The Surgeon’s General ground-breaking Call to Action on overweight and obesity came out in 2001. Surgeon General: Call to Action: Obesity Since then, millions of dollars have been spent by governmental and non-governmental organizations on steps to prevent obesity, primarily in children. How’s it going? Well, in spite of the best of intentions of hundreds of people, not well.

A paper just out by Dr. Jeffrey Mechanick , a highly respected researcher in the field, and colleagues, looked at three anti-obesity policies: increasing physical activity in children, taxing sugar-sweetened beverages and funding for walking and biking trails. They found, “While numerous studies have established their efficacy when implemented on a local or communal (small-) scale, there is little published evidence demonstrating statistical correlation between BMI (body mass index) and implementation of these policies, or any combination, thereof, on a statewide (large-) scale.” They conclude, “American culture, policy-making, and the obesity epidemic constitute a recursive, complex adaptive system. We have proposed that an emergent property of this system is that implementation of anti-obesity policies may not be reducing the obesity growth rates as early as expected, if at all. This somewhat counter-intuitive finding is, on the surface, discouraging, but with deeper deliberation, offers redirection for an anti-obesity campaign. Since the obesity epidemic remains uncontrolled with vast downstream adverse effects, it is imperative to gain a thorough understanding of this complex system. The focus should be broadened to improve consumer dietary patterns and physical activity. There should be greater supply-side regulation of food content, as well as interventions targeting obesogenic inflammatory mechanisms. PubMed:Lack of Correlation between anti-obesity poliicy and obesity growth rates

This one paper is not alone. The Cochrane Reviews are distinguished for their rigorous study of important health topics. A Cochrane Review was published in 2011 evaluating all randomized clinical trials (RCTs) of interventions for preventing obesity in children. The review included an 55 studies. The majority of studies targeted children aged 6-12 years. The meta-analysis included 27,946 children. According to the authors, overall, the programs were effective, but not all were, reflecting a high degree of heterogeneity. Children in the intervention group had a standard mean difference in adiposity  (measured as BMI or zBMI) of –0.15 kg/m2 The authors urged that the findings be taken cautiously because of the unexplained heterogeneity and the likelihood that studies with negative outcomes were not published. Cochrane Review: Preventing Obesity in Children

A near-universal policy goal is increasing physical activity of children in school. Yet, even here, the evidence is poor to weak.

Cawley and colleagues examined the impact of state physical activity requirements on youth physical activity and overweight, using data from the Youth Risk Behavior Surveillance System for 1991, 2001, and 2003. They found that high school students with a binding physical education (PE) requirement report an average of 31 additional minutes per week spent physically active in PE classes. Their results indicate that additional PE time raises the number of days per week that girls having exercised vigorously or have engaged in strength-building activity. They found “no evidence” that PE lowers BMI or the probability that a student is overweight. They conclude that “there is not yet the scientific basis to declare raising PE requirements an anti-obesity initiative for either boys or girls. PubMed: Cawley: The Impact of state physical education requirements

A 2011 paper found that adequate PE time was inversely related to recess, and vice versa, suggesting that schools are substituting one form of physical activity for another, rather than providing the recommended amount of both recess and PE.  PubMed: Slater: The Impact of State Laws and District Policies