Why Are Public Weight Loss Programs Not Effective?

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Public health programs such as First Lady Michelle Obama's "Lets Move" aren't going to win the fight against obesity because they require high levels of personal resources, according to U.K. researchers.

However, interventions that limit people's choices rather than rely on their self-motivation, such as regulating how stores sell unhealthy foods, might work better, stated Jean Adams, PhD, of the University of Cambridge in England, and colleagues.

"In England, the government's current 'flagship' obesity prevention programme is Change4Life. This social marketing campaign uses mass media and other avenues to inform and educate the public about the harms of excess weight and the benefits of being more active and eating more healthfully. Simple strategies for changing behaviour are also offered. Similar programmes operate elsewhere, including MangerBouger in France and Let's Move! in the United States," Adams and colleagues wrote in a policy paper in PLOS Medicine.

"The obvious assumption of these programmes is that advice, guidance, and encouragement will change the population's diet and activity behaviours. We explore why this is unlikely to be the case and why such strategies are unlikely to reduce inequalities in diet and obesity. We propose a framework that captures a wider range of intervention strategies and discuss how these may be used to improve diet, reduce obesity, and tackle inequalities," they wrote.

But U.S. and Canadian experts who spoke with MedPage Today offered mixed reviews on the policy paper, suggesting that the causes of obesity are too complex to be significantly impacted by public health regulations.

Analysis Details
Adams and colleagues pointed out that when it comes to encouraging public health, population and high-risk approaches interventions are commonly used. These are are delivered across an entire population without first identifying those at increased risk of disease. These interventions then differ in the degree of "agency," or use of personal resources and self-motivation, that they require.

The authors used the promotion of folic acid in pregnancy as an example.

A woman trying to conceive can be given an educational leaflet encouraging her to take folic acid supplements. In order for this high-agency population intervention to be effective, the woman must read the leaflet, understand the information presented, purchase the supplements, and then take them. Attrition might be expected at each of these at each of these steps, the authors noted.

"In contrast, if all commercial wheat flour is fortified with folic acid (a low-agency population intervention), one of the few, if only, steps at which attrition can occur is the decision to keep consuming products made with commercial wheat flour," they explained.

'Twin Public Health Aims'
The authors argued that low-agency population interventions are more likely to achieve the "twin public health aims of preventing disease and minimising inequalities. These interventions should, therefore, form the backbone of public health strategies."

In an email to MedPage Today, Adams outlined several interventions she thought would be effective and relatively easy to implement, and she discussed the evidence for each:
Sugary drinks tax: Emerging evidence from Mexico suggests that their 10% tax has reduced sales by about 10%, Adams said. "In Berkeley in California, they have early evidence that their tax was passed onto consumers in the form of increased prices -- and not just absorbed by producers. We think this is going to be implemented in the U.K. ... but, often there is political, public and commercial opposition to taxes such as this."

Advertising restrictions: Some health groups have called for a ban on television advertising of less healthy foods before 9 p.m., Adams said. "As far as I'm aware no country has tried a 9 p.m. watershed," she said. However, Adams noted that current U.K. restrictions on less healthy advertising during children's programs didn't have any impact on children's exposure to the advertisements. The ads simply moved from children's programs to other family-type programs that kids watch, she said.

Regulating shops: Scotland has introduced new rules that ban multi-buy offers on sweets and mandate that no more than 30% of drinks displayed can be sugary drinks. "Again, these are things that, as far as I'm aware, haven't ever been tried in large-scale settings before. We await the results of an evaluation that NHS Scotland has commissioned," Adams said. "The evaluation will also provide learning on problems with implementation in practice."

'Eat Less, Move More' Paradigm
Emily Dhurandhar, PhD, a spokesperson for The Obesity Society , and Arya Sharma, MD, PhD, clinical co-chair of the Alberta Health Services Obesity Program in Canada, agreed that programs such as "Let's Move" are not entirely effective.

"Programs like these don't necessarily do any harm, and they can be useful for some of the population. But largely, what we see in the data is that these programs have a small effect. They don't seem to have the impact we originally hoped for," Dhurandhar told MedPage Today.

"The public health discussion about obesity has been dominated by the 'eat less, move more' paradigm, but there's evidence that these might not be the main factors driving the obesity epidemic," Sharma told MedPage Today. "It's not that eating and physical activity are not important -- they are just not the whole story."

The causes of obesity are complex, and may include everything from sleep disturbances and stress to changes in gut bacteria. "Ten obese people will visit my clinic, and for each one there's a different reason why they put on weight," Sharma said.

For this reason, public policy interventions such as the ones Adams suggested are also unlikely to be widely effective, Sharma said.

Dhurandhar agreed. "There is low evidence that these interventions would work. There have been mixed results from test studies." For example, studies have shown that rules limiting one type of unhealthy food simply drive people to consume others," she said.

What else can be done? "Public health officials can look for new opportunities to intervene and take a more comprehensive approach to obesity," Dhurandhar said. "They need to understand it is more complex. There are many factors that need to be addressed."

Adams' group acknowledged that high- and low-agency initiative may be best when they are used together. "For example, a hypothetical intervention involving fortification of flour with folic acid (a low-agency population intervention) that is highly publicised and discussed may raise awareness of the benefits of taking folic acid supplements during pregnancy and so prompt greater engagement with information leaflets about prenatal health (a high-agency population intervention)," they noted.

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