Table 1 Evaluation design frame for interventions chosen

1. Active After School Communities Program [Child Care ⁵]. Runs 8 weeks in each of the 4 school terms.

Primary school children in Prep to Grade 6 (age 5-11 years).

Number ≈ 99 000

i) Extensive & "lumpy" salary costs, particularly for regional physical activity co-ordinators; ii) sub-optimal capacity utilisation; iii) cost data modelled, not empirically-based; and iv) BMI outcomes not commensurate with high cost structure.

2. Multi-faceted program, including education to improve nutrition & increase physical activity, without an active physical education component [School-based].

Children in primary school Grades 1 and 2 (commencing in Grade 1, age 6 years).

Number ≈ 114 630

i) Costs over 2 year-period taken as representative 'annual cost' as reflects concomitant cohorts; ii) included central & school coordination costs for national program, but not teacher time (as integrated into curriculum); iii) assumed uptake by schools does not vary by type of school (public or private); and iv) parent involvement encouraged as part of program but not costed.

3. Multi-faceted program, including education to improve nutrition & increase physical activity, with an active physical education component [School-based].

Children in primary school Grades 1, 2 & 3 (commencing Grade 1, age 6 years).

Number ≈ 114 630

i) Costs over 3 year-period taken as representative 'annual cost' as reflects concomitant cohorts; ii) included central & school coordination costs for national program, but not teacher time (as integrated into curriculum); iii) physical activity component may pose problem for primary schools without specialist physical education teachers; iv) assumed uptake by schools does not vary by type of school; and v) parent involvement encouraged but not costed.

4. Multi-faceted program [School-based] targeted at overweight and obese children.

Overweight or obese children aged 7-10 years (Grades 2-5) at combined primary/secondary school.

Number ≈ 17 000 over 4 years (4 200 each year)

i) Modelled as implemented over 4 years rather than implementing it to everyone eligible every 4 years; ii) involves a peer-led program using 8^th grade students, supported by counsellors, to help obese children in grades 2-5; iii) counsellors costed as publicly funded psychologists employed on part-time basis (different to trial).

5. Education program to reduce consumption of carbonated (fizzy) drinks [School-based].

Children in primary school 2 to 6 (age 7-11 years).

Number ≈ 595 000 implemented over 5 years (119,000 each year)

i) Capacity calculated on seeing 1/5^th of schools each year, not all schools every year; ii) assumes each child receives intervention once during primary school; and iii) assumption of no additional school staff costs as sessions presented by trained project staff.

6. Education program to reduce TV viewing [School-based].

Children in primary school Grades 3 & 4 (age 8-10 years).

Number ≈ 268 600

i) Modelling included national/state project officers to implement national program and full training costs for teachers, but not teacher time in the classroom (as integrated into curriculum); ii) 50% of schools participate in any one year; iii) assumed uptake by schools does not vary by type of school (public or private); and iv) parent involvement encouraged as part of program but not costed.

7. TravelSmart Schools [Schools/neighbourhoods & community organisations⁷]

Children in primary school Grades 5 & 6 (age 10-11 years).

Number ≈ 267 700

i) Large impact on cost-effectiveness from attributing a share of intervention costs to broader congestion, community & environmental objectives; ii) capacity utilisation not an issue for this intervention as 90% of costs are variable; and iii) cost data mostly modelled, not a strong empirical base.

8. Walking School Bus [Schools/neighbourhoods & community organisations].

Primary school children in Prep to Grade 2 (age 5-7 years).

Number ≈ 7 840

i) Extensive set-up & overhead costs; ii) poor capacity utilisation; iii) attribution of costs to non obesity objectives; iv) empirical data coming from early developmental period of WSB program in Vic, Australia.

9. Reduction of TV advertising of high fat and/or high sugar foods & drinks to children [Media & marketing].

All Australian children aged 5-14 years.

Number ≈ 2.4 million

Key issue is exclusion of costs other than cost of monitoring/enforcing compliance with revised regulation. Excluded costs include: changing the regulations; any additional food costs to families in switch from non-core to core; impact on revenue stream of advertising companies & producers of non-core foods.

10. Family-based GP program targeted at overweight and moderately obese children [Primary care services ^g]

Overweight or moderately obese children aged 5-9 years

Number ≈ 9 685

i) Intervention design includes costs of family participation, but no additional benefits are included from weight loss to family members other than the child; ii) potential for piggy-backing this intervention into other GP-based interventions; iii) low % of fixed costs means cost drivers for affordability (patient numbers), do not impact much on cost-effectiveness; and iv) majority of cost incurred by government, but cost impact on family still significant, with time costs a major factor.

11. Family-based targeted program for obese children [Primary care services⁹ + hospital setting delivery by multidisciplinary team]

Obese children aged 10-11 years.

Number ≈ 5 800

i) Recruitment component adjusted from screening in schools in RCT, to opportunistic recruitment via GPs; ii) assumed 50% of 6,000 GPs already have calibrated scales and stadiometers necessary to measure weight; iii) 'intention to treat' approach adopted for costing (i.e. non completion still involved intervention costs), but full completion of visits required before benefits attributed.

12. Orlistat therapy for obese adolescents [Primary care services⁹].

Obese adolescents aged 12-16 years.

Number ≈ 3 256

i) Modelling incorporated opportunistic recruitment in Australian primary care setting (by GPs with dieticians providing dietary advice) and conservative adherence rates (65%); ii) only patients responsive to Orlistat assumed to continue past 2-week run-in period; iii) costs to parents in accompanying adolescent included; iv) high proportion of costs falling on patients/families (as Orlistat not on Pharmaceutical Benefits Schedule) impacts on access.

13. Laparoscopic adjustable gastric banding (LAGB) for morbidly obese adolescents [Hospital¹⁰].

Severely obese adolescents, aged 14-19 years, with private health insurance

Number ≈ 4 120

i) Definition of 'current practice'; ii) inclusion in costing of ongoing follow-up, including regular consultations and 2 LAGB replacements over lifetime; iii) cost data coming from early developmental period of LAGB (case series of 28 patients) extrapolated to eligible adolescent population; and iv) management of co-morbidities assumed to be same for intervention and comparator.

Protocol issues common to all interventions: i) Inclusion of time costs for adults/carers, but not children/adolescents; ii) exclusion of production gains/loses; iii) exclusion of unrelated costs in rest of life; iv) 'steady-state' costing, with program modeled in accordance with efficacy potential, assuming trained staff and infrastructure available; v) costs offsets based on mean reduction in BMI continuing over life of the child; vi) early set-up & development costs excluded (i.e. costs incurred before intervention commences, such as development of training packages); vii) annuitisation of capital, including human capital costs like training; and viii) full pathway costing, including recruitment and coordination.