David Thivel

Active video games and health indicators in children and youth: a systematic review

Background Active video games (AVGs) have gained interest as a way to increase physical activity in children and youth. The effect of AVGs on acute energy expenditure (EE) has previously been reported; however, the influence of AVGs on other health-related lifestyle indicators remains unclear. Objective This systematic review aimed to explain the relationship between AVGs and nine health and behavioural indicators in the pediatric population (aged 0–17 years). Data sources Online databases (MEDLINE, EMBASE, psycINFO, SPORTDiscus and Cochrane Central Database) and personal libraries were searched and content experts were consulted for additional material. Data selection Included articles were required to have a measure of AVG and at least one relevant health or behaviour indicator: EE (both habitual and acute), adherence and appeal (i.e., participation and enjoyment), opportunity cost (both time and financial considerations, and adverse events), adiposity, cardiometabolic health, energy intake, adaptation (effects of continued play), learning and rehabilitation, and video game evolution (i.e., sustainability of AVG technology). Results 51 unique studies, represented in 52 articles were included in the review. Data were available from 1992 participants, aged 3–17 years, from 8 countries, and published from 2006–2012. Overall, AVGs are associated with acute increases in EE, but effects on habitual physical activity are not clear. Further, AVGs show promise when used for learning and rehabilitation within special populations. Evidence related to other indicators was limited and inconclusive. Conclusions Controlled studies show that AVGs acutely increase light- to moderate-intensity physical activity; however, the findings about if or how AVG lead to increases in habitual physical activity or decreases in sedentary behaviour are less clear. Although AVGs may elicit some health benefits in special populations, there is not sufficient evidence to recommend AVGs as a means of increasing daily physical activity.

Effect of android to gynoid fat ratio on insulin resistance in obese youth.

BACKGROUND Upper body fat distribution is associated with the early development of insulin resistance in obese children and adolescents. OBJECTIVE To determine if an android to gynoid fat ratio is associated with the severity of insulin resistance in obese children and adolescents, whereas peripheral subcutaneous fat may have a protective effect against insulin resistance. SETTING The pediatric department of University Hospital, Clermont-Ferrand, France. DESIGN A retrospective analysis using data from medical consultations between January 2005 and January 2007. PARTICIPANTS Data from 66 obese children and adolescents coming to the hospital for medical consultation were used in this study. MAIN OUTCOME MEASURES Subjects were stratified into tertiles of android to gynoid fat ratio determined by dual-energy x-ray absorptiometry. Insulin resistance was assessed by the homeostasis model of insulin resistance (HOMA-IR) index. RESULTS There were no differences in weight, body mass index, and body fat percentage between tertiles. Values of HOMA-IR were significantly increased in the 2 higher tertiles (mean [SD], tertile 2, 2.73 [1.41]; tertile 3, 2.89 [1.28]) compared with the lower tertile (tertile 1, 1.67 [1.24]) of android to gynoid fat ratio (P < .001). The HOMA-IR value was significantly associated with android to gynoid fat ratio (r = 0.35; P < .01). CONCLUSIONS Android fat distribution is associated with an increased insulin resistance in obese children and adolescents. An android to gynoid fat ratio based on dual-energy x-ray absorptiometry measurements is a useful and simple technique to assess distribution of body fat associated with an increased risk of insulin resistance.

The 24-h Energy Intake of Obese Adolescents Is Spontaneously Reduced after Intensive Exercise: A Randomized Controlled Trial in Calorimetric Chambers

Background Physical exercise can modify subsequent energy intake and appetite and may thus be of particular interest in terms of obesity treatment. However, it is still unclear whether an intensive bout of exercise can affect the energy consumption of obese children and adolescents. Objective To compare the impact of high vs. moderate intensity exercises on subsequent 24-h energy intake, macronutrient preferences, appetite sensations, energy expenditure and balance in obese adolescent. Design This randomized cross-over trial involves 15 obese adolescent boys who were asked to randomly complete three 24-h sessions in a metabolic chamber, each separated by at least 7 days: (1) sedentary (SED); (2) Low-Intensity Exercise (LIE) (40% maximal oxygen uptake, VO2max); (3) High-Intensity Exercise (HIE) (75%VO2max). Results Despite unchanged appetite sensations, 24-h total energy intake following HIE was 6–11% lower compared to LIE and SED (p<0.05), whereas no differences appeared between SED and LIE. Energy intake at lunch was 9.4% and 8.4% lower after HIE compared to SED and LIE, respectively (p<0.05). At dinner time, it was 20.5% and 19.7% lower after HIE compared to SED and LIE, respectively (p<0.01). 24-h energy expenditure was not significantly altered. Thus, the 24-h energy balance was significantly reduced during HIE compared to SED and LIE (p<0.01), whereas those of SED and LIE did not differ. Conclusions In obese adolescent boys, HIE has a beneficial impact on 24-h energy balance, mainly due to the spontaneous decrease in energy intake during lunch and dinner following the exercise bout. Prescribing high-intensity exercises to promote weight loss may therefore provide effective results without affecting appetite sensations and, as a result, food frustrations. Trial Registration ClinicalTrial.gov NCT01036360

Do mechanical gait parameters explain the higher metabolic cost of walking in obese adolescents

Net metabolic cost of walking normalized by body mass (C(W.BM(-1)); in J.kg(-1).m(-1)) is greater in obese than in normal-weight individuals, and biomechanical differences could be responsible for this greater net metabolic cost. We hypothesized that, in obese individuals, greater mediolateral body center of mass (COM) displacement and lower recovery of mechanical energy could induce an increase in the external mechanical work required to lift and accelerate the COM and thus in net C(W.BM(-1)). Body composition and standing metabolic rate were measured in 23 obese and 10 normal-weight adolescents. Metabolic and mechanical energy costs were assessed while walking along an outdoor track at four speeds (0.75-1.50 m/s). Three-dimensional COM accelerations were measured by means of a tri-axial accelerometer and gyroscope and integrated twice to obtain COM velocities, displacements, and fluctuations in potential and kinetic energies. Last, external mechanical work (J.kg(-1).m(-1)), mediolateral COM displacement, and the mechanical energy recovery of the inverted pendulum were calculated. Net C(W.BM(-1)) was 25% higher in obese than in normal-weight subjects on average across speeds, and net C(W.BM(-67)) (J.kg(-0.67).m(-1)) was significantly related to percent body fat (r(2) = 0.46). However, recovery of mechanical energy and the external work performed (J.kg(-1).m(-1)) were similar in the two groups. The mediolateral displacement was greater in obese subjects and significantly related to percent body fat (r(2) = 0.64). The mediolateral COM displacement, likely due to greater step width, was significantly related to net C(W.BM(-67)) (r(2) = 0.49). In conclusion, we speculate that the greater net C(W.BM(-67)) in obese subjects may be partially explained by the greater step-to-step transition costs associated with wide gait during walking.

Daily energy balance in children and adolescents. Does energy expenditure predict subsequent energy intake

Both physical and sedentary activities primarily impact energy balance through energy expenditure, but they also have important implications in term of ingestive behavior. The literature provides scarce evidence on the relationship between daily activities and subsequent nutritional adaptations in children and adolescents. Sedentary activities and physical exercise are generally considered distinctly despite the fact that they represent the whole continuum of daily activity-induced energy expenditure. This brief review paper examines the impact of daily activities (from vigorous physical activity to imposed sedentary behaviors) on acute energy intake control of lean and obese children and adolescents, and whether energy expenditure is the main predictor of subsequent energy intake in this population. After an overview of the available literature, we conclude that both acute physical activity and sedentary behaviors induce food consumption modifications in children and adolescents but also that the important discrepancy between the methodologies used does not allow any clear conclusion so far. When considering energy intake responses according to the level of energy expenditure generated by those activities, it is clear that energy expenditure is not the main predictor of food consumption in both lean and obese children and adolescents. This suggests that other characteristics of those activities may have a greater impact on calorie intake (such as intensity, duration or induced mental stress) and that energy intake may be mainly determined by non-homeostatic pathways that could override the energetic and hormonal signals.

Intensive exercise: A remedy for childhood obesity?

BACKGROUND Acute exercise can affect the energy intake regulation, which is of major interest in terms of obesity intervention and weight loss. OBJECTIVE To test the hypothesis that intensive exercise can affect the subsequent energy intake and balance in obese adolescents. DESIGN The study was conducted in 2009 and enrolled 12 obese pubertal adolescents ages 14.4±1.5 years old. Two exercise and one sedentary sessions were completed. The first exercise (EX(1)) and sedentary session (SED) were randomly conducted 1 week apart. The second exercise session (EX₂) was conducted following 6 weeks of diet modification and physical activity (3×90 min/week) to produce weight loss. Energy intake was recorded, subjective appetite sensation was evaluated using Visual Analogue Scales and energy expenditure was measured using ActiHerats during EX(1), EX₂ and SED. RESULTS Total energy intake over the awakened period was significantly reduced by 31% and 18% during the EX(1) and EX(2) sessions compared with the SED session, respectively (p<0.01). Energy balance over the awakened period was negative during EX₁, neutral during EX₂ and positive during SED. There was no significant difference in terms of subjective appetite rates between sessions during the awakened hours. CONCLUSIONS Intensive exercise favors a negative energy balance by dually affecting energy expenditure and energy intake without changes in appetite sensations, suggesting that adolescents are not at risk of food frustration.

Mechanical Work and Metabolic Cost of Walking after Weight Loss in Obese Adolescents

PURPOSE This study was performed to investigate whether changes in biomechanical parameters of walking explain the reduction in net metabolic cost after weight loss in obese adolescents. METHODS Body composition and metabolic and mechanical energy costs of walking at 1.25 m·s(-1) were assessed in 16 obese adolescents before and after a weight loss. Center of mass (COM) and foot accelerations were measured using two inertial sensors and integrated twice to determine COM and foot velocities and displacements. Potential and kinetic energy fluctuations of the COM and the external mechanical work were calculated. Lateral leg swing was calculated from foot displacements. RESULTS As expected, the decrease in net metabolic cost was greater, which would have been expected on the basis of the amount of weight loss. The smaller lateral leg swing after weight loss did not explain part of the decrease in net metabolic cost. The reduced body mass required less leg muscle work to raise and accelerate the COM as well as to support body weight. The decrease in body mass seems also associated with a lesser leg muscle work required to raise the COM because of smaller vertical motions. As a result of the inverted pendulum mechanism, the decrease in vertical motions (hence in potential energy fluctuations) was probably related to the decrease in mediolateral kinetic energy fluctuations. Moreover, the lesser amount of fat mass in the gynoid region seems related to the decrease in net metabolic cost of walking. CONCLUSIONS The reduction in net metabolic cost of walking after weight loss in weight-reduced adolescents is associated with changes in the biomechanical parameters of walking.

Modern Sedentary Behaviors Favor Energy Consumption in Children and Adolescents

With the modernization of societies, daily living, school, chores and work tasks are less energy demanding and sedentary behaviors such as television viewing and video game playing are pervasive, particularly in children and adolescents. This sedentary behavior constellation has contributed to the progression of overweight and obesity. The low energy expenditure associated to daily sedentary behaviors has been postulated as the primary mechanism to explain population weight gain; however, recent evidence reveals that many sedentary behaviors also promote overconsumption of food. The present paper summarizes the available literature about the impact of sedentary behaviors on energy intake and appetite sensations in children and adolescents. Overall, screen-based sedentary behaviors (e.g., television viewing and video game playing) stimulate food intake in children and youth, while the influence of non-screen sedentary behaviors on feeding behavior remains largely unexplored. As in adults, insufficient sleep and waked resting positions (sitting or bed rest) are associated with increased energy consumption. Because all of these activities increase energy intake in the absence of hunger, the hedonic (rewarding) component of eating behavior seems to play an important role. At present, public health recommendations focus on increasing physical activity energy expenditure and reducing sedentary time in children and youth. From an energy balance standpoint, the impact of modern sedentary behaviors on food consumption should also be considered if we want to curb childhood obesity. A better understanding of the physiological, psychological and sociological mechanisms involved in the nutritional adaptations to sedentary activities is needed to more adequately elucidate the interplay between sedentary behaviors, feeding behaviors and obesity.

Why Does Walking Economy Improve after Weight Loss in Obese Adolescents

PURPOSE This study tested the hypothesis that the increase in walking economy (i.e., decrease in net metabolic rate per kilogram) after weight loss in obese adolescents is induced by a lower metabolic rate required to support the lower body weight and maintain balance during walking. METHODS Sixteen obese adolescent boys and girls were tested before and after a weight reduction program. Body composition and oxygen uptake while standing and walking at four preset speeds (0.75, 1, 1.25, and 1.5 m·s⁻¹) and at the preferred speed were quantified. Net metabolic rate and gross metabolic cost of walking-versus-speed relationships were determined. A three-compartment model was used to distinguish the respective parts of the metabolic rate associated with standing (compartment 1), maintaining balance and supporting body weight during walking (compartment 2), and muscle contractions required to move the center of mass and limbs (compartment 3). RESULTS Standing metabolic rate per kilogram (compartment 1) significantly increased after weight loss, whereas net metabolic rate per kilogram during walking decreased by 9% on average across speeds. Consequently, the gross metabolic cost of walking per unit of distance-versus-speed relationship and hence preferred walking speeds did not change with weight loss. Compartment 2 of the model was significantly lower after weight loss, whereas compartment 3 did not change. CONCLUSIONS The model showed that the improvement in walking economy after weight loss in obese adolescents was likely related to the lower metabolic rate of the isometric muscular contractions required to support the lower body weight and maintain balance during walking. Contrastingly, the part of the total metabolic rate associated with muscle contractions required to move the center of mass and limbs did not seem to be related to the improvement in walking economy in weight-reduced individuals.

Acute Exercise and Subsequent Nutritional Adaptations

The imbalance between energy expenditure and energy intake is the main factor accounting for the progression of obesity. For many years, physical activity has been part of weight-loss programmes to increase energy expenditure. It is now recognized that exercise can also affect appetite and energy consumption. In the context of seeking new obesity treatments, it is of major interest to clarify the impact of physical exercise on energy intake. Many reviews on this topic have been published regarding both lean and overweight adults, and this review focuses on the relationships between acute exercise and the short-term regulation of energy intake in lean and overweight or obese youths. The current literature provides very few data regarding the impact of exercise on subsequent energy intake and perceived and measured appetite in children and adolescents, mainly because of methodological difficulties in the assessment of both energy intake and expenditure. It has been long suggested that energy intake was regulated after exercise in order to compensate for the exercise-induced energy expenditure and then preserve energy balance. This overview underlines that the energy expended during exercise is not the main parameter that influences subsequent energy intake in both lean and overweight/obese children and adolescents, and that factors such as the duration or intensity of exercise may have larger impact. The effects of acute exercise on the following nutritional adaptations (energy intake and appetite feelings) remain inconclusive in lean youths, mainly due to the lack of data and the disparity of the methodologies used. Studies in overweight or obese children and adolescents are confronted with the same difficulties, and the few available data suggest that intensive exercise (>70% maximal oxygen consumption) can induce a reduction in daily energy balance, as a result of its anorexigenic effect in obese adolescents. However, further studies are needed to clarify the impact of acute exercise on subsequent nutritional adaptations and appetite-related hormones in children and adolescents, and to investigate the effect of chronic exercise programmes.