Basal metabolism of obese adolescents: inconsistent diet and exercise effects

Efficacy of exercise for treating overweight in children and adolescents: a systematic review

BACKGROUND

Overweight prevalence among children/adolescents is increasing, while adult obesity may potentially cause a decline in life expectancy. More exercise is uniformly recommended, although treatment efficacy remains unclear.

OBJECTIVE

To determine the efficacy of exercise alone for treating overweight in children/adolescents.

DESIGN

A systematic review and meta-analysis of randomized trials published in English were completed following multiple database searches performed on December 10, 2004. Studies of isolated or adjunctive exercise/physical activity treatment in overweight/obese children or adolescents which reported any overweight outcome were included. Literature searches identified 645 papers which were manually searched, of which 45 were considered for inclusion, of which 13 papers which reported 14 studies were included (N=481 overweight boys and girls, aged approximately 12 years). Two reviewers independently identified relevant papers for potential inclusion and assessed methodological quality. Principal measures of effects included the mean difference (MD) (between treatment and control groups), the weighted MD (WMD), and the standardized MD (SMD).

RESULTS

Few studies were of robust design. The pooled SMD was -0.4 (-0.7, -0.1, P=0.006) for percent body fat, and -0.2 (-0.6, 0.1, P=0.07) for central obesity outcomes, whereas the pooled WMD was -2.7 kg (-6.1 kg, 0.8 kg, P=0.07) for body weight, all of which favored exercise. Pooled effects on body weight were significant and larger for studies of higher doses, whereas nonsignificant and smaller effects were seen for studies of lower doses of exercise (155-180 min/weeks vs 120-150 min/weeks).

CONCLUSIONS

Based on the small number of short-term randomized trials currently available, an aerobic exercise prescription of 155-180 min/weeks at moderate-to-high intensity is effective for reducing body fat in overweight children/adolescents, but effects on body weight and central obesity are inconclusive. Recommendations for future study designs are discussed.

Reducing obesity and related chronic disease risk in children and youth: a synthesis of evidence with 'best practice' recommendations

Childhood obesity is a global epidemic and rising trends in overweight and obesity are apparent in both developed and developing countries. Available estimates for the period between the 1980s and 1990s show the prevalence of overweight and obesity in children increased by a magnitude of two to five times in developed countries (e.g. from 11% to over 30% in boys in Canada), and up to almost four times in developing countries (e.g. from 4% to 14% in Brazil). The goal of this synthesis research study was to develop best practice recommendations based on a systematic approach to finding, selecting and critically appraising programmes addressing prevention and treatment of childhood obesity and related risk of chronic diseases. An international panel of experts in areas of relevance to obesity provided guidance for the study. This synthesis research encompassed a comprehensive search of medical/academic and grey literature and the Internet covering the years 1982-2003. The appraisal approach developed to identify best practice was unique, in that it considered not only methodological rigour, but also population health, immigrant health and programme development/evaluation perspectives in the assessment. Scores were generated based on pre-determined criteria with programmes scoring in the top tertile of the scoring range in any one of the four appraisal categories included for further examination. The synthesis process included identification of gaps and an analysis and summary of programme development and programme effectiveness to enable conclusions to be drawn and recommendations to be made. The results from the library database searches (13,158 hits), the Internet search and key informant surveys were reduced to a review of 982 reports of which 500 were selected for critical appraisal. In total 158 articles, representing 147 programmes, were included for further analysis. The majority of reports were included based on high appraisal scores in programme development and evaluation with limited numbers eligible based on scores in other categories of appraisal. While no single programme emerged as a model of best practice, synthesis of included programmes provided rich information on elements that represent innovative rather than best practice under particular circumstances that are dynamic (changing according to population subgroups, age, ethnicity, setting, leadership, etc.). Thus the findings of this synthesis review identifies areas for action, opportunities for programme development and research priorities to inform the development of best practice recommendations that will reduce obesity and chronic disease risk in children and youth. A lack of programming to address the particular needs of subgroups of children and youth emerged in this review. Although immigrants new to developed countries may be more vulnerable to the obesogenic environment, no programmes were identified that specifically targeted their potentially specialized needs (e.g. different food supply in a new country). Children 0-6 years of age and males represented other population subgroups where obesity prevention programmes and evidence of effectiveness were limited. These gaps are of concern because (i) the pre-school years may be a critical period for obesity prevention as indicated by the association of the adiposity rebound and obesity in later years; and (ii) although the growing prevalence of obesity affects males and females equally; males may be more vulnerable to associated health risks such as cardiovascular disease. Other gaps in knowledge identified during synthesis include a limited number of interventions in home and community settings and a lack of upstream population-based interventions. The shortage of programmes in community and home settings limits our understanding of the effectiveness of interventions in these environments, while the lack of upstream investment indicates an opportunity to develop more upstream and population-focused interventions to balance and extend the current emphasis on individual-based programmes. The evidence reviewed indicates that current programmes lead to short-term improvements in outcomes relating to obesity and chronic disease prevention with no adverse effects noted. This supports the continuation and further development of programmes currently directed at children and youth, as further evidence for best practice accumulates. In this synthesis, schools were found to be a critical setting for programming where health status indicators, such as body composition, chronic disease risk factors and fitness, can all be positively impacted. Engagement in physical activity emerged as a critical intervention in obesity prevention and reduction programmes. While many programmes in the review had the potential to integrate chronic disease prevention, few did; therefore efforts could be directed towards better integration of chronic disease prevention programmes to minimize duplication and optimize resources. Programmes require sustained long-term resources to facilitate comprehensive evaluation that will ascertain if long-term impact such as sustained normal weight is maintained. Furthermore, involving stakeholders in programme design, implementation and evaluation could be crucial to the success of interventions, helping to ensure that needs are met. A number of methodological issues related to the assessment of obesity intervention and prevention programmes were identified and offer insight into how research protocols can be enhanced to strengthen evidence for obesity interventions. Further research is required to understand the merits of the various forms in which interventions (singly and in combination) are delivered and in which circumstances they are effective. There is a critical need for the development of consistent indicators to ensure that comparisons of programme outcomes can be made to better inform best practice.

Changes in fat mass, fat-free mass and aerobic fitness in severely obese children and adolescents following a residential treatment programme

The purpose of this study was to describe changes in fat mass (FM), fat-free mass (FFM) and aerobic fitness in severely obese children and adolescents during residential treatment in the Medical Paediatric Centre Zeepreventorium. Treatment consisted of moderate dietary restriction, physical activity and psychological support. This study was a clinical observation of 20 severely obese children and adolescents (8 boys and 12 girls, aged 15.4+/-1.8 years) who completed the 10-month residential programme. Height, weight, FM, FFM and aerobic fitness was measured four times during the intervention: at baseline, 11 weeks, 24 weeks and at 33 weeks (at the end of the programme ). The mean decrease in level of overweight was 46% (P<0.001), with a mean loss of 8.9% FM (P<0.001). Submaximal performance (PWC150) improved from 123+/-35 Watt to 152+/-37 Watt (P<0.001). Maximal performance levels increased (performance time: from 14+/-2.9 min to 15.3+/-3.5 min, peak power: from 186+/-38 Watt to 205+/-45 Watt, P<0.01) without an improvement in absolute VO(2 peak).

CONCLUSION

A moderate dietary restriction in combination with physical activity and psychological support in severely obese children and adolescents is effective in decreasing body fat and improving physical performance. Further research is needed to evaluate the longer-term effects of such a programme.

Obesidade: atualização sobre sua etiologia, morbidade e tratamento

As tendências de transição nutricional ocorridas neste século direcionam para uma dieta mais ocidentalizada, a qual, aliada à diminuição progressiva da atividade física, converge para o aumento no número de casos de obesidade em todo o mundo. Isso representa aumento na morbidade e na mortalidade associadas à obesidade, já que esta é fator de risco para várias doenças como diabetes tipo II, hipertensão, doenças cardiovasculares e cálculo na vesícula biliar. A obesidade se apresenta não apenas como problema científico e de saúde pública, porém como grande indústria que envolve o desenvolvimento de fármacos, de alimentos modificados e estratégias governamentais estimulando a prática regular de atividade física e a orientação alimentar a fim de promover melhores hábitos. Assim, o conhecimento das causas e estratégias preventivas da obesidade é o objeto de estudo de pesquisadores de diferentes centros. Esse artigo tem como objetivo rever esses estudos, abordando o aumento na prevalência e incidência da obesidade, doenças relacionadas ao excesso de peso e os tratamentos para redução da gordura corporal.

Reduced short-term thermic effects of a meal in obese adolescent girls

Post-meal energy expenditure (TEM) was compared for 14 healthy obese (body fat = 45.3%, body mass index, BMI = 35.9 kg m-2) and 9 healthy nonobese (body fat = 20.7%, BMI = 17.8 kg m-2) adolescent girls. The test meal for both groups was a standard 3348.8-kJ, 0.473-1 chocolate milkshake of 15% protein (casein), 40% fat (polyunsaturated/saturated ratio = 0.05; 75 mg cholesterol) and 45% carbohydrate (lactose and sucrose). Glucose, insulin and resting energy expenditure (RMR) were measured at rest prior to meal consumption and 20, 40, 60, 90, and 120 min after the meal. Cumulative net TEM was calculated as the integrated area under the TEM curve with RMR as baseline. Reliability was assessed by retesting 4 subjects, and a placebo effect was tested by administering a flavored energy-free drink. Results indicated high reliability and no placebo effect. The meal resulted in a greater rise in insulin and glucose for the obese compared to the nonobese subjects (P < or = 0.05), and a significant TEM for both groups (P < or = 0.05). The cumulative TEM (W kg-1) was 61.9% greater for the nonobese (P < 0.01) when expressed relative to body mass, and 33.2% greater for the nonobese (P < or = 0.01) when expressed relative to the fat-free body mass. Expressed relative to the meal, the TEM was 25.5% less for the obese (P < 0.01). The data support an energy conservation hypothesis for obese female adolescents.