Biomedical subjects
Publications and source records attributed to John C Peters.
We continue to lose ground in meeting national goals for reversing obesity. We must begin to examine the social and economic drivers of this epidemic, and we must set more realistic, immediate goals. Success will depend on mounting an effective social movement fueled by renewal of American social capital.
The objective of this study was to determine whether vitamin supplementation during long-term (36 wk) ingestion of olestra supplemented with vitamin E could prevent decreases in vitamin E, vitamin A, and carotenoids. This was a 36-wk study of 37 healthy males randomly assigned to consume a control diet composed of 33% energy from fat, a similar diet in which one third of the energy from fat had been replaced with olestra, or a fat-reduced (25% of energy from fat) diet. Subjects also ingested a daily multivitamin (Centrum). Serum concentrations of alpha-tocopherol, retinol, beta-carotene, lycopene, and lutein + zeaxanthin were analyzed by HPLC. Subjects eating the olestra-containing diet had substantial decreases in serum beta-carotene, lycopene, and lutein + zeaxanthin, which occurred by 12 wk; these changes were found despite correcting for serum total cholesterol or BMI. Serum beta-carotene and lycopene concentrations were below the lower limit of the reference range (<0.186 and <0.298 mumol/L, respectively) at one or more time points. The slight decline in serum alpha-tocopherol concentration, significant at 24 wk, was caused by the decline in serum cholesterol. Retinol concentrations decreased with time in all 3 groups, but were not affected by olestra. We conclude that supplementation with a multivitamin containing vitamins A and E was adequate to prevent olestra-induced decrease in serum alpha-tocopherol and retinol. Olestra-induced decreases in serum beta-carotene, lycopene, and lutein + zeaxanthin were not prevented by the vitamin supplement used in this study.
INTRODUCTION: There is an urgent need to increase the physical activity in the population. Small-scale success has been achieved in programs like Colorado on the Move (COM), an obesity prevention program using electronic pedometers. METHODS: To provide baseline information for COM, this first-ever statewide survey of walking was conducted with 1098 individuals. The weighted mean BMI was 25.3 +/- 0.18 kg x m(-2), and mean age was 44 +/- 0.42 yr of age. Subjects participated in a short telephone interview and then were sent a pedometer to wear for four consecutive days. A total of 742 of the 1098 subjects completed the pedometer phase. RESULTS: The average adult in Colorado reported taking 6804 steps per day. About 33% reported taking fewer than 5000 steps per day, and only 16% reported taking 10,000 or more steps per day. Steps per day increased with other self-reported measures of physical activity (P = 0.0001) and decreased with self-reported inactivity (P = 0.0001). Significant determinants of steps per day included increasing age (negative, P = 0.001), marital status (positive for single status, P = 0.05), income (positive for incomes of dollar 25,000 to dollar 99,000, P = 0.003), and increasing BMI (negative for BMI > or = 30 kg x m(-2), P = 0.000). Obese individuals (BMI > or = 30 kg x m(-2)) walked about 2000 fewer steps per day than normal-weight individuals. These results provide the first population data on current walking levels, on how this relates to self-reported physical activity, and on determinants of walking. Results also provide a baseline level of walking for future evaluation of COM. CONCLUSION: Increasing steps per day appears to be a good target to use in interventions to increase physical activity. Even in Colorado, one of the leanest states, very low levels of physical activity are seen in much of the population.
Seven nonobese adult females (40 +/- 8 years) were studied in a room calorimeter on a day that resistance exercise (REX) was performed (4 sets of 10 exercises) and on a nonexercise control day (CON). Twenty-four-hour energy expenditure (EE) on the REX day (mean +/- SD, 2,328 +/- 327 kcal.d(-1)) was greater than CON (2,001 +/- 369 kcal.d(-1), p < 0.001). The net increase in EE during and immediately after (30 minutes) exercise represented 76 +/- 12% of the total increase in 24-hour EE. Twenty four-hour RQ on the REX day (0.86 +/- 0.06) did not differ from CON (0.87 +/- 0.02). Twenty four-hour carbohydrate oxidation was elevated on the REX day, but 24-hour fat and protein oxidation were not different. Thus, in women, the increase in EE due to resistance exercise is largely seen during and immediately after the exercise. The increased energy demand is met by increased carbohydrate oxidation, with no increase in 24-hour fat oxidation.
Obesity is reaching epidemic proportions and predisposes afflicted individuals to several comorbidities. For these individuals, losing weight has proven to be an easier feat than maintaining a reduced weight. In obesity-prone rats, we examined if there is a metabolic propensity to regain weight after a period of significant weight loss. Twenty-four-hour energy expenditure (EE), sleeping metabolic rate (SMR), and nonprotein respiratory quotient (NPRQ) were obtained by indirect calorimetry with urinary nitrogen analysis and normalized to fat mass (FM) and fat-free mass (FFM) acquired by dual-energy X-ray absorptiometry. Obesity-prone rats were examined after free access to a high-fat diet for 16 wk to establish the obese state. They were again examined after 2 wk of calorie restriction, which reduced body weight (14%) and FM (32%). Rats were again examined after a further 8 wk of intake-regulated weight maintenance or ad libitum feeding that led to weight regain. Metabolic data were compared with preobese and age-matched controls. Weight loss suppressed EE and SMR beyond what was expected for the change in metabolic mass. This elevated metabolic efficiency persisted throughout weight maintenance but resolved after 8 wk of regain. Adjusted NPRQ values were elevated in weight-maintained and weight-regaining rats, suggesting a preference for carbohydrate utilization. These data support the concept that weight reduction in obesity is accompanied by metabolic adjustments beyond the drive to consume calories that predispose to weight regain, and some aspects of this adjustment persist with prolonged weight maintenance and during weight regain.
Poor nutrition and physical inactivity are among the leading causes of morbidity and mortality in the United States, and widespread behavior modification is needed to improve health now and in the future. There is growing evidence that modifications in the physical environment and in social policies will be required to accomplish this goal. There is also growing recognition that economic factors have contributed to current eating and physical activity patterns, and that economic factors need to be considered when developing strategies for improving these behaviors. Identifying where economic and public health priorities converge could suggest new avenues for sustainable policy changes, which will, in turn, promote healthy choices on both an individual and population-wide level. To review the effect that economics has on eating and physical activity behaviors, the Partnership to Promote Healthy Eating and Active Living convened an Economic Analysis Forum. Two working groups were formed-one focusing on eating behaviors and one on physical activity, and both with equal representation from health-related and economic disciplines. The groups examined how economics has contributed to present eating and physical activity patterns and how economics could be used to develop interventions to improve these patterns. This article describes the challenges the groups faced in their work, the way in which the public health and economic approaches were integrated, and the questions left unanswered.
We have previously shown that the C57BL/6J (B6) mouse will develop obesity and diabetes if raised on a high-fat diet. Because high fat feeding is associated with hyperphagia, the present study was designed to separate the effects of fat from those of excess caloric consumption in this animal model. B6 mice were fed a low-fat diet (LF group) diet, high-fat diet (HF group) diet, or high-fat-restricted diet (HFR group), in which intake animals were pair-fed a high-fat diet to caloric level consumed by LF for 11 weeks. Within 3 weeks, HFR were significantly heavier than LF and, after 11 weeks, weight and glucose levels, but not insulin, were significantly increased in HFR when compared to LF. Body composition analysis showed the weight increase in HFR arose from an increase in percent fat consumed. We conclude that reducing the number of kilocalories consumed from a high-fat diet attenuates but does not prevent the development of type 2 diabetes and obesity in the B6 mouse.
BACKGROUND: Many commercially available pedometers undercount, especially at slower speeds. We examined the effects of age, obesity, and self-selected walking speed on pedometer accuracy. We also compared the accuracy of piezoelectric and spring-levered pedometers at slow walking speeds. METHODS: Study 1: 259 subjects walked on a motorized treadmill at two self-selected walking speeds. Steps were counted using a spring-levered pedometer. Study 2: 32 subjects walked on a motorized treadmill at slow walking (1.0-2.6 MPH) speeds. Steps were counted using spring-levered and piezoelectric pedometers. RESULTS: Study 1: self-selected walking speed and pedometer accuracy decreased with increasing age, weight, and body mass index (BMI). Accuracy was 71% below 2.0 MPH, 74-91% between 2.0 and 3.0 MPH, and 96% above 3.0 MPH. Decreased accuracy was best predicted by increasing age. Study 2: between 1.8 and 2.0 MPH, the accuracy of the piezoelectric pedometer (>97%) exceeded that of the spring-levered pedometers (52-95%). Even at 1.0 MPH, accuracy of the piezoelectric pedometer (56.4 +/- 33.8%) was superior to the spring-levered pedometers (7-20%). CONCLUSION: Accuracy of all pedometers tested exceeded 96% at speeds 3.0 MPH, but decreased at slower walking speeds. In individuals that naturally ambulate at slower walking speeds (e.g., elderly), we recommend the use of more sensitive (e.g., piezoelectric) pedometers.
The obesity epidemic shows no signs of abating. There is an urgent need to push back against the environmental forces that are producing gradual weight gain in the population. Using data from national surveys, we estimate that affecting energy balance by 100 kilocalories per day (by a combination of reductions in energy intake and increases in physical activity) could prevent weight gain in most of the population. This can be achieved by small changes in behavior, such as 15 minutes per day of walking or eating a few less bites at each meal. Having a specific behavioral target for the prevention of weight gain may be key to arresting the obesity epidemic.
The global obesity epidemic has heightened the debate about dietary factors contributing to weight gain. Media stories have promulgated the notion that obesity has increased despite reductions in dietary fat intake. Some have even speculated that lower dietary fat levels may be driving the rapid rise in weight gain within the population. A close examination of the science reveals a different picture and supports the hypothesis that dietary fat, within the context of the total dietary composition consumed by many populations, promotes obesity. Hence, dietary fat control is still an important strategy as part of an overall approach to body weight management in our modern environment. Dietary fat increases the energy density of foods. Abundant evidence from preclinical and clinical studies indicates that fat promotes excess energy intake and positive energy balance. Dietary fat does not promote its own oxidation in the body and is stored efficiently, promoting a positive fat balance. Thus, both the behavioral and metabolic responses to dietary fat increase the probability of positive energy balance and body fat gain. Restoring fat balance when consuming diets rich in fat requires increasing the size of the body fat mass, increasing physical activity, or reducing dietary fat intake. Numerous epidemiologic, preclinical, and controlled clinical studies have shown that body fat is positively associated with dietary fat intake and that dietary fat manipulation leads to appropriate changes in body fat mass. Finally, data from the National Weight Control Registry, a database of > 3000 individuals who have successfully maintained a substantial weight loss, indicate that moderating dietary fat intake is a key strategy for long-term management of body weight.
OBJECTIVES: There is considerable controversy regarding the effects of fat substitutes (such as the non-caloric fat substitute, olestra) on Americans' diet and health. This report gives associations of olestra consumption (in savory snacks) with changes in nutrient intake, serum lipid concentrations, and body weight 1 y after these snacks became available nationally in the United States. METHODS: Participants were 1178 adults recruited from three large U.S. cities. At baseline (before the availability of olestra), participants attended a clinic visit and completed questionnaires (including a food-frequency questionnaire), provided fasting blood samples, and had height and weight measured. The clinic visit was repeated about 1 y later, after the introduction of olestra-containing snacks in the marketplace. Olestra consumption was categorized as "none," "very low" (>0 to <0.4 g/d), "low" (>/=0.4 to <2.0 g/d), and "moderate/high" (>/=2.0 g/d). RESULTS: Twenty-five percent of participants reported consuming olestra-containing savory snacks in the preceding month, but only 2% were categorized as moderate/high consumers. Men reported nearly twice as much olestra consumption as women (1.22 versus 0.68 g/d, P = 0.01). Among moderate/high olestra consumers, total energy and carbohydrate intakes increased by 209 kcal/d and 37 g/d, compared with decreases of 87 kcal/d and 14 g/d, respectively, among non-consumers (both Ps for trend = 0.01), corresponding to non-significant changes in percentages of energy from carbohydrate and total fat. Olestra consumption was not associated with statistically significant changes in serum lipids or body weight. CONCLUSIONS: This study found very modest changes in total diet, but no changes in serum lipids or body weight, associated with consumption of olestra-containing savory snacks. However, the low use of olestra by the study sample limited the ability of this study to detect significant effects.
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Obesity has reached epidemic proportions in many countries around the world. Because of the close relationship between obesity and type 2 diabetes, an epidemic of diabetes is close behind the obesity epidemic. Preventing and treating obesity is becoming an increasing priority. In the United States, over 60 % of the adult population is overweight or obese and thus at increased risk of developing diabetes and cardiovascular disease. While the aetiology of obesity and diabetes is complex, diet clearly plays an important role both in the development and management of these diseases. There is interest in functional foods that could help in prevention and/or management of obesity and type 2 diabetes. This could involve food products that help management of 'hunger' or that increase 'satiety'. It could also involve foods that contribute to more inefficient use of ingested energy (i.e. foods that stimulate energy expenditure more than would be expected from their energy content). As the concept of insulin sensitivity becomes generally more accepted by health care professionals and the public, foods may be targeted towards maximizing insulin sensitivity and towards 'prevention' of diabetes. In addition to foods that impact upon body weight, these may include foods that affect the glucose and/or insulin levels that are seen either following the ingestion of food or later in the day. The present paper reviews the complex aetiology of obesity and diabetes and considers a potential role for functional foods in prevention and treatment of obesity and diabetes.
OBJECTIVE: To examine in two separate studies the effects of replacing dietary fat with Olestra on body composition and weight change in healthy young men and women. METHODS: Ten healthy, lean young men participated in Study One that was a 22-day single blind, within-subject design. After a control diet (40% fat) for eight days Study One subjects received an Olestra-substituted diet (31% metabolizable fat) for 14 days. Study Two was a randomized parallel-arm clinical trial with 15 healthy, lean and overweight young women. These subjects were randomly assigned to receive a control diet (40% fat), an Olestra-containing diet (31% metabolizable fat) or a reduced-fat diet (31% fat) for 10 weeks. All foods were provided to the subjects, and energy intakes were not restricted. The primary endpoint in both studies was change from baseline in body weight. In Study Two, body composition was measured by dual energy x-ray absorptiometry. In both studies, food intake and nutrient compensation were assessed. RESULTS: In Study One fat substitution by Olestra resulted in a significant 1.7 kg weight loss from baseline. In Study Two, change in body weight and body fat from baseline were statistically significant in all groups, but the group with Olestra lost significantly more weight from baseline (-5.0 kg) than the other two groups. In Study One there was partial compensation for the decreased energy intake, while in Study Two, compensation was seen only for those on the reduced-fat diet. CONCLUSION: Replacement of 1/3 of dietary fat with Olestra in periods of up to 10 weeks results in weight loss in men and women.
BACKGROUND: Dietary fat has been implicated as a risk factor for cardiovascular disease and obesity. OBJECTIVE: We evaluated the effect on body weight, body fat, lipids, glucose, and insulin of replacing dietary fat with olestra in moderately obese men. DESIGN: Forty-five healthy overweight men were randomly assigned to 1 of 3 diets: control diet (33% fat), fat-reduced diet (25% fat), or fat-substituted diet (one-third of dietary fat replaced by olestra to achieve a diet containing 25% metabolizable fat). Body fat was measured by dual-energy X-ray absorptiometry and visceral and subcutaneous abdominal fat by computed tomography. RESULTS: Thirty-six men completed the 9-mo study. Body weight and body fat in the fat-substituted group declined by a mean (+/- SEM) of 6.27 +/- 1.66 and 5.85 +/- 1.34 kg, respectively, over 9 mo compared with 3.8 +/- 1.34 and 3.45 +/- 1.0 kg in the control group and 1.79 +/- 0.81 and 1.68 +/- 0.75 kg in the fat-reduced diet group. At 9 mo, the mean difference in body fat between the fat-reduced and fat-substituted groups was -4.19 +/- 1.19 kg (95% CI: -6.57, -1.81), that between the control and fat-substituted groups was -2.55 +/- 1.21 kg (-0.13, -4.97), and that between the control and fat-reduced groups was 1.63 +/- 1.18 kg (3.96, -0.70). The men eating the fat-reduced diet asked for almost no extra foods, in contrast with the significantly higher requests (P < 0.05) from both of the other 2 groups. CONCLUSION: Replacement of dietary fat with olestra reduces body weight and total body fat when compared with a 25%-fat diet or a control diet containing 33% fat.
BACKGROUND: Whether resistance exercise is as effective as aerobic exercise for body-weight management is debated. PURPOSE: To compare 24-h energy expenditure (EE) and macronutrient oxidation elicited by comparable bouts of stationary cycling (BK) and weightlifting (WTS). METHODS: 24-h EE and macronutrient oxidation were measured in 10 nonobese male subjects on three occasions using whole-room indirect calorimetry. BK and WTS days were compared with a nonexercise control day (Con). RESULTS: During BK, subjects exercised for 49 +/- 7 min (mean +/- SEM) at 70% of OV(2max) and expended 546 +/- 16 kcal. During WTS, subjects performed a 70-min circuit consisting of four sets of 10 different exercises at 70% of exercise-specific 1-repetition maximum and expended 448 +/- 21 kcal (P < 0.001 vs BK). 24-h EE on BK and WTS days (2,787 +/- 76 kcal x d(-1), 2,730 +/- 106 kcal x d(-1), respectively, P > 0.05) was elevated compared with Con (2,260 +/- 96 kcal x d(-1), P < 0.001), but 24-h respiratory exchange ratio (RER) was not different. 24-h carbohydrate oxidation was significantly elevated on the exercise days (BK = 370 +/- 18 g x d(-1), WTS = 349 +/- 23 g x d(-1), P > 0.05) compared with Con (249 +/- 29 g x d(-1), P = 0.04). 24-h fat and protein oxidation were the same on BK, WTS, and Con days. EE and macronutrient oxidation in the periods after exercise also did not differ across conditions. CONCLUSION: In men, resistance exercise has a similar effect on 24-h EE and macronutrient oxidation as a comparable bout of aerobic exercise. Neither exercise produced an increase in 24-h fat oxidation above that observed on a nonexercise control day.