6.4% in boys and 8.7% in girls. Overweight and obesity associated with stunting was found in 5.8% of boys and 6.8% girls. Adolescents showed a higher prevalence of malnutrition when weight-for-age distribution was used (boys 46.4%, girls 40.2%), but a right deviation in the distribution was observed with an increase in obesity and a decrease of malnutrition was observed (obesity was 21% in girls and 8.8% in boys; malnutrition was 15.5% in boys and 12.6% in girls) when the weight-for-height adjustment was made. Stunting was the most predominant type of malnutrition in both sexes. Obesity associated with stunting was more common than obesity without stunting, both in younger children and adolescents. Adults had a higher prevalence of obesity than malnutrition according to both the Metropolitan Life Insurance tables (1.7% of undernutrition, 16.7% of overweight, and 14.1% of obesity) and Body Mass Index (8.5% of undernutrition, 21.9% of overweight, and 14.6% of obesity). There was an increase in the percentage of obese children when at least one adult in the family was obese and an increased percentage of malnourished children when undernourished adults were present in the family. Obesity among the adults of the family decreased the occurrence of malnutrition among the children.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Abnormalities of energy expenditure and the development of obesity.

The role of energy expenditure in the development of obesity remains unclear. This issue is examined using data from prospective studies of energy expenditure and obesity, the effects of overfeeding and diet composition on energy expenditure, and studies of the relationship between energy expenditure for physical activity and body composition. The combined results from these investigations strongly support the view that low energy expenditure can facilitate rapid weight gain in susceptible individuals. It is speculated that, in susceptible individuals, low energy expenditure for resting energy expenditure as well as physical activity are part of a range of mechanisms available for providing surplus energy for rapid weight gain. In addition, both cross-sectional and intervention studies indicate that there is an equilibration between the level of energy expenditure for physical activity and body fat content. While genetic and other factors clearly play an important role in this relationship, it appears that a modest reduction in body fat content can be achieved by increasing energy expenditure for physical activity in physical exercise programs.

Adolescent↗
PubMed1995

Dietary energy requirements of young and older women determined by using the doubly labeled water method.

There is little information on the effects of age on energy requirements in women. This issue was investigated in a cross-sectional study of 10 normal-weight young women aged 25.2 +/- 1.1 y (mean +/- SEM) and 10 normal-weight older women aged 74.0 +/- 1.4 y. In a 9-d study, measurements were made of free-living total energy expenditure (TEE) by using the doubly labeled water technique, body composition by using hydrodensitometry, and resting energy expenditure (REE) by using indirect calorimetry. Mean values for reported levels of strenuous activity were within the expected range in both groups (31 +/- 13 min/d in the young group and 7 +/- 2 min/d in the older group). Energy requirements expressed as the ratio of TEE to REE were 1.80 +/- 0.10 and 1.62 +/- 0.06 (P < 0.01) in the young and older group, respectively. When values for REE predicted from body weight (pREE) were used, as suggested in the current recommended dietary allowances (RDAs), the ratios of TEE to pREE in the two groups were 1.85 +/- 0.10 and 1.54 +/- 0.04 (P < 0.05). The RDAs significantly under-predicted the energy requirements of the young group (P < 0.05), but there was no significant underprediction in the older group. Although obtained in a relatively small number of subjects, these results provide no evidence to indicate that the current RDAs underestimate the energy requirements of older women, in contrast with previous observations of an underestimation of energy requirements by the RDAs in older men.

Adult↗