PubMed HealthSearch

Biomedical subjects

J O Hill

Publications and source records attributed to J O Hill.

At least 19 recordsLinked to original sources

A descriptive study of individuals successful at long-term maintenance of substantial weight loss.

The National Weight Control Registry (NWCR) is, to the best of our knowledge, the largest study of individuals successful at long-term maintenance of weight loss. Despite extensive histories of overweight, the 629 women and 155 men in the registry lost an average of 30 kg and maintained a required minimum weight loss of 13.6 kg for 5 y. A little over one-half of the sample lost weight through formal programs; the remainder lost weight on their own. Both groups reported having used both diet and exercise to lose weight and nearly 77% of the sample reported that a triggering event had preceded their successful weight loss. Mean (+/-SD) current consumption reported by registry members was 5778 +/- 2200 kJ/d, with 24 +/- 9% of energy from fat, Members also appear to be highly active: they reported expending approximately 11830 kJ/wk through physical activity. Surprisingly, 42% of the sample reported that maintaining their weight loss was less difficult than losing weight. Nearly all registry members indicated that weight loss led to improvements in their level of energy, physical mobility, general mood, self-confidence, and physical health. In summary, the NWCR identified a large sample of individuals who were highly successful at maintaining weight loss. Future prospective studies will determine variables that predict continued maintenance of weight loss.

Adult

Contribution of energy intake and tissue enzymatic profile to body weight gain in high-fat-fed rats.

The purpose of the current study was to examine the enzymatic profile [phosphofructokinase (PFK), beta-hydroxyacyl-CoA dehydrogenase (HADH), and citrate synthase (CS)] in gastrocnemius muscle, heart, and liver in rats allowed ad libitum access to a high-fat diet (HFD, 45% of kcal from corn oil). Male Wistar rats were fed a low-fat diet (LFD, 12% of kcal from corn oil) for a 2-wk baseline period after which some continued on the LFD and others were placed on the HFD. After 1 wk on the HFD, rats were categorized as obesity-resistant (OR), -intermediate (OI), or -prone (OP) on the basis of body weight gain (OR, lower tertile; OI, middle tertile; OP, upper tertile). At 1, 2, and 5 wk, rats from each group were killed (n = 9-14 from each group/time point) after a 24-h fast. At the end of the 5-wk dietary period, weight gain was 114.8 +/- 4.3 in LFD, 125.2 +/- 3.7 in OR, 147.1 +/- 4.1 in OI, and 173.7 +/- 3.5 g in OP rats (OP > OI > OR, LFD; P < 0.001). Energy intake was highly correlated with weight gain on the HFD at each time point (r > or = 0.72, P < 0.001). After 1 wk on the HFD, significant correlations between the ratio of PFK/HADH (an indication of the relative capacity for glycolysis vs. beta-oxidation, r = 0.4, P = 0.03) and HADH/CS (an indication of the capacity for beta-oxidation relative to total oxidative capacity, r = -0.56, P = 0.001) in the gastrocnemius muscle and weight gain were observed. At week 2, significant correlations between these ratios and weight gain were observed in the gastrocnemius, liver, and heart. In contrast, these ratios were not significantly correlated with weight gain at 5 wk. These results suggest that rats most susceptible to weight gain or a HFD are characterized by a continuous increase in energy intake (explaining approximately 50% of the variance in weight gain) and an early tissue enzymatic profile that favors carbohydrate over fat use.

3-Hydroxyacyl CoA Dehydrogenases

Reduced insulin suppression of glucose appearance is related to susceptibility to dietary obesity in rats.

To examine the relationship between insulin action and body weight regulation in male rats, the following studies were performed. In study 1, rats (n = 31) were fed a low-fat diet (LFD) for 4 wk, and then glucose kinetics were estimated under basal and hyperinsulinemic conditions using the glucose clamp. After clamps, these same rats were placed on a high-fat diet (HFD) for 5 wk. In study 2, rats (n = 30) were fed an LFD for 3 wk and then a high-sucrose diet for 1 wk to produce selective hepatic insulin resistance. Clamps were then performed, and after clamps, these same rats were placed on an HFD for 5 wk. In study 3, rats (n = 30) were fed an LFD for 1 wk and then a high-sucrose diet for 3 wk to produce widespread insulin resistance. Clamps were then performed, and after clamps, these same rats were placed on an HFD for 5 wk. The rate of glucose appearance (R(a)) during the hyperinsulinemic clamps was the only pre-HFD variable that correlated (r = 0.49, P < 0.01 in study 1; r = 0.51, P < 0.001 in study 2) with weight gain on the HFD. Clamp R(a) also correlated with energy intake on the HFD in study 1 (r = 0.64, P < 0.001) and study 2 (r = 0.59, P < 0.001). Clamp R(a) and energy intake on the HFD accounted for similar portions of the variance in body weight gain on the HFD. Weight gain and fat-pad mass were increased (P < 0.05) in study 2 compared with study 1. In study 3, pre-HFD glucose kinetics were not correlated with energy intake or weight gain on the HFD. Widespread insulin resistance did not significantly reduce the rate of weight gain on the HFD. Thus insulin action on R(a) can influence body weight gain on an HFD. The effects of R(a) on body weight gain appear to be mediated via effects on energy intake. Selective hepatic insulin resistance can increase body weight gain on an HFD, but widespread insulin resistance does not significantly reduce HFD-induced weight gain.

Analysis of Variance

Nutrition and physical activity program to attenuate obesity and promote physical and metabolic fitness in elementary school children.

Obesity and low levels of physical and metabolic fitness are risk factors for cardiovascular disease and diabetes. The purpose of this investigation was to attenuate obesity and improve physical and metabolic fitness in elementary school children. Schools have the opportunity, mechanisms, and personnel in place to deliver nutrition education, fitness activities, and a school food service that is nutritious and healthy. Cohorts from grades 3 to 5 in two school districts in rural Nebraska (Intervention/Control) participated in a 2-year study of physical activity and modified school lunch program. Data collection for aerobic capacity, body composition, blood chemistry, nutrition knowledge, energy intake, and physical activity was at the beginning and end of each year. Int received enhanced physical activity, grade specific nutrition education, and a lower fat and sodium school lunch program. Con continued with a regular school lunch and team sports activity program. At year 2, Int lunches had significantly less energy (9%), fat (25%), sodium (21%), and more fiber (17%). However, measures of 24-hour energy intake for Int and Con showed significant differences for sodium only. Physical activity in the classroom was 6% greater for Int compared to Con (p < 0.05) but physical activity outside of school was approximately 16% less for Int compared to Con (p < 0.05). Body weight and body fat were not different between schools for normal weight or obese children. No differences were found for cholesterol, insulin, and glucose; however, HDL cholesterol was significantly greater and cholesterol/HDL was significantly less for Int compared to Con (p < 0.05). It appears that compensation in both energy intake and physical activity outside of school may be responsible for the lack of differences between Int and Con.

Blood Glucose

Energy and macronutrient consumption of elementary school children served modified lower fat and sodium lunches or standard higher fat and sodium lunches.

OBJECTIVE: To determine the energy and macronutrient consumption of elementary school children served modified lower fat and sodium or typical higher fat and sodium school lunches. DESIGN: The intervention school received lunches with < 30% of energy from fat and < 1000 mg sodium. The control school received typical lunches with 35% of energy from fat and > 1000 mg sodium. Served lunches were analyzed from menus and consumed lunches were analyzed using USDA plate waste methodology. SUBJECTS: Eighty intervention and 80 control subjects matched for ethnicity and economic status. RESULTS: Intervention school menus were significantly lower for energy, sodium, and fat compared to the control school. From analysis of plate waste, children from both schools consumed approximately 25% less energy than served (p < 0.05). Consumption of fat as a percentage of total energy and consumption of sodium was significantly less for the intervention compared to the control school. Compensation for the lower fat meals by the intervention school children (eating greater portions of high fat items) was not evident as the percentage of energy from fat consumed was only 1.3% greater than the percentage which was served. CONCLUSIONS: Lunch meals in this study were consumed as served. Intervention school children served lower fat and sodium meals consumed less fat and sodium than control school children and did not selectively eat only higher fat and sodium items.

Child

Measuring the thermic effect of food.

The thermic effect of food (TEF), defined as the increase in metabolic rate after ingestion of a meal, has been studied extensively, but its role in body weight regulation is controversial. We analyzed 131 TEF tests from a wide range of subjects ingesting meals of varying sizes and compositions. Each test lasted 6 h. Of the total 6-h TEF, 60% of the total had been measured after 3 h. 78% after 4 h, and 91% after 5 h. We developed a three-parameter curve to fit the data, which reduced noise and gave additional information about the TEF. The area under this parametric curve was positively correlated with fat-free mass (FFM) and meal size (MS) and negatively correlated with meal size squared (MS2) with an R2 of 0.35. The usual area under a curve created by connecting the data points of a line was correlated with the same factors but with an R2 of 0.28. The peak of the parametric curve was positively correlated with FFM and MS and negatively correlated with MS2, percent body fat, and meal composition. The time at which the peak occurred correlated positively with MS and percent fat in the meal. Our analysis suggests that an inadequate measurement duration of the TEF could lead to errors. In general, we recommend that the TEF be measured for > or = 5 h.

Adolescent

Physical activity, fat balance, and energy balance.

In this paper, we review the impact of physical activity on energy and macronutrient balances. Stability of body weight and body composition depends on reaching a steady-state where the amount and composition of energy ingested are equal to the amount and composition of energy expended. We describe how a person's level of physical activity can have a significant impact on determining the level of body weight and body fatness at which that steady-state is reached. First, physical activity can directly affect both total energy intake and total energy expenditure. Physical activity can also affect fat balance, and it is becoming clear that imbalances in total energy are largely imbalances in fat. High levels of physical activity should help individuals reach fat and energy balances at lower levels of body fatness than would have been achieved at lower levels of physical activity.

Adipose Tissue

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

Tissue oxidative capacity, fuel stores and skeletal muscle fatty acid composition in obesity-prone and obesity-resistant rats.

The purpose of the present study was to compare tissue oxidative capacity, skeletal muscle fatty acid composition, and tissue fuel stores in low-fat fed (LFD, 12% of energy from corn oil) male Wistar rats, and in high-fat fed (45% of energy from corn oil) obesity-prone (OP) and obesity-resistant (OR) male Wistar rats. Designation of OP and OR rats was based on body weight gain (upper tertile for OP; lower tertile for OR) after 5 weeks on the high-fat diet. Body weight gain over the 5-week dietary period was 91 +/- 9 g in LFD, 98 +/- 4 g in OR, and 158 +/- 5 g in OP (p < 0.05 vs. LFD and OR). Energy intake over the 5-week dietary period was 3099 +/- 101 kcal in LFD, 3185 +/- 51 kcal in OR, and 3728 +/- 45 kcal in OP (p < 0.05 vs. LFD and OR). Maximal citrate synthase activity (mumol.g-1.min-1) in the gastrocnemius muscle was not significantly different among groups: 12.1 +/- 2.4 in LFD, 11.4 +/- 1.9 in OR and 13.3 +/- 2.5 in OP rats. Similarly, citrate synthase activity in the heart, 59.3 +/- 7.2, and liver, 6.6 +/- 0.4, was also not significantly different among groups. Fatty acid composition of the gastrocnemius muscle was not significantly different among groups. Fasting glycogen levels in the liver, gastrocnemius muscle, and heart were 6.4 +/- 3.7, 13.2 +/- 2.3 and 6.8 +/- 1.9 mumol/g in LFD, 21.2 +/- 5.1 (p < 0.05 vs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue

Fat and carbohydrate overfeeding in humans: different effects on energy storage.

Both the amount and composition of food eaten influence body-weight regulation. The purpose of this study was to determine whether and by what mechanism excess dietary fat leads to greater fat accumulation than does excess dietary carbohydrate. We overfed isoenergetic amounts (50% above energy requirements) of fat and carbohydrate (for 14 d each) to nine lean and seven obese men. A whole-room calorimeter was used to measure energy expenditure and nutrient oxidation on days 0, 1, 7, and 14 of each overfeeding period. From energy and nutrient balances (intake-expenditure) we estimated the amount and composition of energy stored. Carbohydrate overfeeding produced progressive increases in carbohydrate oxidation and total energy expenditure resulting in 75-85% of excess energy being stored. Alternatively, fat overfeeding had minimal effects on fat oxidation and total energy expenditure, leading to storage of 90-95% of excess energy. Excess dietary fat leads to greater fat accumulation than does excess dietary carbohydrate, and the difference was greatest early in the overfeeding period.

Adolescent

Sugar and body weight regulation.

The need to understand reasons for the high prevalence of obesity in developed countries has led to examination of dietary habits that may contribute to obesity. We consider whether consumption of high amounts of sugars presents a public health problem by contributing to the development of obesity. Metabolic studies show that diets high in fat are more likely to result in body fat accumulation than are diets high in carbohydrate. There is no indication that simple sugars differ from complex sugars in this regard. Epidemiologic data show a clear inverse relation between intake of sugar and fat. Further, although high intake of dietary fat is positively associated with indexes of obesity, high intake of sugar is negatively associated with indexes of obesity. There is ample reason to associate high-fat diets with obesity but, at present, no reason to associate high-sugar diets with obesity.

Body Weight

Physical activity and energy requirements.

Differences in physical activity represent the largest source of variability in energy requirements, both within and between individuals. Chronic changes in physical activity can produce chronic changes in energy requirements that, if not compensated for, can lead to changes in the level at which body weight and body composition are maintained over time. We present a model that can serve as a framework for understanding how energy and macronutrient balance are maintained in steady state conditions, and for illustrating the potential effect of a change in physical activity on these steady state conditions and on energy requirements. According to the model, a chronic change in physical activity forces changes in other aspects of energy and substrate utilization so that a steady state condition can be reestablished. The net effects of the change in physical activity on energy requirements will depend on how and over what period of time these new steady states are reached. Although we cannot at present predict, for any individual, the precise effect of changes in physical activity on energy requirements and on body weight and composition, our model provides a framework for further study of the factors that can influence energy requirements.

Body Weight

Gender and Tanner stage differences in body composition and insulin sensitivity in early pubertal children.

A cross-sectional analysis examining the impact of gender and early pubertal stage on insulin sensitivity (Si) and body composition was carried out as part of a longitudinal study to determine how Si relates to body composition changes during puberty. The study population consisted of 97 healthy children (age range, 9.7-14.5 yr; 28 Tanner stage 2 boys, 25 stage 3 boys, 22 Tanner stage 2 girls, and 22 stage 3 girls). Si was determined by the modified minimal model of Bergman. Body fatness was assessed by body mass index (BMI), skinfold thickness, hydrodensitometry, and bioelectrical impedance. Results showed that stage 3 girls and stage 2 boys had significantly more body fat than stage 2 girls and stage 3 boys. Si was significantly lower (P < 0.02) and insulin-like growth factor-I levels higher (P < 0.006) in stage 3 girls compared to those in the other 3 groups. The best predictor of Si in all subjects was BMI (r2 = -0.63; P < 0.0001). In a stepwise multiple regression analysis, Si was best predicted from BMI, gender, and Tanner stage. According to this model, Si decreased as BMI increased and was lower in girls and Tanner stage 3 children. In boys, Si was best predicted from total fat mass and Tanner stage. In girls, Si correlated inversely with BMI, parental obesity, and insulin-like growth factor-I levels. Neither testosterone nor estradiol levels were associated with Si. These results demonstrate that Si, like body composition, has gender-dependent changes during puberty. It is, thus, possible that these pubertal changes in Si relate to changes in body composition.

Adipose Tissue

CD4+ T cell-dependent acquired state of immunity that protects the brain against Cryptococcus neoformans.

In immunodeficient hosts, a failure in defense mechanisms allows Cryptococcus neoformans to establish foci of infection in the brain. Immune and nonspecific responses in the primary site of infection in the lung have been described, but those extrapulmonary defense mechanisms that can be mobilized against the yeast have received little attention. This paper describes a response expressed against yeast in the brain of immunocompetent hosts, a response that is weakened in hosts deficient in CD4+ T cells. When a small number of yeast gain access to the vasculature, for example through an i.v. injection, about 0.1% establish themselves in the brain. Normal mice but not SCID mice have the capacity to suppress the multiplication of these yeast cells. The host response is accelerated in mice that are recovering from a primary lung infection, resulting in long term survival without antibiotic chemotherapy. This response is ablated by anti-CD4 mAb treatment and CD4+ cells obtained from infected primed donors are needed to confer immunity on SCID recipients. The critical target for the anti-Cryptococcus immune response are yeast in the brain cortex. However, rather than preventing the colonization of the brain by blood-borne yeast, immunity apparently serves to restrict the growth of yeast in a small number of established foci.

Animals

The opposing effects of insulin and hyperglycemia in modulating amino acid metabolism during a glucose tolerance test in lean and obese subjects.

An intravenous glucose tolerance test (IVGTT) was administered in both lean (n = 9) and obese (n = 14) volunteers to ascertain the importance of the dynamic interactions between insulin and glucose on plasma concentrations of two amino acids known to be primarily used by skeletal muscle, namely leucine and isoleucine, and one amino acid, phenylalanine, which is primarily metabolized by the liver. After a 30-minute basal period, each subject received a bolus injection of glucose (0.3 g/kg IV) followed 20 minutes later by a bolus injection of tolbutamide (300 mg). Blood samples were drawn frequently for 180 minutes after the glucose infusion to determine plasma concentrations of glucose, insulin, leucine, isoleucine, and phenylalanine. Plasma glucose and insulin concentrations during the basal period were increased by 10% and 100%, respectively, in obese compared with lean individuals (P < .05), whereas phenylalanine, isoleucine, and leucine levels were similar between groups. During the IVGTT, plasma glucose level initially increased by twofold and slowly returned to basal level thereafter, whereas insulin level responded to glucose and tolbutamide infusions in a typical biphasic manner. Plasma leucine and isoleucine levels did not change from basal levels during the first 60 minutes of the IVGTT as hyperglycemic hyperinsulinemia prevailed in both groups. However, when plasma glucose had returned to near-basal levels, plasma leucine and isoleucine levels began to decrease, reaching a plateau of approximately 20% and 35% below basal, and plasma insulin level remained elevated in the lean and obese individuals, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult

Time course of adaptation to a high-fat diet in obesity-resistant and obesity-prone rats.

The purpose of the present study was to characterize the time course of adaptation (i.e., circulating metabolites and hormones, fat pad mass, lipoprotein lipase) to a high-fat diet in obesity-prone (OP) and obesity-resistant (OR) male Wistar rats. Delineation of OP and OR was based on body weight gain (upper tertile for OP; lower tertile for OR) after 1 wk on a high-fat diet (60% of kcal from corn oil). Rats were killed after 1, 2, or 5 wk of the dietary period. Increased body weight and percent body fat in OP rats at 1 wk could not be accounted for by increased retroperitoneal or epididymal fat pad weight. Plasma nonesterified fatty acids and triglycerides, as well as blood concentrations of glucose, lactate, and glycerol, were similar throughout the study. Plasma insulin was significantly greater in OP vs. OR rats and low-fat diet (LFD; 20% of kcal from corn oil) controls at 5 wk only, and blood beta-hydroxybutyrate (mM) was significantly higher in OR compared with OP and LFD rats at 1, 2, and 5 wk. Lipoprotein lipase mRNA and activity were significantly greater in epididymal fat pad and significantly lower in gastrocnemius muscle of OP vs. OR rats at 1 wk. Results suggest that early (i.e., 1 wk) differences in body weight and fat weight between OP and OR rats are not due to fat deposition in retroperitoneal or epididymal fat depots, and tissue-specific changes in LPL (increase in epididymal fat pad and decrease in gastrocnemius muscle) that occur in OP compared with OR rats after 1 wk on a high-fat diet provide a metabolic environment favoring fat storage.

Adaptation, Physiological

Energy balance in endurance-trained female cyclists and untrained controls.

Reports of low energy intakes in trained female athletes imply they have an increased energetic efficiency. To address this question, we determined how energy balance was achieved in endurance-trained females cyclists and lean controls (n = 5 in each group). Daily energy expenditure was measured by using standardized physical activity protocols in a whole room calorimeter on two separate occasions: a cycling day and a noncycling day. Energy intake for weight maintenance was determined by a period of controlled feeding 5 days before and the day of each energy expenditure measurement. Energy balance was achieved in the cyclists on the cycling day while they consumed 2,900-3,000 kcal (their usual condition) and in controls on the noncycling day while they consumed 2,100-2,200 kcal (their usual condition). Total daily energy expenditure was not significantly different between the cyclists and controls on the noncycling day with both groups performing similar levels of activity. On the cycling day, daily energy expenditure was significantly greater in the cyclists vs. controls (P < 0.03) as a result of their greater amount of cycling activity. Components of daily energy expenditure, i.e., resting metabolic rate and thermic effect of food and activity (noncycling), were not significantly different between groups. Overall, we found no significant increase in the energetic efficiency of endurance-trained female cyclists compared with controls.

Adolescent