Effective interventions depend on understanding complex picture

Food marketing practices and institutionally driven reductions in activity are the two factors cited when physicians, policy makers, the media, and the public discuss causes of and solutions to the obesity epidemic. Given the scope of the problem and the evidence (or its lack), people should be thinking about obesity more critically and viewing seemingly obvious answers with some skepticism, says obesity expert and UAB biostatistician David B. Allison, PhD.

Allison and colleagues recently published a paper in the International Journal of Obesity (IJO) outlining the case for other causes of obesity beyond what he calls the “big two.” The paper explores 10 additional factors that may contribute to the epidemic (2006.30:1585-1594).

“Evidence for the big two as primary causes of obesity is largely circumstantial,” he says. “Yet there is a hegemony of ideas in which these factors are accepted explanations for the epidemic. When people believe causes are understood, there is little impetus to look further. This may result in well-intentioned but ill-founded proposals for reducing obesity.”

While the big two are plausible hypotheses for the obesity epidemic, the level of evidence implicating them as major players also exists for other factors, Allison says. “Our research found evidence as compelling, and in some cases, more so, for causes of obesity beyond the big two.” In the IJO paper, Allison et al offered these additional explanations for obesity:

1. Sleep debt: Sleep restriction increases obesity risk.
2. Pollution: Endocrine disruptors can increase body fat.
3. Air conditioning/heating: Thermoneutral zones reduce energy expenditure and increase food intake.
4. Decreased smoking: Smokers weigh less and gain weight after stopping.
5. Medications: Many pharmaceuticals cause weight gain.
6. Demographics: Older adults and some ethnic groups have higher obesity rates.
7. Increasing gravida age: Older maternal age may increase risk for obesity in offspring.
8. Intrauterine/intergenerational effects: Environmental changes in utero and as far back as two generations may influence obesity.
9. Obesity-fertility link: Moderately obese people may be more fertile than lean individuals, which may select for genotypes predisposed for obesity.
10. Union of obese spouses: Obese men and women tend to marry, which may increase risk of obese offspring.

“All these factors have increased in our society — some may have a small effect, but they may interact in ways that magnify their influence,” he says, noting 3 causes with especially clear evidence: reduced smoking, increased use of certain drugs, especially antipsychotics, and demographics. “Obesity rates have been rising for 100 years, with a major upswing starting in 1980 — the time when the first baby boomers turned 35, an age many people begin to gain significant weight. These 10 factors and others are worthy of further study, and given positive results, some are worthy of intervention. To avoid spending resources on interventions that may not work, we need to better understand the complex picture of obesity.”

For more information
Dr. David Allison
1.800.UAB.MIST
mist@uabmc.edu