Lipid and lipoprotein distributions in children by ethnic group, gender, and geographic location--preliminary findings of the Child and Adolescent Trial for Cardiovascular Health (CATCH)

BACKGROUND

The Child and Adolescent Trial for Cardiovascular Health is a school-based study designed to test the effectiveness of dietary, physical activity, and educational interventions for reducing cardiovascular disease risk and teaching healthful behaviors to children.

METHODS

As part of a pilot phase in 1989, lipid, lipoprotein, and anthropometric measures were taken in black (n = 90), Hispanic (n = 68), and white (n = 265) 8- to 10-year-old schoolchildren in California, Louisiana, Minnesota, and Texas.

RESULTS

There were no significant differences in mean lipoprotein cholesterol values between fasting and nonfasting children. Therefore data from fasting and nonfasting children were pooled. Males and females within the same ethnic groups had similar mean levels of total cholesterol, low-density lipoprotein cholesterol, and very low-density lipoprotein cholesterol. However, levels of high-density lipoprotein cholesterol were higher among white and black males than among females from the same ethnic groups. Black males had higher total cholesterol than white males and higher high-density lipoprotein cholesterol than white males and Hispanic males. Similarly, black females had higher high-density lipoprotein cholesterol than white and Hispanic females. In all children combined high-density lipoprotein cholesterol was inversely correlated and low-density lipoprotein cholesterol was positively correlated with subscapular and tricep skinfold thickness, weight, and body mass index. There were significant differences in mean lipoprotein cholesterol levels between geographic sites. Total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were highest in children from California followed by children from Texas, Minnesota, and Louisiana.

CONCLUSION

Our results suggest that body fatness total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol differ in children by gender, ethnicity, and geographic location.

The effects of aerobic fitness on resting metabolic rate

A cross-sectional study was designed to determine the relationship between aerobic fitness and resting metabolic rate (RMR) in 69 males exhibiting a wide range of aerobic fitness levels (VO2max = 32.8-78.1 mL.kg-1.min-1). The results of this study indicated that RMR was not significantly different between trained and untrained individuals when expressed in kJ.kg fat-free weight-1.hr-1 or using an ANCOVA with fat-free weight as the covariate and RMR as the dependent variable (F ratio = 0.353, P less than 0.70). In addition, this study also failed to support a previously suggested hypothesis that an elevated RMR may only be observed in those individuals exhibiting both high VO2max values and currently training a minimum of 12-16 h/wk. Thus, the results of this study strongly suggest that RMR is independent of both a person's current aerobic level and training status.

The effects of either high-intensity resistance or endurance training on resting metabolic rate

The effects of either 12-wk of high-intensity endurance or resistance training on resting metabolic rate (RMR) were investigated in 47 males aged 18-35 y. Subjects were randomly assigned to either a control (C), resistance-trained (RT) or endurance-trained (ET) group. After training both exercise groups showed significant declines in relative body fat either by reducing their total fat weight and maintaining fat-free weight (ET) or by reducing their total fat weight and increasing fat-free weight (RT). RMR did not significantly change after either training regimen although a small decline in energy intake was observed along with an increase in energy expenditure [ET, 2.721 MJ (650 kcal) per training day]. These results suggest that both endurance and resistance training may help to prevent an attenuation in RMR normally observed during extended periods of negative energy balance (energy intake less than expenditure) by either preserving or increasing a person's fat-free weight.

Use of skinfolds and bioelectrical impedance for body composition assessment after weight reduction

The purpose of this study was to determine the accuracy of standard methods for estimating body composition in individuals who have undergone substantial and rapid weight loss. Subjects included 14 participants in a rapid weight reduction program using a very low-calorie diet, and 14 individuals of normal body composition matched with the obese group on the basis of gender, age, and height. Bioelectrical impedance (BI) and skinfold-derived estimates of relative body fat were compared with hydrostatic weighing in both groups. On the basis of mean values, standard errors of estimate (SEE) and simple correlations, none of the skinfold equations or the BI procedure were very accurate in the prediction of body fat in the group of weight-reduced obese patients. The Durnin-Rahaman (D-R) and Durnin-Womersley (D-W) equations were not significantly different from the hydrostatically determined values; however, correlations were low (r = 0.69 and 0.60). The Jackson-Pollock (J-P) equations and BI technique had high correlations (r = 0.78 and 0.89), but were significantly different from hydrostatic weighing. SEE for all equations and BI were high (greater than 4.5%). The control group was best predicted by the J-P equation (r = 0.88, SEE 3.5%, mean value of 21.2 +/- 4.3 vs 22.4 +/- 6.2%). BI and the D-R equation were also reasonably accurate. We conclude that additional research will be necessary to identify a predictive equation using skinfolds or BI that will provide more accurate estimates of relative body fat in individuals who have undergone substantial weight reduction in a relatively short period of time.

Is there energy conservation in amenorrheic compared with eumenorrheic distance runners?

The female distance runner is considered at high risk for secondary amenorrhea and reduced spinal bone mineral, and recent studies have suggested that these disturbances might be nutritionally or metabolically linked. The present study investigated 1) whether there is a physiological basis by which the amenorrheic runner might maintain weight at a lower than expected caloric intake, i.e., conservation of energy, and 2) the potential interactions of reduced energy intake, secondary amenorrhea, and reductions in bone density. Subjects included 13 elite female distance runners, 8 amenorrheic and 5 eumenorrheic, and 5 untrained female controls. Body composition by hydrostatic weighing, bone density and mineral content by dual-photon absorptiometry, and blood samples for hormonal analyses (once per week for 4 wk) were obtained, as were duplicate measures for resting metabolic rate, thermic effect of a meal, and the energy cost of specific (treadmill) and nonspecific (cycle ergometer) physical activity. Energy intake and energy expenditure were estimated by 3-day logs. Energy intakes did not differ (1,781, 1,690, and 1,763 kcal), nor did energy expenditures (2,480, 2,314, and 2,268 kcal), for the amenorrheic and eumenorrheic runner and control groups, respectively. The difference between reported energy intake and estimated energy expenditure of 500-700 kcal was likely due to underreporting or restricting intake, inasmuch as there was no evidence of energy conservation. A possible link was suggested between disordered eating, secondary amenorrhea, and bone mineral loss.

Relation of level of exercise, age, and weight-cycling history to weight and eating concerns in male and female runners

We examined the association between level of exercise and degree of weight preoccupation in a large sample of male and female runners, as well as risk factors posited to influence weight and eating concerns in the general population. Subjects were 2,459 males and 1,786 females who had completed a questionnaire on weight and eating concerns in a national running magazine. Eight percent of the males and 24% of the females had symptomatic scores on the Eating Attitudes Test (EAT). Exercise level, defined as weekly running mileage, was positively associated with excessive weight and eating concerns in males but not in females. Both sexes with a history of weight cycling were more likely to have symptomatic EAT scores than those with no such history. These results highlight the importance of studying these concerns in males as well as females and of examining the role of exercise level and weight-cycling history in the development of serious weight preoccupations.

Energy expenditure of elite female runners measured by respiratory chamber and doubly labeled water

To determine whether female athletes have unusually low energy requirements as suggested by many food intake studies, energy expenditure (EE) and intake were assessed in nine elite distance runners [26 +/- 3 (SD) yr, 53 +/- 4 kg, 12 +/- 3% body fat, and 66 +/- 4 ml.kg-1.min-1 maximal O2 uptake]. Subjects were admitted to a metabolic ward for 40 h during which 24-h sedentary EE was measured in a respiratory chamber. Free-living EE was then assessed by the doubly labeled water method for the next 6 days while the women recorded all food intake, daily body weight, and training mileage (10 +/- 3 miles/day). Energy intakes estimated from free-living EE (2,826 +/- 312 kcal/day) and body weight changes (-84 +/- 71 g/day) averaged 221 +/- 550 kcal/day in excess of those calculated from food records (2,193 +/- 466 kcal/day). The energy cost of training (1,087 +/- 244 kcal/day) was calculated as the difference between free-living EE and 24-h EE in the respiratory chamber (1,681 +/- 84 kcal/day) corrected for the thermic effect of food of the extra energy intake. These data do not support the hypothesis that training as a distance runner results in metabolic adaptations that lower energy requirements in women.

Eating and weight disorders in the female athlete

This paper presents an overview of eating disorders, including definitions, clinical criteria for appropriate diagnosis, and a discussion of the potential for increased risk for eating disorders in special populations of female athletes. This is followed by a discussion of the prevalence of eating disorders in normal and athletic populations. From this discussion, it seems clear that female athletes in endurance or appearance sports are at an increased risk for disordered eating. Finally, the paper focuses on related disorders--a triad associating eating disorders, menstrual dysfunction, and bone mineral disorders. It is clear that secondary amenorrhea is associated with malnutrition and disordered eating. Further, bone mineral disorders are related to menstrual dysfunction. Disordered eating may represent the initiating factor of this triad.

The aging of bone and muscle

The purpose of this article has been to summarize the existing body of literature on the changes in the function of muscle and bone that occur as a consequence of aging. Throughout this article, the importance of distinguishing between aging and disuse has been a recurring theme. Much of what had previously been considered aging is now regarded as functional disuse. With aging, muscle undergoes a reduction in size, and consequently strength, which is related to a loss of muscle fibers and a reduction in the size of existing fibers. There may be a selective loss of the Type II, or fast twitch fibers, but this is still under debate. This loss of muscle fibers is more than likely related to the loss of functional motor units. Muscle strength is reduced as a consequence of these changes, but there appears to be little loss in the metal olic potential of the muscle with aging. Exercise training can increase the size and strength of the trained muscles through hypertrophy of both Type I and II fibers and neural alterations but appears to have little effect on decreasing fiber number. Losses of bone start in the third and fourth decade of life, but the pattern of bone loss differs between cortical and trabecular bone, the former being less influenced by menstrual status. Exercise training appears to attenuate the normal decreases in bone with aging and can even lead to small increases in bone density and mass.

Stroke volume during submaximal exercise in endurance-trained normotensive subjects and in untrained hypertensive subjects with beta blockade (propranolol and pindolol)

The effect of beta-adrenergic blockade on stroke volume (SV) at increasing submaximal exercise intensities was studied in 12 endurance-trained normotensive and 12 untrained hypertensive (diastolic blood pressure greater than 95 mm Hg) men, aged 18 to 34 years. Subjects were assigned to each of 3 treatments in a double-blind, randomized order: placebo, propranolol (80 mg twice daily) and pindolol (10 mg twice daily) for 10 days, with a period of 48 to 60 hours from the initial dose to the first treadmill test and a 4-day washout period between drugs. Cardiac output was measured using the carbon dioxide rebreathing method and SV was calculated from cardiac output and heart rate as follows: SV = cardiac output/heart rate. Cardiac outputs were estimated at rest and while walking on a treadmill at 25, 45, 60 and 75% of the subject's previously determined maximal oxygen uptake (VO2max). No significant differences were found in cardiac output between either of the drugs and placebo at rest, or at any of the 4 rates of work. Propranolol significantly increased SV above placebo values (p less than 0.05) for both trained and untrained groups at the intensities of 45, 60 and 75%. Significant differences in SV were found between pindolol and placebo only at the intensities of 60 and 75% in the trained group. Contrary to expectations, SV showed no indication of a plateau with propranolol in the trained subjects throughout the 4 different exercise intensities, whereas a plateau was established under placebo conditions by 45% of VO2max in both trained and untrained subjects. These results suggest that both trained and untrained hypertensive persons can exercise with beta-adrenergic blockade at submaximal levels without compromised cardiac function.

The metabolic consequences of low and moderate intensity exercise with or without feeding in lean and borderline obese males

The purpose of this study was to investigate the role of exercise intensity on the post-exercise thermogenic effect (PETE), with or without feeding, in five lean (less than 15 percent body fat) and five borderline obese (between 20 and 25 percent body fat) individuals when the total caloric expenditure during exercise was equated to 720 kcal by adjusting exercise duration. Each subject participated in six testing sessions, including the measurement of resting metabolic rate (RMR), dietary induced thermogenesis (DIT) following a 720 kcal liquid meal, and four exercise trials including: (1) exercising on a treadmill at both 30 percent and 60 percent of VO2 max followed by a 720 kcal liquid meal (30F and 60F); and (2) exercising on a treadmill at both 30 percent and 60 percent of VO2 max followed by a non-caloric liquid meal substitute (water) matched by volume to the caloric liquid meal (30NF and 60NF). Indirect calorimetry was used to determine metabolic rate prior to each treatment (0-30 min RMR) and at 0-30, 50-60, 80-90, 110-120, 140-150, and 170-180 min following the feeding, exercise only, or exercise and feeding treatments. A significant difference in the post-exercise oxygen consumption was found between the two calorically equated exercise bouts (720 kcal) at 30 percent and 60 percent of each subject's VO2 max without feeding when all measurement periods following exercise were averaged together (60NF = 13.5 percent increase and 30NF = 5.5 percent). This difference was observed in both the lean and borderline obese subjects, with no significant difference between the two groups. In addition, when walking at either 30 percent or 60 percent of VO2 max preceded feeding, a significant attenuation in the rise of post-feeding RER values was observed in both groups with the higher exercise intensity showing the greatest RER attenuation when compared to the DIT trial. These results suggest that exercise intensity may play a significant role independent of the total energy expenditure in potentiating a person's post-exercise oxygen consumption rate and post-exercise substrate utilization for periods of up to 180 mins.

Changes in plasma free fatty acids and glycerols during prolonged exercise in trained and hypertensive persons taking propranolol and pindolol

The extent to which lipolysis is attenuated during prolonged submaximal exercise during beta blockade was determined in 12 normotensive endurance-trained and 12 hypertensive sedentary men using nonselective drugs with and without intrinsic sympathomimetic activity (ISA). Initially, subjects performed a graded treadmill test to determine maximal oxygen uptake (VO2max). This was followed by 2-hour walks at 25 and 45% of the subject's VO2max under each of 3 treatments: pindolol (ISA), propranolol (non-ISA) and placebo. The distribution of medication was randomized and double blinded. Blood samples taken at rest and every 30 minutes during the 2-hour walks were analyzed to determine the concentrations of free fatty acids (FFA) and glycerol. On the basis of the respective changes in FFA, glycerols and the respiratory exchange ratio, beta-adrenergic blockade did not attenuate lipolysis in the untrained hypertensive subjects when compared with the placebo administration. However, beta blockade did demonstrate a tendency to attenuate lipolysis in the trained, normotensive subjects when compared with results after placebo administration. This was particularly evident at 30 minutes of exercise, when both glycerol and FFA concentrations were not increased above resting values under both conditions of beta blockade. No differences between pindolol and propranolol were observed. Therefore, a beta-blocking agent with ISA properties appears to have no clear benefit with respect to lipid metabolism during low and moderate intensity exercise. Furthermore, these data demonstrate that beta blockade does not inhibit exercise-induced lipolysis at low and moderate intensities of exercise as formerly believed, and is unlikely to be the cause of fatigue normally observed during work in patient populations taking beta-blocking medication.

Estimation of minimal weight of adolescent males using multicomponent models

The purpose of this study was to determine whether the estimation of minimal weight (the body weight at which 5% of the weight is fat) of adolescent males could be improved by accounting for differences in hydration state and bone mineral content. Improvement was defined as a larger value for minimal weight and a smaller standard deviation compared to minimal weight estimated from body density. Forty adolescent males (mean age +/- SD, 15.5 +/- 1.4 yr) were measured for height, weight, body density (hydrostatic weighing), total body water (deuterium oxide dilution), and bone mineral content (single photon absorptiometry). Twenty-two adult males (mean age +/- SD, 23.6 +/- 2.2 yr) were measured as a reference group. Percent body fat and minimal weight were calculated from the body density (MWD), body density adjusted for total body water (MWDW), and body density adjusted for body water and bone mineral content (MWDWB). Repeated-measures ANOVA was used to test for differences between the methods and for trends in the data. The results showed a slight but nonsignificant increase in minimal weight for the adolescent group when body water and bone mineral data were added. The means +/- SD for MWD, MWDW, and MWDWB values of the adolescents were 54.6 +/- 9.0 kg, 54.8 +/- 8.6 kg, and 55.4 +/- 8.4 kg, respectively. It was concluded that the multicomponent methods, which accounted for hydration and bone mineral status, did not significantly improve the estimates of minimal weight of adolescent males compared to the single component method, i.e., minimal weight from body density.

Comparison of the effects of pindolol and propranolol on exercise performance in young men with systemic hypertension

To determine the effect of intrinsic sympathomimetic activity (ISA) on exercise performance during beta blockade, 12 hypertensive men were studied. The subjects underwent graded treadmill testing while taking pindolol (a beta blocker with ISA), propranolol (a beta blocker without ISA) and placebo, in a double-blind, crossover fashion. Blood pressure, heart rate, oxygen consumption (VO2), cardiac output and stroke volume were determined at 25, 45, 60 and 75% of each subject's VO2 max. Heart rate was significantly lower with pindolol compared with placebo at all stages of exercise, but significantly higher compared with propranolol at all stages of exercise except at 75% of VO2 max and at VO2 max (no significant differences between the 2 beta blockers were recorded at these stages). Mean arterial pressure was statistically equivalent with pindolol and propranolol at all stages of exercise and significantly lower while beta-blocked compared with placebo conditions at 45, 60 and 75% of VO2 max. Cardiac output and VO2 were statistically equivalent across all 3 treatments at all submaximal levels of exercise. It was concluded that, although heart rate was significantly higher with pindolol compared with propranolol at the 3 lower rates of work, cardiac output and VO2 were not different between the drugs, thus making little impact on exercise performance.

Alterations in plasma lipids consequent to endurance training and beta-blockade

Alterations in plasma lipids consequent to endurance training and beta-blockade. Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 288-292, 1989. The chronic use of beta adrenergic blockers (BAB) has been associated with reductions in HDL-cholesterol (HDL-C) and increases in triglycerides (TG). This study evaluated the impact of concurrent endurance exercise training and chronic medication with BAB on plasma lipid and lipoprotein profiles in healthy young adult males. Changes in plasma lipids and lipoproteins were investigated while exercise training under the influence of one of two nonselective BAB [sotalol (320 mg.d-1) and propranolol (160 mg.d-1)], one beta 1 selective BAB [atenolol (100 mg.d-1)], or a placebo control. Total cholesterol (TC), HDL-C, LDL-cholesterol (LDL-C), TG, and the ratios of TC/HDL and LDL/HDL were determined before and after endurance training programs of either 14 (N = 27, sotalol) or 15 (N = 47, propranolol/atenolol) wk duration. The subjects exhibited increases in maximal oxygen uptake of 12-20%. Despite increased endurance capacity, the subjects in both BAB and placebo control groups failed to demonstrate the expected increase in HDL-C and decrease in TG. In fact, HDL-C was significantly decreased post-training in the propranolol group. The placebo groups did decrease TC, LDL-C and the TC/HDL and LDL/HDL ratios, improving their CHD risk profile. Similar changes were not observed in the groups on BAB. Thus, with respect to the present population, BAB does appear to interfere with the usual training-induced improvements in the lipid profile. Endurance training may, however, reduce the deterioration in the lipid profile known to occur with BAB.