CANCER PREVENTION INSTITUTE OF CANADA

Last updated: 15-Jan-2007

Combined Interventions

As in many other areas of health promotion and prevention, comprehensive programs incorporating multiple intervention categories are popular approaches in weight loss. Combining diet, exercise and counselling for optimal and sustainable weight loss makes good intuitive sense. However, there are still large gaps in understanding the individual and combined role of diet, exercise, and counselling in different settings.

Community-based Interventions

The conclusion of the World Health Organization in 2000 was that there had not yet been any “well-evaluated and properly organized public health programmes aimed at the population-level management or prevention of obesity.”[1] This suggests the need for more program development and more outcomes research.

School-based Interventions

A total of 5 trials were included in a 2002 systematic review.[2] The multifaceted interventions usually included both diet and physical activity education and sometimes actual exercise periods. Significant reductions in body fat were observed in some projects. Ironically, an architect of Singapore’s decade-long school program equated their results to one of the least successful trials noted above. However, there have been positive results in Singapore over the long-term, i.e., about a 2% decline in obesity rates among 11-12 and 15-16 year olds, which was statistically and clinically significant.[3] (In general, that country has seen success in its health promotion and chronic disease control efforts, which were further intensified in 2000.[4]) Another school-based program that takes a comprehensive health approach is the Kiel Obesity Prevention Program (KOPS) in Germany.[5]

Clinical Interventions

The evidence concerning combined clinical programs is limited, but generally the results of weight loss trials involving multiple interventions continue to be equivocal.[6] For example, a 1994 RCT that added exercise and behaviour therapy to diet did not show statistically significant additional weight changes.[7] A similar result was seen in another project where exercise and cognitive-behavioural therapy were added to diet.[8] The pooled results from several RCTs of exercise added to diet and behaviour therapy showed an additional weight loss of only 3 kg at 12 months and just over 2 kg at 24 months.[9] By comparison, the results of 11 studies of diet, behaviour therapy and exercise versus no intervention control showed an overall weight loss at 12 months of 4 kg, similar to that of diet programs combined with drug therapy.[10] Weight regain continues to be a concern even with multiple interventions. All combinations of diet, exercise, and behaviour therapy showed more weight loss at 12 months than at 24 months.[11]

“Binary” studies where a single treatment is added to diet have produced the clearest positive results for weight loss, an assessment that was confirmed in the recent HTA report.[12] The two most effective combinations are adding exercise to diet or behaviour therapy to diet. Pooled results from 5 studies showed a modest reduction of about 2 kg at 12 months with exercise added to diet.

Combined results from 4 studies where behaviour therapy was added to diet showed positive results against diet alone up to 5 years, as seen in the following table.[13]

Overall, one reviewer concluded that the most effective counselling-based weight loss interventions are those sustained over the long-term and which focus on diet and exercise in a multidisciplinary way.[14]

Regulatory and Economic Interventions

Policies aimed at environments are unproven. Some would say that the urgency of the obesity problem should prompt action anyway, whereas others call not for the adoption of specific policies, but instead for immediate and intensive research.[15] For instance, the evidence linking BMI to types of land-use mix have been contradictory.[16] In general, the analysis of determinants within obesogenic environments is complex.[17],[18],[19]

Development of policy to inform macrosystem changes, e.g., healthier built form in urban settings, will require political will at various levels of government. Coalition-building and increasing public support can begin with working together on smaller initiatives. Some of these environmental initiatives need to begin right away with children, adolescents, and their families (see the relevant section under Key Issues below). As a recent Australian initiative concluded: “Obesity develops over time and once it has developed, it is difficult to treat. The prevention of weight gain, beginning with childhood, offers the most effective means of achieving healthy weight in the population.”[20]

Comprehensive Interventions

A case was made earlier in this report for assembling comprehensive plans on the absence of complete results data. An example of a best-practice approach for physical activity and other health improvement has just been launched in B.C.[21] Although Action Schools! B.C. (ASBC) is the “headline” component, it really is part of a planned initiative by the government that encompasses both physical activity and diet. The proposed plan, which is directed at students, includes:

• expanding the physical activity pilot project (ASBC) to the whole province and all grades
• discontinuing junk food sales in schools (within four and half years, a time lag that is not fully explained)
• promoting healthy food
• recognizing schools that make strides on program implementation and see results
• with local and national partners, researching and developing a wider framework for health promotion, including new standards for physical education and health curricula

ASBC itself has 6 levels of intervention, namely, encouraging:[22]

• policies that enhance an ‘environment of opportunity’ for physical activity
• scheduling at least 150 minutes of physical education per week
• adoption of classroom-based physical activity ideas
• partnerships with families and community practitioners
• expanded options for extracurricular physical activity
• communication in the school that builds enthusiasm for the program goals

An 18-month pilot project consisted of 7 intervention schools and 3 controls. At the end, intervention schools had averaged 49 more minutes per week of physical education, exceeding the target amount. As a result, aerobic fitness improvement was higher than in control schools (39 vs. 17%), as were other measures of cardiovascular health and bone mass. Several other indicators, including vegetable and fruit intake and average body fat, did not improve. The latter result was expected, as the pilot period was deemed too short to see changes in body weight (as other weight control programs do see results after 18 months, especially those which add dietary interventions to exercise)

[2] University of York. The prevention and treatment of childhood obesity Effective Health Care 2002; 7(6).

[3] Toh CM, Cutter J, Chew SK. School based intervention has reduced obesity in Singapore British Medical Journal 2002; 324: 427.

[4] Toh CM, Chew SK, Tan CC. Prevention and control on non-communicable diseases in Singapore: a review of national health promotion programmes Singapore Medical Journal 2002; 43(7): 333-9.

[5] Muller MJ, Asbeck I, Mast M et al. Prevention of obesity—more than an intention International Journal of Obesity 2001; 25(Suppl 1): 66-74.

[6] Liao K. Cognitive-behavioural approaches and weight management: an overview Journal of the Royal Society of Health 2000; 120(1): 27-30.

[7] Blonk MC, Jacobs MA, Biesheuvel EH et al. Influences on weight loss in type 2 diabetic patients: little long-term benefit from group behaviour therapy and exercise training Diabetic Medicine 1994; 11(5): 449-57.

[8] Avenell A, Brown TJ, McGee MA et al. What interventions should we add to weight reducing diets in adults with obesity? A systematic review of randomized controlled trials of adding drug therapy, exercise, behaviour therapy or combinations of these interventions Journal of Human Nutrition & Dietetics 2004; 17(4): 293-316.

[9] Avenell A, Brown TJ, McGee MA et al. What interventions should we add to weight reducing diets in adults with obesity? A systematic review of randomized controlled trials of adding drug therapy, exercise, behaviour therapy or combinations of these interventions Journal of Human Nutrition & Dietetics 2004; 17(4): 293-316.

[10] Ibid.

[11] Ibid.

[12] Ibid.

[13] Ibid.

[14] Raine KD. Overweight and Obesity in Canada: A Population Health Perspective. Centre for Health Promotion Studies, University of Alberta, 2004.

[15] Ibid.

[16] Rutt CD, Coleman KJ. Examining the relationships among built environment, physical activity, and body mass index in El Paso, TX Preventive Medicine 2004 (in press).

[17] Swinburn B, Egger G, Raza F. Dissecting obesogenic environments: the development and application of a framework for identifying and prioritizing environmental interventions for obesity Preventive Medicine 1999; 29(6 Pt 1): 563-70.

[18] Carter MA, Swinburn B. Measuring the 'obesogenic' food environment in New Zealand primary schools Health Promotion International 2004; 19(1): 15-20.

[19] Hinde S, Dixon J. Changing the obesogenic environment: insights from a cultural economy of car reliance Transportation Research Part D 2005; 10: 31-53.

[20] National Obesity Taskforce, 2003. Healthy Weight 2008 Australia’s Future: The National Action Agenda for Childen and Young People and their Families. Source: http://www.asso.org.au//freestyler /gui/files/healthy_weight_2008.pdf (accessed December 2004).

[21] News Release. Province launches plan to help students get healthier. November 23, 2004.

[22] Backgrounder. Comprehensive plan to promote student health. November 23, 2004.