Improved walking energy efficiency might persist in presence of simulated full weight regain after multidisciplinary weight loss in adolescents with obesity: the POWELL study.

AIM: Weight loss leads to a reduction of the energy cost of walking but the respective implications of the metabolic and mechanic changes remain unknown. The present study compares the post-weight loss energy cost of walking (Cw) with and without a total reload of the induced weight reduction in adolescents with obesity. METHODS: Energy cost of walking and substrate use were evaluated during a graded walking exercise (4×6-min at 0.75, 1, 1.25, 1.5 m.s-1) before (V1) and after a 12-week intervention in 21 adolescents with obesity (11 girls; 13.8 ± 1.4 y). After weight loss, the walking exercise was randomly repeated once without weight reload (V2) and once with a loading corresponding to the total induced weight loss during the program (V2L). Body composition was assessed before and after the intervention. RESULTS: Body weight and fat mass decreased in response to the 12-week intervention (p < 0.001), while FFM did not change. The absolute gross Cw (ml.m-1) was higher on V1 compared with V2 at every speed. The absolute net Cw (ml.m-1) was higher on V1 compared to V2L at 0.75 m.s-1 (p = 0.04) and 1 m.s-1 (p = 0.02) and higher on V2L compared with V2 at 1.5 m.s-1 (p = 0.03). Net Cw (ml.m-1.kg-1) on V1 being higher than V2 (p < 0.001), and V2L higher than V2 (p = 0.006). The absolute CHO oxidation (mg.min-1) did not show any condition effect (p = 0.12) while fat utilization was higher on V1 compared to V2 and V2L (p < 0.001). Relative to body weight CHO oxidation was lower on V1 compared to V2 (p = 0.04) and V2L (p = 0.004) while relative to body weight fat oxidation was higher on V1 than V2 (p = 0.002). CONCLUSION: Adolescents with obesity might not show an entire rise back to pre-weight loss values of their metabolic cost of walking when weight gain is simulated. These new findings suggest metabolic and physiological adaptations to weight loss of the energy metabolism that remain to be clarified.

High-intensity decreasing interval training (HIDIT) increases time above 90% [Formula: see text]O2peak.

PURPOSE: Training near [Formula: see text]O2max is considered to be the most effective way to enhance [Formula: see text]O2max. High-intensity interval training (HIIT) is a well-known time-efficient training method for improving cardiorespiratory and metabolic function and [Formula: see text]O2max. While long HIIT bouts allow [Formula: see text]O2max to be achieved quickly, short HIIT bouts improve time to exhaustion (Tlim). The aim of this study was to evaluate the time spent above 90% [Formula: see text]O2peak (T > 90% [Formula: see text]O2peak) during three different HIIT protocols. METHODS: Twelve cyclists performed three HIIT sessions. Each protocol had the same work and recovery power and ratio of work·recovery-1. The protocols consisted of long-interval HIIT (LIHIIT, 3 min work-2 min recovery), short-interval HIIT (SIHIIT, 30 s work-20 s recovery), and high-intensity decreasing interval training (HIDIT, work from 3 min to 30 s and recovery from 2 min to 20 s). T > 90% [Formula: see text]O2peak, Tlim, blood lactate [La], and rate of perceived exertion (RPE) were measured at Tlim. RESULTS: T > 90% [Formula: see text]O2peak was greater in HIDIT (312 ± 207 s) than in SIHIIT (182 ± 225 s; P = 0.036) or LIHIIT (179 ± 145 s; P = 0.027). Tlim was not significantly different (P > 0.05) between HIDIT (798 ± 185 s), SIHIIT (714 ± 265 s), and LIHIIT (664 ± 282). At Tlim, no differences in [La] and RPE were found between protocols (P > 0.05). CONCLUSION: HIDIT showed the highest T > 90% [Formula: see text]O2peak, suggesting that it may be a good strategy to increase time close to [Formula: see text]O2peak, despite similar Tlim, [La], and RPE at Tlim.

Effects of high-intensity interval training on physical capacities and substrate oxidation rate in obese adolescents.

PURPOSE: To investigate the effects of a 3-week weight-management program entailing moderate energy restriction, nutritional education, psychological counseling and three different exercise training (a: low intensity, LI: 40 % V'O2max; b: high intensity, HI: 70 % V'O2max; c: high-intensity interval training, HIIT), on body composition, energy expenditure and fat oxidation rate in obese adolescents. METHODS: Thirty obese adolescents (age: 15-17 years, BMI: 37.5 kg m-2) participated in this study. Before starting (week 0, W0) and at the end of the weight-management program (week 3, W3), body composition was assessed by an impedancemeter; basal metabolic rate (BMR), energy expenditure and substrate oxidation rate were measured during exercise and post-exercise recovery by indirect calorimetry. RESULTS: At W3, body mass (BM) and fat mass (FM) decreased significantly in all groups, the decreases being significantly greater in the LI than in the HI and HIIT subgroups (BM: -8.4 ± 1.5 vs -6.3 ± 1.9 vs -4.9 ± 1.3 kg and FM: -4.2 ± 1.9 vs -2.8 ± 1.2 vs -2.3 ± 1.4 kg, p < 0.05, respectively). V'O2peak, expressed in relative values, changed significantly only in the HI and HIIT groups by 0.009 ± 0.005 and 0.007 ± 0.004 L kg FFM-1 min-1 (p < 0.05). Furthermore, the HI and HIIT subgroups exhibited a greater absolute rate of fat oxidation between 50 and 70 % V'O2peak at W3. No significant changes were observed at W3 in BMR, energy expenditure during exercise and post-exercise recovery. CONCLUSION: A 3-week weight-management program induced a greater decrease in BM and FM in the LI than in the HI and HIIT subgroups, and greater increase in V'O2peak and fat oxidation rate in the HI and HIIT than in the LI subgroup.

Prediction of basal metabolic rate in patients with Prader-Willi syndrome.

BACKGROUND/OBJECTIVES: The objective of this study was to develop new equations for predicting basal metabolic rate (BMR) in Prader-Willi syndrome (PWS) subjects and to compare their accuracy with commonly used equations developed by Lazzer (2007), Livingston (2005), Huang (2004), Nelson (1992), Mifflin (1990), Owen (1987), WHO (1985), Bernstein (1983) and Harris-Benedict (1919), using the Bland-Altman method. SUBJECTS/METHODS: BMR was measured by indirect calorimetry and fat-free mass (FFM) and fat mass (FM) by a tetrapolar impedancemeter in 80 Caucasian PWS patients (mean body mass index: 39.1 kg/m(2); 17-50 years). Equations were derived by stepwise multiple regression analysis using a calibration group (n:50) and tested against the validation group (n:30). RESULTS: Two new equations, based on anthropometric (BMR=body mass × 0.052+sex × 0.778-age × 0.033+2.839 (R(2)adj=0.61, s.e.=0.89 MJ per day)) or body composition (BMR=FFMx0.074+FMx0.042+sexx0.636-agex0.037+2.515 (R(2)adj=0.69, s.e.=0.82 MJ per day)), were generated. Predicted BMR (PBMR) was not significantly different from the measured BMR (<3.3%), and was accurate in 59% and 62% of patients, respectively. Nevertheless, significant magnitude bias was found for both equations (P<0.001, R(2)=0.36). The Owen (1987), Mifflin (1990), Huang (2004) and Lazzer (2007) equations showed mean differences <5% and PBMR was accurate in ~50% of patients. The Livingston (2005), WHO (1985) and Harris-Benedict (1919) equations showed a PBMR overestimation >7% and were accurate in <50% of patients. The Nelson (1992) and Bernstein (1983) equations showed a greater PBMR underestimation in >60% of subjects. CONCLUSIONS: The new prediction equations showed significantly higher accuracy compared with equations tested, with exception of Lazzer (2007) and Livingston (2005) equations, and result in lower mean differences and lower limits of agreement compared with the equations tested.

Prediction of basal metabolic rate in obese children and adolescents considering pubertal stages and anthropometric characteristics or body composition.

BACKGROUND/OBJECTIVES: To develop and crossvalidate new equations for predicting basal metabolic rate (BMR) in obese children and adolescents in relation to pubertal stages, anthropometric characteristics or body composition. SUBJECTS/METHODS: A total of 1696 obese Caucasian children and adolescents (mean body mass index z-score: 3.5±0.8) participated in this study. BMR was determined by indirect calorimetry and fat-free mass (FFM) and fat mass (FM) by bioelectrical impedance analysis. Equations were derived by stepwise multiple regression analysis using a calibration cohort of 848 subjects, and the equations were crossvalidated with a Bland and Altman method in the remaining 848 subjects. RESULTS: Two new specific equations based on gender (1: males; 0: females), pubertal stages (from 1 to 5, assessed according Marshall & Tanner methods) and body weight (BW, kg), stature (m) or body composition (kg) were generated as follows: (1) BMR=(BW × 0.044)+(stature × 2.836)-(pubertal stage × 0.148)+(gender × 0.781)-0.551 (adjusted coefficient of determination (R(2)adj)= 0.69 and root mean squared error (RMSE)=0.954 MJ); (2) BMR=(FFM × 0.082)+(FM × 0.037)-(pubertal stage × 0.125)+(gender × 0.706)+2.528 (R(2)adj= 0.70 and RMSE=0.943 MJ). In the crossvalidation group, mean-predicted BMR was not significantly different from the mean-measured BMR (MBMR) for all children and adolescents, as well as for boys and girls (difference<2 %), and the limits of agreement (±2 s.d.) were +1.95 and -1.98 MJ/d, (P=NS). BMR was predicted accurately (90-110% of MBMR) in 67% of subjects. CONCLUSION: The new prediction equations considering the pubertal stages allow an accurate and more appropriate (vs equations using chronological age) estimation of BMR in obese children and adolescents.

One leg lateral jumps - a new test for team players evaluation.

AIM: We assessed the subject's capacity to accelerate himself laterally in monopodalic support, a crucial ability in several team sports, on 22 athletes, during series of 10 subsequent jumps, between two force platforms at predetermined distance. METHODS: Vertical and horizontal accelerations of the Centre of Mass (CM), contact and flight times were measured by means of force platforms and the Optojump-System®. Individual mean horizontal and vertical powers and their sum (total power) ranged between 7 and 14.5 W/kg. "Push angle", i.e., the angle with the horizontal along which the vectorial sum of all forces is aligned, was calculated from the ratio between vertical and horizontal accelerations: it varied between 38.7 and 49.4 deg and was taken to express the subject technical ability. RESULTS: The horizontal acceleration of CM, indirectly estimated as a function of subject's mass, contact and flight times, was essentially equal to that obtained from force platforms data. Since the vertical displacement can be easily obtained from flight and contact times, this allowed us to assess the Push angle from Optojump data only. CONCLUSIONS: The power developed during a standard vertical jump was rather highly correlated with that developed during the lateral jumps for right (R=0.80, N.=12) and left limb (R=0.72, N.=12), but not with the push angle for right (R=0.31, N.=12) and left limb (R=-0.43, N.=12). Hence standard tests cannot be utilised to assess technical ability. Lateral jumps test allows the coach to evaluate separately maximal muscular power and technical ability of the athlete, thus appropriately directing the training program: the optimum, for a team-sport player being high power and low push-angle, that is: being "powerful" and "efficient".

Effects of low- and high-intensity exercise training on body composition and substrate metabolism in obese adolescents.

The objective was to investigate the effects of a 3- week weight-management program including moderate energy restriction and exercise training at 2 intensities [low intensity (LI): 40% and high intensity (HI): 70% maximal oxygen uptake (V'O(2)max)] on body composition, energy expenditure, and fat oxidation rate in severely obese adolescents. Twenty obese adolescents, aged 15-17 yr (body mass index: 37.5 kg/m(2); 38.2% fat mass) participated in this study. Before starting (week 0, W0) and at the end of the weight-management period (week 3,W3), body composition was assessed by a multifrequency tetrapolar impedancemeter; basal metabolic rate (BMR), energy expenditure, and substrate oxidation rate during exercise and post-exercise recovery by indirect calorimetry. At W3, body mass and fat mass decreased significantly (p<0.005) in all groups, and the decreases were significantly greater in the LI than in the HI group (-8.1±1.6 vs -5.9±1.6 kg and -4.2±1.9 vs -2.3±1.7 kg, p<0.05, respectively). Predicted V'O(2)max, expressed in relative values, changed significantly only in the HI group by +0.010±0.006 l/(kg fat-free mass × min) (p=0.010). By contrast, no significant changes were observed at W3 in BMR, energy expenditure, and substrate oxidation rate during exercise and post-exercise recovery. In conclusion, LI (40% of V'O(2)max) physical activity favors fat oxidation and it seems advisable to encourage obese adolescents to perform LI physical activity which is more feasible and acceptable than intense exercise.

Energy expenditure and dietary intake of athletes during an ultraendurance event developed by hiking, cycling and mountain climbing.

AIM: To investigate exercise intensity, energy expenditure and energy balance of athletes during an ultraendurance event (UE) consisting in hiking, cycling and mountain climbing. METHODS: Four athletes participated in this study. Maximal oxygen uptake (VO2max) and "VO2-heart rate" relationships during cycling and walking were determined by indirect calorimetry during two graded exercise tests. Body mass and body fat mass were measured before and after the UE. During the UE, heart rate (HR), diet intake, gastrointestinal disturbances and route characteristics were monitored. RESULTS: UE duration was 19 h29 min over a distance of 108 km, with 6768 meters of altitude difference. Body mass and percent of body fat mass tended to decrease after UE (-3.2% and -8.9%, respectively). During the locomotion phases, mean exercise intensity was 50.8±10.4% of VO2max and 65.8±7.6% of HRmax. Energy expenditure amounted to 51.0±3.4 MJ. Energy supplied from diet and body fat mass oxidation was 20.4±10.7 MJ and 17.3±2.4 MJ, respectively. During the UE, athletes did not suffer of any gastrointestinal disorder. CONCLUSION: Mean exercise intensity corresponded to 51% VO2max: it was independent from the locomotion type, and it can be considered an adequate intensity for UEs with similar characteristics. Although athletes successfully completed the UE, the self regulation of energy intake led athletes to a negative energy balance. Estimation of energy expenditure prior the begin of UEs would allow athletes to better plan the diet energy intake.

Metabolic responses to submaximal treadmill walking and cycle ergometer pedalling in obese adolescents.

Physical activity is essential in obesity management because of the impact of exercise-related energy expenditure (EE) and fat oxidation (Fox) rate on a daily balance, but the specific physiological effects of different exercise modalities are scarcely known in obese individuals. The objective of the study was to compare the metabolic responses to treadmill (TM) and cycle ergometer (CE) exercise in obese adolescents. Gas exchange, heart rate (HR), blood lactate (LA) concentration, EE and Fox were determined at different intensity levels (up to about 85% of maximal oxygen uptake) during TM and CE in 14 pubertal (Tanner stage: >3) obese (BMI SDS: 2.15-3.86) male adolescents (age: 13-18 years). At comparable HR, oxygen uptake, EE and Fox were higher, and LA lower, during TM than CE (P<0.05-0.001), suggesting that cycling imposes a metabolic involvement at the level of the single active muscles greater than walking. Therefore, due to different physiological responses to TM and CE, walking was more convenient than cycling in obese adolescents, permitting to attain the same EE at lower HR, with lower blood LA concentration and with greater Fox. These conclusions seem clinically relevant when using exercise as a part of multidisciplinary treatment for juvenile obesity and amelioration of related metabolic disturbances.

Physical activity ratios for various commonly performed sedentary and physical activities in obese adolescents.

The physical activity ratio (PAR) values are commonly used to convert subjects' physical activity recalls into estimates of daily energy expenditure (DEE). A PAR is defined as the ratio between energy expenditure corresponding to a sedentary or a physical activity (kJ/min) and basal metabolic rate [(BMR) kJ/min]. The objective of the present study was to determine the PAR for different sedentary and physical activities in obese adolescents. Thirty-three obese adolescents [mean body mass index: 35.1 kg/m2; 40.3 % fat mass] aged 11 to 17 yr participated in this study. BMR was assessed by indirect calorimetry after an overnight fast by means of an open-circuit, indirect computerised calorimetry with a rigid, transparent, ventilated canopy. Energy expenditures corresponding to various sedentary and physical activities in free-living conditions were determined using a portable metabolic unit, and body composition by bioelectrical impedance analysis (BIA). The PAR of each activity was obtained by dividing the assessed energy expenditure by BMR. In this study, the PAR of various sedentary and physical activities did not vary significantly with sex, age, and body mass. Thus, the data for boys and girls were combined and the PAR for 27 sedentary and physical activities were determined. The PAR values can be applied to determine the mean DEE (kJ) using the specific equation considering BMR (kJ/min), PAR, and duration (min) of each activity performed by the subject during the 24 h. This information will be useful to health-care professionals because estimation of DEE in obese adolescents is necessary in order to prescribe an adequate dietary therapy to induce a desired level of energy deficit.

Prevalence and risk factors of metabolic syndrome in Brazilian and Italian obese adolescents: a comparison study.

BACKGROUND: Metabolic syndrome (MS) prevalence between different populations in obese adolescents is scanty to date. OBJECTIVE: To compare the MS prevalence and related risk factors in Brazilian and Italian obese adolescents. METHODS: A total of 509 adolescents (110 Brazilian, 399 Italian), aged 15-19 years. Anthropometric characteristics, triglycerides (TG), total, low-density lipoprotein (LDL)-, high-density lipoprotein (HDL)-cholesterol, fasting plasma glucose (FPG), insulin, homeostasis model assessment of insulin resistance (HOMA-IR) and blood pressure were measured. RESULTS: Age, body mass index (BMI) and BMI z-score were not significantly different between the two subgroups. BMI z-score, TG, FPG, HOMA-IR and systolic blood pressure (SBP) were significantly higher in boys than in girls both in Brazilian and Italian adolescents, while HDL-cholesterol levels were lower in boys than in girls. No significant differences were observed in BMI, LDL and total-cholesterol and DBP in two genders and groups. Insulin, FPG, HOMA-IR and TG were significantly higher, while LDL-cholesterol and SBP were significantly lower in Brazilian than in Italian subjects, both in males and females. HDL and total-cholesterol and diastolic blood pressure (DBP) were not significantly different between the two subgroups and genders. MS prevalence was higher in Brazilian than in Italian obese boys (34.8 vs. 23.6%, p < 0.001) and girls (15.6 vs. 12.5%, p < 0.01). The most frequently altered parameter was HOMA-IR both in subjects with MS (100% in Brazilian and 81.8% in Italian) and without MS (42.9% and 11.7%). CONCLUSION: Metabolic syndrome represents a worldwide emerging health problem in different ethnical populations, the alterations of the risk factors related to MS (different in their prevalence between different subgroups) being strictly linked to the degree of obesity.

The interplay between propelling efficiency, hydrodynamic position and energy cost of front crawl in 8 to 19-year-old swimmers.

The aim of this study was to investigate the interplay between the arm stroke efficiency (an index of propelling efficiency, eta (P)) and the static and dynamic position in water (indexes of hydrodynamic resistance, W (d)) in determining the energy cost of front crawl (C) during a swimmer's growth. These three parameters are indeed related by the following equation: C=W(d)/(eta(P).eta(o)) where eta (o) is the overall efficiency of swimming. The experiments were carried out on 72 swimmers (38 M and 34 F; 8-19 years) who were asked to swim at 1 m s(-1). The static position in water was assessed by measuring the underwater torque (T'); the dynamic position in water by measuring the projected frontal area (A (eff)). The ratio between the average values of the eldest to youngest class of age was 3.84 and 2.27 for T', 2.13 and 1.68 for A (eff), and 1.13 and 1.24 for eta (P) (in M and F, respectively). The increase in T' and in A (eff) was larger than the increase in efficiency suggesting that, in this age range, C should increase, the more so in M than F. Indeed, C increased by 1.58 in male and 1.17 in female swimmers. Based on the values of C and eta (P) (and assuming a constant value of eta (o)) it is possible to estimate that, in this age range, W (d) increases by about 1.97 in male and 1.32 in female swimmers, an increase which is proportional to the observed increase in A (eff).

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.

Prediction of resting energy expenditure in severely obese Italian males.

The objectives of the present study were to develop and cross-validate new equations for predicting resting energy expenditure (PREE) in severely obese Italian males, and to compare their accuracy with those of the Harris-Benedict, WHO/ FAO/UNU, Huang, Owen, Mifflin, Livingston, Nelson, Bernstein, and Cunnimgham equations in order to predict resting energy expenditure (REE), using the Bland-Altman method. One hundred and sixty-four severely obese males [mean body mass index (BMI): 45.4 kg/m2; 50.2% fat mass), aged 20 to 65 yr participated in this study. REE was measured by indirect calorimetry and body composition by bioelectrical analysis. Equations were derived by stepwise multiple regression analysis using a calibration group and tested against the validation group. Two new specific equations, based on anthropometric [REE=Weight x 0.048 + Height x 4.655 - age x 0.020 - 3.605 (R2=0.68, SE=1.14 MJ/d)] or body composition parameters [REE=fat free mass (FFM) x 0.081 + fat mass (FM) x 0.049 - age x 0.019 - 2.194 (R2=0.65, SE=1.15 MJ/d)], were generated. Mean PREE were not different from the mean measured REE (MREE) (<1%, p<0.001), REE being predicted accurately (95-105% of MREE) in 66 and 62% of subjects, respectively. The Harris-Benedict, WHO/FAO/UNU, Huang and Owen equations showed mean differences lower than 5% and PREE was accurate in less than 30% of subjects. The Mifflin, Livingston, and Nelson equations showed a mean PREE underestimation >7% (p<0.001) and PREE was accurate in less than 25% of subjects. The Bernstein and Cunningham equations showed a greater PREE underestimation (>22%, p<0.001) in more than 85% of subjects. The new prediction equations allow an accurate estimation of REE in groups of severely obese males and result in lower mean differences and lower limits of agreement between PREE and MREE than the commonly used equations.

Comparison of predictive equations for resting energy expenditure in severely obese Caucasian children and adolescents.

The objective of the present study was to compare resting energy expenditure (REE) calculated by different predictive equations (McDuffie, Derumeaux, Tverskaya, Schofield, FAO/WHO/ UNU, Harris-Benedict and Lazzer-Sartorio) to REE measured in severely obese Caucasian children and adolescents. Two hundred and eighty-seven obese children and adolescents (121 males, 166 females, mean age: 14.5 yr, mean body mass index (BMI) z-score: 3.3) participated in this study. REE was measured (MREE) by indirect calorimetry and body composition by bioelectrical impedance analysis. The FAO/WHO/UNU equations showed the lowest mean difference between predicted resting energy expenditure (PREE) and MREE (+0.2%, p=ns), but the higher SD (+/-1.16 MJ) and the PREE were accurate in 26% of subjects. The Tverskaya, Derumeaux and Harris-Benedict equations significantly underestimated REE in all children and adolescents (-7.6, -4.1, and -2.4%, respectively, p<0.05), while the Schofield and McDuffie equations overestimated REE (+2.5, +5 and 25%, respectively, p<0.05). By contrast, the Lazzer-Sartorio equations showed the greater agreement and accuracy (in 55% of subjects) between mean PREEs and MREE for all children and adolescents, as well as for boys and girls (+1.6%, p=ns). In conclusion, Lazzer-Sartorio equations showed an accurate estimation of REE in groups of severely obese children and adolescents, resulting in lower mean differences and SD and higher accuracy between PREE and MREE than the other equations considered in this study.

Prediction of resting energy expenditure in severely obese Italian women.

The aims of the present study were to develop and cross-validate new equations for predicting resting energy expenditure (PREE) in severely obese Italian women, and to compare their accuracy with those of the Harris-Benedict, Bernstein, WHO/FAO/UNU, Owen, Mifflin, Nelson, Siervo, Huang and Livingston equations to predict REE, using the Bland-Altman method. One hundred and eighty two women [mean body mass index (BMI) 45.6 kg/m2; 56.7% fat mass (FM)], aged 19 to 60 yr participated in this study. REE was measured by indirect calorimetry and body composition by bioelectrical analysis. Equations were derived by stepwise multiple regression analysis, using a calibration group and tested against the validation group. Two new specific equations based on anthropometric REE=Weightx0.042+Heightx3.619-2.678 (R2=0.66, SE=0.56 MJ) or body composition parameters REE=FFMx0.067+FMx0.046+1.568 (R2=0.63, SE=0.58 MJ) were generated. Mean PREE were no different from the mean measured resting energy expenditure (MREE) (<1%, p>0.800) and REE was predicted accurately (95-105% of MREE) in 60% of subjects. The WHO/FAO/UNU, Harris-Benedict and Siervo equations showed mean differences <2% and PREE was accurate in <44% of subjects. The Huang, Mifflin and Livingston equations showed a mean PREE underestimation (>5.0%, p<0.001) and PREE was accurate in <38% of subjects. The Owen, Bernstein and Nelson equations showed a greater PREE underestimation (>14%, p<0.001) in >90% of subjects. The new prediction equations allow an accurate estimation of REE in groups of severely obese women and result in lower mean differences and lower limits of agreement between PREE and MREE than commonly used equations.

Relationship between percentage of VO2max and type of physical activity in obese and non-obese adolescents.

AIM: The objective of the present study was to determine oxygen uptake (VO(2)) and percentage of maximum oxygen uptake (%VO2max) in obese and non-obese adolescents during various activities in standardised conditions, and the corresponding %VO2max in free-living conditions. METHODS: Twenty-seven obese and 50 non-obese adolescents aged 12 to 16 years participated in this study. Body composition was assessed by bioelectrical impedance analysis and dual energy X-ray absorptiometry (DXA), VO2max by treadmill tests, VO2 corresponding to various activities by whole body calorimetry, and time and % VO2max corresponding to various activities in free-living conditions using the heart-rate recording method and a physical activity diary. RESULTS: VO2max (l/min) was 27.4% higher in obese than in non-obese subjects (p<0.001), but not significantly different after adjustment for fat-free mass (FFM). In the whole body calorimeters, with the same activity program, % VO2max corresponding to sleep and sedentary activities were lower in obese than in non-obese girls (-15.1% and -12.3%, p<0.05), but not significantly different between obese and non-obese boys. However, walking at 4-5-6 km/h corresponded to 47-59% and 71% of VO2max, respectively, in obese, and 34-41% and 48% of VO2max in non-obese subjects (p<0.001). In free-living conditions, moderate physical activities and sports corresponded to 52% vs 35%, and 39% vs 51% of VO2max, respectively, in obese and non-obese adolescents. CONCLUSIONS: In standardised conditions %VO2max did not correspond to the same type of physical activity in obese compared to non-obese adolescents. Consequently, % VO2max is inadequate for comparing the types of physical activities of obese and non-obese adolescents in free-living conditions.

Changes in adipocyte hormones and lipid oxidation associated with weight loss and regain in severely obese adolescents.

OBJECTIVE: To investigate changes in adipocyte hormones and lipid oxidation during and after a weight-reduction programme in severely obese adolescents. DESIGN: Longitudinal-clinical investigation including a 9-month multidisciplinary weight-reduction programme in a specialised institution with lifestyle education, moderate energy restriction and regular physical activity, followed by a 4-month period at home. SUBJECTS: A total of 26 (12 boys and 14 girls) severely obese adolescents (mean BMI: 33.9 kg/m2; 41.5% fat mass (FM)). MEASUREMENTS: Before starting (M0), at the end (M9), and 4 months after the end (M13) of the intervention blood samples were collected at fast, body composition was assessed by dual X-ray absorptiometry, and energy expenditure (EE) and substrate oxidation were assessed by whole-body indirect calorimetry over 24 h. RESULTS: At M9, adolescents had lost 19.0% body weight (BW), 41.3% FM (P<0.001), with a minor fat free mass (FFM) loss in girls (6.4%, P<0.001) but no significant FFM changes in boys. Plasma leptin concentration at M9 was 70% lower (P<0.001), whereas plasma adiponectin concentration was 26.6% higher (P<0.001). The results also suggest that after adjustment for FFM and energy balance, sleeping and sedentary activity lipid oxidation rates were higher at M9 than at M0. At M13, plasma adiponectin, insulin, glucose and LDL concentrations returned to the initial levels, and leptin to an intermediate level in the 10 adolescents who had regained BW. Adjusted lipid oxidation rate decreased in both groups of subjects but it was not correlated to any change in plasma adipocyte hormones, which rather changed in relation to FM modifications. CONCLUSION: Moderate energy restriction and regular moderate and high intensity physical activities in obese adolescents induced beneficial changes in BW and composition, lipid oxidation and blood parameters, especially adipocyte hormones.

[Which alternative method to dual-energy X-ray absorptiometry for assessing body composition in overweight and obese adolescents?]. / Quelle méthode alternative à l'absorptiométrie biphotonique (DEXA) utiliser pour évaluer la composition corporelle des adolescents en surpoids ou obèses?

CONTEXT: Professionals in charge of overweight and obese children and adolescents need a simple, reliable and precise method for assessing body composition. OBJECTIVES: To compare body composition as assessed by dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA) and the skinfold thickness (SFT) method in overweight and obese adolescents, and to establish and validate new predictive equations of body composition from BIA measurements using DXA as standard method. SUBJECTS AND METHODS: Body composition was assessed in 143 obese adolescents (Z-score = 3.2 +/- 1.4) aged 12 to 17 years by DXA, BIA (RJL System, Analycor and Analycor XF models) and SFT (Siri and Slaughter's equations). New prediction equations of fat mass (FM) as assessed by DXA were computed from BIA measurements in a calibration group, and validated in an homologous group of subjects. Results. - The Bland-Altman test showed that compared to DXA, BIA underestimated FM by 2.8 +/- 2.0 kg and 2.3 +/- 2.1 kg using the RJL System and Analycor impedancemeter, respectively (P < 0.001). With the Analycor XF model, FM was underestimated by 3.3 +/-2.6 kg in boys, and over-valued by 0.6 +/- 2.4 kg in girls. On the contrary, the predictive equation of Wabitsch et al. overvalued FM by 6.2 +/- 2.9 kg. The SFT method overvalued FM by 2.1 +/- 5.0 kg in boys and underestimated FM by 2.3 +/- 3.5 kg in girls using Slaughter et al. equation, while Siri's equation underestimated FM by 4.0 +/- 2.9 kg (P < 0.001). The alternative to the DXA method to assess FM was BIA with new prediction equations including gender, body weight, height(2)/resistance and reactance. CONCLUSION: DXA, BIA and the SFT method were not directly interchangeable. The SFT method was inadequate to assess body composition in overweight and obese adolescents. BIA and new prediction equations could be an alternative to the DXA method in overweight and obese adolescents.

[Longitudinal changes in body composition and basal metabolic rate in institutionalized or domiciled obese adolescents]. / Analyse longitudinale des variations de la composition corporelle et du métabolisme de base d'adolescents obèses pris en charge en institution ou à domicile.

UNLABELLED: The prevalence of obesity in children has increased dramatically during the past decades, and requires efficient care. OBJECTIVES: To determine changes in anthropometric parameters and basal metabolic rate (BMR) in obese adolescents during and after 2 types of weight-reduction programs. SUBJECTS AND METHODS: Twenty-six adolescents (group I, Z-score of BMI = 4.72) followed a 9-month-weight reduction program including a moderate energy restriction and regular physical activities in a specialized institution. In addition, 39 adolescents (group E, Z-score of BMI = 2.83) followed at home a 9-month-weight reduction program including medical and dietetic advices. Body composition (by impedancemetry) and BMR (by indirect calorimetry) were assessed before the beginning (M0), 4 months after (M4) and at the end (M9) of the programs, then 4 months (M13) and 16 month (M25) after the end of the weight-reduction programs. RESULTS: Twenty-two adolescents in group I and 20 adolescents in group E completed the study. At M0, age, body weight (BW), fat-free mass (FFM) and BMR of subjects of group I were higher (1.0 year, 36 %, 30 % and 23 %, respectively, P < 0.001), than those of group E. Pubertal stage and percentage of fat mass (FM) were not significantly different between the 2 groups. At M9, adolescents of group I showed significant reductions in BW and FM (-19 and -37 %, respectively, P < 0.001), but not significant differences in FFM. In addition, BMR decreased significantly between M0 and M4, both in absolute value (-6.7%, P < 0.001) and after adjustment for FFM (-5.8%, P < 0.001), and the difference was maintained until M9. Between M9 and M13, BW and Z-score of BMI were maintained in 12 adolescents, but increased (+9.7% and 14.8%, respectively, P < 0.001) in 10 adolescents. However, BMR did not change significantly in all adolescents. Between M13 and M25, BW, FM, FFM and BMR increased significantly (+13%, +34%, +6% et +5%, respectively, P < 0.001). During the 25 month period, adolescents of group E showed significant increases in BW, FFM and BMR (+8%, +14% and +10%, respectively, P < 0.001), and maintained their Z-score and FM. CONCLUSION: The reduction in BMR during the weight-reduction program at the institution could contribute to body weight regain in the post-obese adolescents if they do not maintain the lifestyle habits taught during the weight-reduction period. In other respects, Z-score was stabilized in 51% of domiciled obese adolescents.