Tim Gill

Obesity prevention: a proposed framework for translating evidence into action

Obesity as a major public health and economic problem has risen to the top of policy and programme agendas in many countries, with prevention of childhood obesity providing a particularly compelling mandate for action. There is widespread agreement that action is needed urgently, that it should be comprehensive and sustained, and that it should be evidence‐based. While policy and programme funding decisions are inevitably subject to a variety of historical, social, and political influences, a framework for defining their evidence base is needed. This paper describes the development of an evidence‐based, decision‐making framework that is particularly relevant to obesity prevention. Building upon existing work within the fields of public health and health promotion, the Prevention Group of the International Obesity Task Force (IOTF) developed a set of key issues and evidence requirements for obesity prevention. These were presented and discussed at an IOTF workshop in April 2004 and were then further developed into a practical framework. The framework is defined by five key policy and programme issues that form the basis of the framework. These are: (i) building a case for action on obesity; (ii) identifying contributing factors and points of intervention; (iii) defining the opportunities for action; (iv)evaluating potential interventions; and (v) selecting a portfolio of specific policies, programmes, and actions. Each issue has a different set of evidence requirements and analytical outputs to support policy and programme decision‐making. Issue 4 was identified as currently the most problematic because of the relative lack of efficacy and effectiveness studies. Compared with clinical decision‐making where the evidence base is dominated by randomized controlled trials with high internal validity, the evidence base for obesity prevention needs many different types of evidence and often needs the informed opinions of stakeholders to ensure external validity and contextual relevance.

A synthesis of existing systematic reviews and meta-analyses of school-based behavioural interventions for controlling and preventing obesity

Schools are an attractive and popular setting for implementing interventions for children. There is a growing body of empirical research exploring the efficacy of school‐based obesity prevention programs. While there have been several reviews on the topic, findings remain mixed. To examine the quality of evidence and compare the findings from existing systematic reviews and meta‐analyses of school‐based programs in the prevention and control of childhood obesity. This paper systematically appraises the methodology and conclusions of literature reviews examining the effectiveness of school‐based obesity interventions published in English in peer‐reviewed journals between January 1990 and October 2010. Eight reviews were examined, three meta‐analyses and five systematic reviews. All of the reviews recognized that studies were heterogeneous in design, participants, intervention and outcomes. Intervention components in the school setting associated with a significant reduction of weight in children included long‐term interventions with combined diet and physical activity and a family component. Several reviews also found gender differences in response to interventions. Of the eight reviews, five were deemed of high quality and yet limited evidence was found on which to base recommendations. As no single intervention will fit all schools and populations, further high‐quality research needs to focus on identifying specific program characteristics predictive of success.

Age, period and birth cohort effects on prevalence of overweight and obesity in Australian adults from 1990 to 2000

Objective:To assess the individual contributions of age, period and birth cohort to prevalence of overweight and obesity in the Australian population during 1990 to 2000.Design:Age-period-cohort Poisson regression modelling of data from National Health Surveys conducted in Australia in 1990, 1995 and 2000.Subjects:Adults aged 20 years and over. Weightings were applied to account for differences in sampling and participation rates so that the sample is representative of the entire Australian adult population.Methods:Twelve age groups, based on 5-year intervals from 20 to 24 years to greater than 75 years, three survey periods and 14 cohorts, also based on 5-year intervals from pre-1915 up to 1976–1980, were used in the analysis. The data were age-standardized to the 2000 population and body mass index (BMI) was calculated. Log-linear models, for the prevalence rates of overall overweight (BMI ⩾25) and of obesity (BMI ⩾30) were fitted to the data.Results:Age (P<0.001), period (P<0.001) and cohort (P=0.002) all showed significant independent effects on prevalence of overall overweight in the Australian population such that prevalence rises with increasing age, recency of period and cohorts born since 1960. Age (P<0.001) and period (P<0.001) demonstrated strong effects on prevalence of obesity but birth cohort (P=0.07) was not significant. The effects were similar for men and women except that the overall effect of birth cohort on overall overweight was significant in women (P<0.05) but not men (P=0.09).Conclusion:The prevalence of overweight and obesity in Australian adults continued to rise during the 1990s. The obesogenic environment seems to have worsened and more recently born cohorts may be at increased risk of overweight.

Dairy consumption and overweight and obesity: a systematic review of prospective cohort studies

A comprehensive literature search was undertaken to examine the relationship between dairy consumption and overweight/obesity in prospective cohort studies. A literature search from 1980 through to April 2010 was conducted. Nineteen cohort studies met all the inclusion criteria and were included in the systematic review. Of the 19 cohort studies, 10 were among children and adolescents (aged 2 to 14 years, n = 53 to 12 829, follow‐up 8 months to 10 years) and nine among adults (aged 18 to 75 years, n = 248 to 42 696, follow‐up 2 years to 12 years). A range of dairy food exposure measures were used. Eight studies (three out of 10 studies involving children and five out of nine studies involving adults) showed a protective association against increasing weight gain (measured in various ways); one reported a significant protective association only among men who were initially overweight; seven reported no effect; one reported an increased risk (among children), and two reported both a decreased and increased risk, depending on the dairy food type. The evidence from prospective cohort studies for a protective effect of dairy consumption on risk of overweight and obesity is suggestive but not consistent, making firm conclusions difficult.

Consumption of 'extra' foods by Australian children: types, quantities and contribution to energy and nutrient intakes

Objective:To measure the types and quantities of energy-dense, nutrient-poor ‘extra’ foods consumed by Australian children and adolescents and their contribution to total energy and nutrient intakes.Design, setting and subjects:We used data from 3007 children, aged 2–18 years, who participated in the nationally representative 1995 National Nutrition Survey. Intake was determined by 24-h recall and ‘extra’ foods were defined using principles outlined in the Australian Guide to Healthy Eating (AGHE) and by applying cut points for maximum amounts of fat and sugar within each food category.Results:All children (99.8%) consumed at least one ‘extra’ food and the most commonly consumed were margarine, sugar-sweetened soft drinks, cordials and sugar. ‘Extra’ foods contributed 41% of daily energy intake. Those foods contributing most to energy intake were fried potatoes (4.2%), sugar-sweetened soft drinks (3.3%), ice cream/ice confection (3.1%) and cordials (2.7%). Age and sex were important determinants of ‘extra’ food intake, with males and older children generally consuming more and different types of, ‘extra’ foods than females and younger children. ‘Extra’ foods contributed 19% protein, 47% total fat, 47% saturated fat, 54% sugar, and approximately 20–25% of selected micronutrients to the diet. Calcium and zinc intakes from core foods were below 70% of the recommended dietary intakes for adolescent girls.Conclusions:‘Extra’ foods are over-consumed at two to four times the recommended limits and contribute excessively to the energy, fat and sugar intakes of Australian children, while providing relatively few micronutrients. This is of concern in terms of childrens weight and nutrient status.Sponsorship:DR was on placement at NSW Centre for Public Health Nutrition as part of the NSW Health Biostatistical Officer Trainee Program.

Plasma leptin is associated with insulin resistance independent of age, body mass index, fat mass, lipids, and pubertal development in nondiabetic adolescents.

OBJECTIVE: The rising epidemic worldwide in overweight and obese children requires urgent attention. Leptin has been found to be associated with body weight control and possibly affects insulin sensitivity. Since insulin resistance is associated with obesity in adults and possibly in adolescents, we set out to investigate the association of plasma leptin level with various anthropometric indices, body fat mass (FM), lipids, and insulin resistance (IR) index in nondiabetic adolescents.DESIGN: A cross-sectional study from three high schools in Taipei City in Taiwan.SUBJECTS: A total of 402 nondiabetic subjects (162 boys and 240 girls; age range, 10–19 y; mean age, 15.8±1.9 y, and mean body mass index (BMI), 24.8±4.6 kg/m2) were recruited.MEASUREMENTS: The fasting plasma leptin, plasma glucose, insulin, lipids, and anthropometric indices including height, weight, waist (WC) and hip circumferences, and waist-to-hip ratio (WHR) were examined. Total body FM and percentage body fat (FM%) were obtained from dual-energy X-ray absorptiometry. The homeostasis model was applied to estimate the degree of IR.RESULTS: The plasma leptin levels were significantly higher in girls (17.45±10.13 ng/ml) than boys (8.81±6.71 ng/ml, P<0.001). The plasma leptin levels were positively correlated to BMI, WC, WHR, FM, FM%, and triglycerides (TG). The IR index was positively correlated to BMI, WC, WHR, FM, FM%, TG, and leptin. Using the multivariate linear regression models, we found that plasma leptin remains significantly associated with IR index even after adjusting for age, gender, BMI, FM, WC, Tanner stage, and TG.CONCLUSION: Plasma leptin was associated with IR index independent of age, gender, BMI, FM, WC, Tanner stage, and TG. Plasma leptin levels in adolescents could be a predictor for the development of the metabolic syndrome disorders and cardiovascular diseases.

Consumption of ‘extra’ foods by Australian adults: types, quantities and contribution to energy and nutrient intakes

Objectives:To identify the types and quantities of ‘extra’ foods, or energy-dense, nutrient-poor foods, consumed by Australian adults, and assess their contribution to total energy and nutrient intakes.Subject/Methods:We used 24-h recall data from 10 851 adults, aged 19 years and over, who participated in the nationally representative 1995 National Nutrition Survey. ‘Extra’ foods were defined using principles outlined in the Australian Guide to Healthy Eating and by applying cut points for maximum amounts of fat and sugar within each food category.Results:‘Extra’ foods contributed to 36% of daily energy intake with the highest contributors being fried potatoes (2.8%), margarine (2.6%), cakes and muffins (2.5%), beer (2.4%), sugar-sweetened soft drinks (2.4%), and meat pies (2.2%). Both age and sex were important determinants of ‘extra’ foods intake; younger adults were more likely to consume sugar-sweetened soft drinks, fried potatoes, meat pies and savoury pastries, pizza, crisps, lollies and chocolate; whereas older adults were more likely to consume sweet and savoury biscuits, cakes and muffins, margarine and butter. In all age groups, ‘extra’ foods contributed more to energy intake for men than women. Overall, ‘extra’ foods contributed 16% protein, 41% total fat, 41% saturated fat, 47% sugar and approximately 20% of selected micronutrients to the diet.Conclusions:‘Extra’ foods contribute excessively to the energy, fat and sugar intakes of Australian adults, while providing relatively few micronutrients. This is of concern for the increasing risk of overweight and chronic disease and poor micronutrient status.

Higher regular fat dairy consumption is associated with lower incidence of metabolic syndrome but not type 2 diabetes

BACKGROUND AND AIMS Limited evidence suggests habitual dairy consumption to be protective against metabolic syndrome (MetSyn) and type 2 diabetes among older adults. We assessed the association of baseline consumption of dairy products with the incidence of MetSyn and type 2 diabetes among a cohort of Australian adults aged 49 years and over. METHODS AND RESULTS A validated 145-item semi-quantitative food frequency questionnaire was used to assess food and nutrient intake at baseline. Ten-year incidence of MetSyn and type 2 diabetes were obtained from 1807 and 1824 subjects respectively. Odds ratios (OR) were calculated by discrete time logistic regression modelling. Compared with subjects in the lowest intake quartile of regular fat dairy products, those in the highest quartile had a 59% lower risk of MetSyn (multivariate adjusted OR: 0.41; 95% CI: 0.23-0.71; p(trend) = 0.004), after adjustment for risk factors. Among obese subjects, an association between a high intake of regular fat dairy foods and reduced risk of type 2 diabetes was also found (age and sex adjusted OR 0.37; 95% CI: 0.16-0.88; p(trend) = 0.030), but the association did not persist after adjustment for additional confounders. There was no association between total dairy consumption and risk of MetSyn or type 2 diabetes. CONCLUSIONS We found an inverse association between regular fat dairy consumption and risk of MetSyn among Australian older adults. Further studies are warranted to examine the association between weight status, dairy consumption and risk of type 2 diabetes.

A systematic methodology to estimate added sugar content of foods

Background/objectives:The effect of added sugar on health is a topical area of research. However, there is currently no analytical or other method to easily distinguish between added sugars and naturally occurring sugars in foods. This study aimed to develop a systematic methodology to estimate added sugar values on the basis of analytical data and ingredients of foods.Subjects/methods:A 10-step, stepwise protocol was developed, starting with objective measures (six steps) and followed by more subjective estimation (four steps) if insufficient objective data are available. The method developed was applied to an Australian food composition database (AUSNUT2007) as an example.Results:Out of the 3874 foods available in AUSNUT2007, 2977 foods (77%) were assigned an estimated value on the basis of objective measures (steps 1–6), and 897 (23%) were assigned a subjectively estimated value (steps 7–10). Repeatability analysis showed good repeatability for estimated values in this method.Conclusions:We propose that this method can be considered as a standardised approach for the estimation of added sugar content of foods to improve cross-study comparison.

Best practice principles for community-based obesity prevention: development, content and application

Best practice in obesity prevention has generally been defined in terms of ‘what’ needs to be done while neglecting ‘how’. A multifaceted definition of best practice, which combines available evidence on what actions to take, with an established process for interpreting this information in a specific community context, provides a more appropriate basis for defining the principles of best practice in community‐based obesity prevention. Based on analysis of a range of literature, a preliminary set of principles was drafted and progressively revised through further analyses of published literature and a series of consultations. The framework for best practice principles comprises: community engagement, programme design and planning, evaluation, implementation and sustainability, and governance. Specific principles were formulated within this framework. While many principles were generic, distinctive features of obesity prevention were also covered. The engagement of end‐users influenced the design of the formatting of the outputs, which represent three levels of knowledge transfer: detailed evidence summaries, guiding questions for programme planners and a briefer set of questions for simpler communication purposes. The best practice principles provide a valuable mechanism for the translation of existing evidence and experience into the decision‐making processes for planning, implementing and evaluating the complex community‐based interventions needed for successful obesity prevention.