Energy expenditure and substrate oxidation predict changes in body fat in children

Physiological response during exercise is preserved in children exposed to a suboptimal gestational environment

OBJECTIVE

This study investigated whether exposure to suboptimal gestational factors (SGFs) alters mechanical efficiency (ME) and substrate oxidation during rest and exercise in children as a mechanism contributing to obesity.

METHODS

Data from the Quebec Adiposity and Lifestyle Investigation in Youth cohort were used. Children aged 8 to 10 years performed an incremental maximal cycling test with indirect calorimetry. Their ME was measured during submaximal and maximal effort. The substrate oxidation during rest and submaximal effort was also computed. ME and substrate oxidation results between children exposed to each SGF during pregnancy (gestational diabetes mellitus: n = 68; hypertensive disorders: n = 49; maternal smoking: n = 77) and nonexposed children (n = 370) were compared.

RESULTS

No difference was observed for ME during submaximal (F[3,540] = 0.46, p = 0.713) and maximal effort (F[3,545] = 0.86, p = 0.463) between exposed and nonexposed children. The percentage contributions of lipids and carbohydrates did not differ during rest (F[3,545] =1.68, p = 0.169) or submaximal exercise (F[3,544] = 0.31, p = 0.534) between exposed and nonexposed children.

CONCLUSIONS

Children exposed to investigated SGFs display a similar physiological response regarding ME and substrate oxidation during rest and exercise compared to nonexposed children. Future studies should confirm these novel results and continue investigating other research avenues to explain the higher risk of obesity in this population.

Longitudinal analysis of resting energy expenditure and body mass composition in physically active children and adolescents

Background

Monitoring body composition and changes in energy expenditure during maturation and growth is significant, as many components can influence body structure in adulthood. In the case of young players, when these changes can influence their strength and power, it seems to be equally important. Our aim was to examine whether resting energy expenditure (REE) and body composition would change after 10 months from baseline in physically active children and adolescents.

Methods

We obtained data from 80 children and adolescents aged 9 to 17 years at two measurement points: the baseline in September 2018 and after 10 months in July 2019. The study was carried out using a calorimeter (Fitmate MED, Cosmed, Rome, Italy), a device used to assess body composition using by the electrical bioimpedance method by means of a segment analyzer (TANITA MC-980). The Student’s t-test and linear regression analysis were used. Using the stepwise forward regression procedure, the selection of factors in a statistically significant way that describes the level of REE was made.

Results

We noticed that REE was not significantly different between baseline (1596.94 ± 273.01 kcal) and after 10 months (1625.38 ± 253.26 kcal). When analyzing the difference in REE between studies girls, we found body height as a significant predictor. The results of our study show a negative relationship between growth and REE. Differences between sexes and age in REE between baseline and after 10 months were not significant.

Conclusions

Our study involving physically active children and adolescents, which used repeated objective measures and longitudinal statistical modeling to analyze them, was unable to demonstrate any interaction between body weight change, body composition measurements, and REE.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-022-03326-x.

Total energy expenditure is repeatable in adults but not associated with short-term changes in body composition

Low total energy expenditure (TEE, MJ/d) has been a hypothesized risk factor for weight gain, but repeatability of TEE, a critical variable in longitudinal studies of energy balance, is understudied. We examine repeated doubly labeled water (DLW) measurements of TEE in 348 adults and 47 children from the IAEA DLW Database (mean ± SD time interval: 1.9 ± 2.9 y) to assess repeatability of TEE, and to examine if TEE adjusted for age, sex, fat-free mass, and fat mass is associated with changes in weight or body composition. Here, we report that repeatability of TEE is high for adults, but not children. Bivariate Bayesian mixed models show no among or within-individual correlation between body composition (fat mass or percentage) and unadjusted TEE in adults. For adults aged 20-60 y (N = 267; time interval: 7.4 ± 12.2 weeks), increases in adjusted TEE are associated with weight gain but not with changes in body composition; results are similar for subjects with intervals >4 weeks (N = 53; 29.1 ± 12.8 weeks). This suggests low TEE is not a risk factor for, and high TEE is not protective against, weight or body fat gain over the time intervals tested.

Maternal and child factors associated with child body fatness in a Ghanaian cohort

OBJECTIVE

We aimed to identify factors (child diet, physical activity; maternal BMI) associated with body composition of Ghanaian pre-school children.

DESIGN

Longitudinal analysis of the International Lipid-Based Nutrient Supplements (iLiNS)-DYAD-Ghana randomized trial, which enrolled 1320 pregnant women at ≤20 weeks' gestation and followed them and their infants until 6 and 18 months postpartum, respectively. At follow-up, child age 4-6 years, we collected data on body composition (by 2H dilution), physical activity and diet, extracted dietary patterns using factor analysis, and examined the association of children's percentage body fat with maternal and child factors by regression analysis.

SETTING

Eastern Region, Ghana.

PARTICIPANTS

Children 4-6 years of age.

RESULTS

The analysis included 889 children with percentage body fat and dietary data at follow-up. We identified two major dietary patterns, a snacking and a cooked foods pattern. Percentage body fat was positively associated (standardized β (se)) with maternal BMI at follow-up (0·10 (0·03); P = 0·003) and negatively associated with physical activity (-0·15 (0·05); P = 0·003, unadjusted for child gender), but not associated with the snacking (0·06 (0·03); P = 0·103) or cooked foods (-0·05 (0·07); P = 0·474) pattern. Boys were more active than girls (1470 v. 1314 mean vector magnitude counts/min; P < 0·0001) and had lower percentage body fat (13·8 v. 16·9 %; P < 0·0001).

CONCLUSIONS

In this population, maternal overweight and child physical activity, especially among girls, may be key factors for addressing child overweight/obesity. We did not demonstrate a relationship between the dietary patterns and body fatness, which may be related to limitations of the dietary data available.

Low capacity to oxidize fat and body weight

For a given positive energy balance, a low capacity to oxidize fat could contribute to weight gain (low fat oxidation hypothesis). This hypothesis is based on the arguments that for a given stable diet and food quotient (FQ), the respiratory quotient (RQ) is higher in obesity prone (OP) than in obesity resistant individuals (OR) and that a high RQ predicts higher future weight gain. A review of 42 studies shows that there is no convincing experimental support to these arguments and thus for the low fat oxidation hypothesis. A power analysis also shows that this hypothesis might be impossible to experimentally confirm because very large numbers of subjects would be needed to reject the null hypotheses that the 24-h RQ is not different in OP and OR or that future weight gain is not different in individuals with a low and high 24-h RQ at baseline. A re-examination of the significance of the 24-hour and fasting RQ also shows that the assumption underlying the low fat oxidation hypothesis that a high RQ reflects a low capacity to oxidize fat is not valid: For a stable diet, the 24-h RQ entirely depends on FQ and energy balance, and the fasting RQ mainly depends on the FQ and energy balance and on the size of glycogen stores.

School-based study found that physical activity and aerobic fitness predicted increases in total body fat and abdominal fat at a mean age of 9.8 years

AIM

We assessed whether baseline measurements of physical activity, aerobic fitness, body fat and abdominal fat were predictors of changes in body fat measurements over a two-year period.

METHODS

The study comprised of 204 children aged 9.8 ± 0.6 years with a normal body mass distribution, who recruited from four schools in middle-class areas of Malmö, Sweden, from 2001 to 2004. Peak oxygen uptake and physical activity were measured at baseline. Body fat was measured by dual-energy X-ray absorptiometry at baseline and two years later.

RESULTS

Physical activity, aerobic fitness and total body fat or abdominal fat were predictors of change in total body fat or abdominal fat over a period of two years. Changes in the percentage of body fat were not related to any of the baseline measurements.

CONCLUSION

Our two-year follow-up of children with a mean age of 9.8 years at baseline showed that physical activity, aerobic fitness and body fat or abdominal fat predicted changes in total body fat or abdominal fat, but not the percentage of body fat.

Comparison of daily physical activity parameters using objective methods between overweight and normal-weight children

PURPOSE

The purpose of the present study was to determine if there were any differences in various aspects of physical activity such as energy expenditure, intensity, and type of activity between normal-weight and overweight boys.

METHODS

Children aged 9-12 years were recruited from 2 elementary schools located in different urban districts in Republic of Korea. The present study included 45 Korean boys, of which 19 were normal-weight and 26 were overweight. Daily physical activity was estimated over the same 1-week study period under free-living conditions using the doubly labeled water (DLW) method and a tri-axial accelerometer. Resting metabolic rate (RMR) was measured using the Douglas bag method and open-circuit indirect calorimetry. We calculated the physical activity level (PAL) as the total energy expenditure (TEE)/RMR.

RESULTS

PAL was not significantly different between the groups. In the accelerometer data, time spent in locomotive moderate-to-vigorous physical activity (MVPA) was significantly lower in overweight boys than in normal-weight subjects, whereas other variables including non-locomotive activity did not differ between groups. In addition, among all participants, time spent in total locomotive activity was significantly associated with PAL. Time spent in locomotive MVPA was significantly associated with PAL.

CONCLUSION

Overweight boys may be less physically active based on locomotive MVPA, which was positively related with PAL. Our findings suggest that the contribution of locomotive MVPA to the increase in PAL was relatively significant.

High energy expenditure is not protective against increased adiposity in children

BACKGROUND

Low levels of energy expenditure (TEE) may contribute to excess weight during childhood, but limited longitudinal data exist.

OBJECTIVES

This is to test whether low TEE during the first 6 years of life could predict excess weight status at 8 years.

METHODS

Total energy expenditure from doubly labelled water, weight, stature, waist circumference and fat mass and fat-free mass (FFM) in children at 0.25, 2, 4 and 6 years of age. This cohort includes individuals at high (n = 27) and low risk (n = 26) for childhood obesity, based upon whether pre-pregnant maternal obesity. A linear mixed effects model was fit to TEE. Individual variation was accounted for as a random effect. Residual TEE was calculated for age and individually averaged across time.

RESULTS

Fat-free mass (kg) was highly correlated (R²  = 0.91) with TEE (kcal/day), and waist circumference and sex were also significant predictors of TEE. TEE residual tracked within individuals. TEE residuals did not correlate with either BMI or %fat at age 8 years.

CONCLUSION

Using the residual TEE approach to identify high and low TEE during the first 6 years of life did not explain excess weight at 8 years of life in this cohort of children at high and low risk of obesity based upon maternal obesity status.

Objectively measured physical activity and longitudinal changes in adolescent body fatness: an observational cohort study

BACKGROUND

The data regarding prospective associations between physical activity (PA) and adiposity in youth are inconsistent.

OBJECTIVE

The objective of this study was to investigate associations between baseline levels of objectively measured PA and changes in adiposity over 2.5 years from mid-to-late adolescence.

METHODS

This was an observational cohort study in 728 school students (43% boys) from Cambridgeshire, United Kingdom. Fat mass index (FMI, kg m(-2) ) was estimated at baseline (mean ± standard deviation age: 15 ± 0.3 years) and follow-up (17.5 ± 0.3 years) by anthropometry and bioelectrical impedance. Habitual PA was assessed at baseline by ≥3 d combined heart rate and movement sensing. Average daily PA energy expenditure (PAEE) and the time (min d(-1) ) spent in light, moderate and vigorous intensity PA (LPA, MPA and VPA, respectively) was estimated. Multilevel models were used to investigate associations between baseline PA and change in FMI (ΔFMI). Adjustment for baseline age, sex, follow-up duration, area-level socioeconomic status, season of PA assessment, sedentary time, energy intake and sleep duration was made; baseline FMI was also added in a second model.

RESULTS

FMI increased significantly over follow-up (0.6 ± 1.2 kg m(-2) , P < 0.001). Baseline PAEE and LPA positively predicted ΔFMI in overfat participants (P ≤ 0.030), as did VPA in initially normal fat participants (P ≤ 0.044). There were further positive associations between PAEE and ΔFMI in normal fat participants, and between MPA and ΔFMI in both fat groups, when adjusted for baseline FMI (P ≤ 0.024).

CONCLUSIONS

Baseline PAEE and its subcomponents were positively associated with small and unlikely clinically relevant increases in ΔFMI. These counter-intuitive findings may be explained by behavioural changes during the course of study follow-up.

Growth retardation at early life and metabolic adaptation among North Korean children

The high prevalence of obesity is a major public health issue and contributes to the 'double burden' of disease in developing countries. Early exposure to poor nutrition may cause metabolic adaptations that, when accompanied by exposure to 'affluent' nutrition, may increase the risk for obesity and other metabolic disorders. The aim of this study was to determine differences in energy metabolism and nutritional status between normal-height and growth-retarded North Korean children living in South Korea. A total of 29 children were recruited and underwent measurements of resting energy expenditure (REE), respiratory quotient (RQ), anthropometrics and dietary intake. There was no difference in REE or any assessment of obesity between the growth-retarded and normal-height children. Children who were classified as growth retarded (HAZ<-1.0) or stunted (HAZ<-2.0) had a significantly higher RQ (β=0.036 or 0.060, respectively, P=0.018 or 0.016), independent of sex, age, fat-free mass, fat mass and food quotient, compared with children with normal height. The results from this study, the first from an Asian population, add to the growing body of literature suggesting that undernutrition early in life results in adaptations in energy metabolism that favor fat deposition, increasing the risk of stunted children becoming overweight or obese later in life. Continued research on this topic is warranted, given the continued rise in the prevalence of the double burden in transitional countries.

Dietary fat intake, body composition and blood lipids of university men and women

BACKGROUND

Cardiovascular disease rates are high in the U.K., particular in men, and are related to dietary fat intake. We conducted a pilot study to investigate relationships between saturated and unsaturated dietary fat intakes, body composition and blood lipid parameters in Caucasian men and women at university.

METHODS

Volunteers (52 men and 52 women; age range 20-50 years) were recruited from staff and students of London Metropolitan University. Dietary intake, body composition, blood pressure and fasting blood glucose and lipids were assessed. Gender differences between the measured variables and their relationships were assessed by Mann-Whitney U-test, and by multi-linear (stepwise) regression, respectively.

RESULTS

Men consumed more saturated fat (29.5 vs. 20.5 g/day, p < 0.001), and had elevated levels of glucose (5.34 + 0.74 vs. 4.85 + 0.49 mmol/l, p < 0.001), low-density lipoprotein (LDL) cholesterol (2.99 + 1.5 vs. 2.62+ 0.74 mmol/l, p < 0.05), systolic blood pressure (126.4 + 11.0 vs. 112.6 + 17.2 mm/Hg, p < 0.001), and lower high-density lipoprotein (HDL) cholesterol (1.41 ± 0.34 vs. 1.83 ± 0.43, p < 0.001). Saturated fat was positively associated with total body fat ( p < 0.05), trunk fat ( p < 0.001), HDL cholesterol ( p < 0.05) and systolic blood pressure ( p < 0.001) in women, while in men docosahexaenoic acid and total cholesterol ( p < 0.05), total omega-3 fatty acids and LDL cholesterol ( p < 0.001), total omega-3 fatty acids and triglycerides ( p < 0.01) were positively related. Similar n-3 fatty acid intakes were reported in nutritionally aware students and other university subjects.

CONCLUSIONS

The data of this study indicate gender-related differences in response to dietary fat, and widespread low compliance with n-3 fatty acid recommendations. Although the men are highly health conscious and physically active, their blood lipid levels are indicative of a risk of cardiovascular disease. In addition to enhanced nutritional education to increase seafood intakes in this age group of men and women, customised dietary and lifestyle advice may be required in the men.

Resting energy expenditure and adiposity accretion among children with Down syndrome: a 3-year prospective study

Background

Children with Down syndrome (DS) have a higher prevalence of obesity than other children. Whether this increased risk for obesity is due to a lower resting energy expenditure (REE) is controversial. Our study assessed whether 1) the REE of children with DS adjusted for fat free mass (FFM) was lower than that of sibling controls and 2) the changes in fat mass (FM) over three years were associated with FFM-adjusted baseline REE.

Methods

This study used cross-sectional and prospective cohort designs. Four annual measurement visits were conducted with 28 children with DS and 35 sibling controls aged 3–10y. REE and serum thyroxine (T4) were measured at baseline. Anthropometry, skinfold thicknesses measures, and, in a subsample, dual energy x-ray absorptiometry (DXA) were used at each visit to calculate FM.

Results

Children with DS had significantly lower REE adjusted for FFM (−78 kcal/day, 95% CI: −133 to −27, p=0.003). The difference remained significant after adjustment for FM, sex, and African ancestry (−49 kcal/day, 95% CI: −94 to −4, p=0.03). In the longitudinal analysis, the baseline REE adjusted for baseline FFM was not predictive of FM accretion over time (p=0.8).

Conclusion

Children with DS have lower REE than sibling controls, but REE was not associated with changes in FM over time. The results suggest that the lower REE of children with DS does not explain their increased risk for obesity.

Acute effect of Fatmax exercise on the metabolism in overweight and nonoverweight girls

INTRODUCTION

Acute exercise can reduce postprandial insulin concentrations and increase fat oxidation in adults, which may have important implications for insulin resistance and weight control. However, similar studies with young people or comparing overweight (OW) and nonoverweight (NO) individuals are sparse. Therefore, the acute effect of Fatmax exercise on glucose, insulin, and fat oxidation was examined in 12 OW and 15 NO girls.

METHODS

Participants completed two 2-d conditions in a counterbalanced order. On day 1, participants either expended 2.09 MJ (500 kcal) during treadmill exercise at individual Fatmax (EX) or 0.47 MJ (112 kcal) during rest (CON). On day 2, capillary blood and expired air samples were taken in the fasting state and at regular intervals for 2 h after high-glycemic-index breakfast consumption. Subsequently, blood glucose and plasma insulin concentrations were determined, and fat oxidation was estimated.

RESULTS

Blood glucose was similar between conditions in both groups (P > 0.05). Fasting plasma insulin (P = 0.047) and total area under the 2-h curve (P = 0.049) were reduced for EX compared with CON in the NO, but not OW girls (P > 0.05). Fasting fat oxidation was higher for EX than for CON in the NO girls (P = 0.036) and fat oxidation total area under the 2-h curve was higher for EX in both groups of girls (P ≤ 0.05).

CONCLUSIONS

A bout of Fatmax exercise performed ~16 h before high-glycemic-index breakfast consumption reduced fasting and postprandial insulin concentrations in NO girls and increased fat oxidation in both OW and NO girls. The higher postintervention energy and CHO intake in the OW compared with the NO girls or differences in metabolism between the two groups may have compromised potential exercise-induced reductions in insulin the OW girls.

High energy expenditure masks low physical activity in obesity

OBJECTIVE

To investigate energy expenditure in lean and obese individuals, focusing particularly on physical activity and severely obese individuals.

DESIGN

Total daily energy expenditure (TDEE) was assessed using doubly labeled water, resting metabolic rate (RMR) by indirect calorimetry, activity energy expenditure (AEE) by difference and time spent in physical activity by multisensor activity monitors.

SUBJECTS

In all, 177 lean, Class I and severely obese individuals (age 31-56 years, body mass index 20-64 kg m(-2)) were analyzed.

RESULTS

All components of energy expenditure were elevated in obese individuals. For example, TDEE was 2404±95 kcal per day in lean and 3244±48 kcal per day in Class III obese individuals. After appropriate adjustment, RMR was similar in all groups. Analysis of AEE by body weight and obesity class indicated a lower AEE in obese individuals. Confirming lower physical activity, obese individuals spent less time engaged in moderate-to-vigorous physical activity (2.7±1.3, 1.8±0.6, 2.0±1.4 and 1.2±1.0 h per day in lean, Class I, Class II and Class III individuals) and more time in sedentary behaviors.

CONCLUSIONS

There was no indication of metabolic efficiency in even the severely obese, as adjusted RMR was similar across all groups. The higher AEE observed in the obese is consistent with a higher cost of activities due to higher body weight. However, the magnitude of the higher AEE (20-25% higher in obese individuals) is lower than expected (weight approximately 100% higher in Class III individuals). Confirming a lower volume of physical activity in the obese, the total time spent in moderate-to-vigorous physical activity and average daily metabolic equivalent of task level were lower with increasing obesity. These findings demonstrate that high body weight in obese individuals leads to a high TDEE and AEE, which masks the fact that they are less physically active, which can be influenced by duration or intensity of activity, than in lean individuals.

Birth-weight and resting metabolic rate in adulthood - sex-specific differences

INTRODUCTION

Low birth-weight is associated with an increased risk of cardiovascular disease, hypertension, and the metabolic syndrome (MetS) in adulthood. Resting metabolic rate (RMR) has been suggested to be associated with the development of obesity as well as MetS and might be an indirect indicator of sympathetic activity. This study's aim was to examine the association between birth-weight and adult RMR.

METHODS

A total of 896 men and women from the Helsinki Birth Cohort Study born 1934-44, for whom a detailed set of birth records were available, underwent measurement of body composition and RMR in adulthood.

RESULTS

Among women, birth-weight adjusted for age and fat-free mass (FFM) was inversely associated with RMR (r = -0.12; P < 0.01). For men, a u-shaped relationship was observed, both independently and after adjustment for age, fat mass, and FFM (P = 0.05 for final model).

DISCUSSION

The sex-specific differences for the association between birth-weight and adult RMR might partly be explained by differences in the developmental programming of the sympathetic nervous system between men and women. The higher adjusted RMR among those with the lowest birth-weights is consistent with previous evidence of higher sympathetic drive among these individuals.

A proposed method of bias adjustment for meta-analyses of published observational studies

OBJECTIVE

Interpretation of meta-analyses of published observational studies is problematic because of numerous sources of bias. We develop bias assessment, elicitation and adjustment methods, and apply them to a systematic review of longitudinal observational studies of the relationship between objectively measured physical activity and subsequent change in adiposity in children.

METHODS

We separated internal biases that reflect study quality from external biases that reflect generalizability to a target setting. Since published results were presented in different formats, these were all converted to correlation coefficients. Biases were considered as additive or proportional on the correlation scale. Opinions about the extent of each bias in each study, together with its uncertainty, were elicited in a formal process from quantitatively trained assessors for the internal biases and subject-matter specialists for the external biases. Bias-adjusted results for each study were combined across assessors using median pooling, and results combined across studies by random-effects meta-analysis.

RESULTS

Before adjusting for bias, the pooled correlation is difficult to interpret because the studies varied substantially in quality and design, and there was considerable heterogeneity. After adjusting for both the internal and external biases, the pooled correlation provides a meaningful quantitative summary of all available evidence, and the confidence interval incorporates the elicited uncertainties about the extent of the biases. In the adjusted meta-analysis, there was no apparent heterogeneity.

CONCLUSION

This approach provides a viable method of bias adjustment for meta-analyses of observational studies, allowing the quantitative synthesis of evidence from otherwise incompatible studies. From the meta-analysis of longitudinal observational studies, we conclude that there is no evidence that physical activity is associated with gain in body fat.

Objectively measured physical activity and obesity prevention in children, adolescents and adults: a systematic review of prospective studies

This study aimed at synthesizing the prospective associations between measured physical activity (PA) and change in adiposity in children, adolescents and adults following from two previous reviews. Search terms were adapted and a systematic literature search was conducted (January 2000-September 2008) and later updated (up to October 2009), considering observational and intervention studies of weight gain that measured both PA and body composition. Sixteen observational studies (six comprising adults) and five trials (one comprising adults) were eligible. For consistency, whenever possible either baseline PA energy expenditure or accelerometer output (counts min(-1) ) and change in per cent body fat were the extracted exposure and outcome measures. Results of observational studies suggest that PA is not strongly prospectively related with adiposity: five studies on children and three on adults reported no association between baseline PA and change in adiposity, one study found a weak positive association and the other studies observed a weak negative association. Negative associations were more frequently observed in studies that analysed the association between change in the exposure and outcome. Intervention studies show generally no effect on either PA or adiposity. In conclusion, despite the well-established health benefits of PA, it may not be a key determinant of excessive gain in adiposity.

Objectively measured physical activity and fat mass in children: a bias-adjusted meta-analysis of prospective studies

BACKGROUND

Studies investigating the prevention of weight gain differ considerably in design and quality, which impedes pooling them in conventional meta-analyses, the basis for evidence-based policy making. This study is aimed at quantifying the prospective association between measured physical activity and fat mass in children, using a meta-analysis method that allows inclusion of heterogeneous studies by adjusting for differences through eliciting and incorporating expert opinion.

METHODS

Studies on prevention of weight gain using objectively measured exposure and outcome were eligible; they were adopted from a recently published systematic review. Differences in study quality and design were considered as internal and external biases and captured in checklists. Study results were converted to correlation coefficients and biases were considered either additive or proportional on this scale. The extent and uncertainty of biases in each study were elicited in a formal process by six quantitatively-trained assessors and five subject-matter specialists. Biases for each study were combined across assessors using median pooling. Results were combined across studies by random-effects meta-analysis.

RESULTS

The combined correlation of the unadjusted results from the six studies was -0.04 (95%CI: -0.22, 0.14) with considerable heterogeneity (I² = 78%), which makes it difficult to interpret the result. After bias-adjustment the pooled correlation was -0.01 (95%CI: -0.18, 0.16) with apparent study compatibility (I² = 0%).

CONCLUSION

By using this method the prospective association between physical activity and fat mass could be quantitatively synthesized; the result suggests no association. Objectively measured physical activity may not be the key determinant of unhealthy weight gain in children.

Effects of an eight-month weight-control program on body composition and lipid oxidation rate during exercise in obese children

OBJECTIVE

To investigate the effects of an 8-month multidisciplinary weight-control program, including 2 h/week of moderate physical activity, nutritional education lessons and psychological follow-up, on body composition and lipid oxidation rate during exercise in obese children.

DESIGN

Nineteen (7 boys and 12 girls) obese children, aged 8-12 yr [mean body mass index (BMI) z-score: 2.3 and fat mass: 35.8%] participated in this study. Before and at the end of the weight-control period body composition was assessed by bioelectrical impedance, lipid oxidation rate by indirect calorimetry during a graded exercise test, and time devoted to various activities and energy intake in free-living conditions by questionnaire.

RESULTS

All children completed the study, at the end of which BMI decreased significantly by mean 0.6+/-0.5 and 0.5+/-0.8 kg/m2, in boys and girls, respectively (p<0.05), and fat mass (FM) decreased by 1.7+/-2.8 and 1.4+/-1.3 kg in boys and girls, respectively (p<0.05). In addition, lipid oxidation rate during exercise increased significantly throughout the graded exercise test up to 21% at maximal lipid oxidation rate which happened at 48+/-5% of maximal oxygen uptake (VO2max), corresponding to 64+/-5% of maximal heart rate. Time spent at sedentary and very light physical activities decreased (p<0.001) to the benefit of recreational activities at home.

CONCLUSIONS

Multidisciplinary weight-control program, with moderate-intensity physical activities, induced decreases in FM without decreases in free FM, increases in VO2max, lipid oxidation rate during exercise, and time devoted to recreational activities in free-living conditions.

Ethnicity, energy expenditure and obesity: are the observed black/white differences meaningful?

PURPOSE OF REVIEW

Recent studies have suggested that black individuals have lower energy expenditure than whites. Many investigators hypothesized that this is why black women experience higher rates of obesity than white women. These findings initiated much research on race as a primary biological determinant of obesity and energy expenditure as a potential pathway. Race is a difficult construct to use in biomedical research.

RECENT FINDINGS

Recent findings have included: an explanation for the lower resting energy expenditure observed among black adults, data showing that relative resting energy expenditure may not be a significant predictor of weight change in African-origin populations, and inconsistent data on the role of activity energy expenditure as a determinant of children's weight change.

SUMMARY

The data suggest that black individuals have lower resting energy expenditure and possibly activity energy expenditure than white individuals. The lower resting energy expenditure is probably caused by a smaller mass of high metabolically active organs. It is unlikely that increased weight gain is associated with lower resting energy expenditure or activity among blacks, because no association has been found within populations. Clinically, it is important to focus on personal modifiable risk factors, e.g., energy intake and physical activity levels.