Bases for obesity public policies basically worthless

January 30th, 2015 by MorganDowney Leave a reply »

Policy-makers, employer wellness programs, many physicians, the First Lady and most of the public health establishment espouse lifestyle changes, especially increased physical activity as the way (with or without caloric restriction) to prevent and reduce obesity and its related cardiovascular diseases. Millions of dollars have been spent to get Americans to increase their physical activity levels. For such programs to succeed they must have accurate information on levels of physical activity in the general population.

Virtually all of the studies on which these leaders rely come from self-reported answers to questionnaires, especially the National Health and Nutrition Examination  Survey (NHANES). Richard S. Cooper and colleagues who have compared NHANES results to objective data from accelerometers in 3,370 adults. The results are pretty shocking. They found:

“The estimates of both vigorous and moderate activity were extremely low, and contrast dramatically with those obtained by self-report. Vigorous activity lasting even 1 minute was only observed in 2% of any of  gender-race/ethnic groups and a 10 minute episode of moderate activity- the intensity obtained by walking up stairs was recorded in only one-third of the participants on any day of monitoring. ..

The major finding from these analyses is the demonstration that the population that population estimates of activity levels from surveys by questionnaire are markedly at variance with those obtained by objective managements. As the only source available from past surveys, questionnaires have been used in analytic research and have informed public policy for the last 50 years. If the data presented here are correct, a re-evaluation of the conclusions from much of this literature would be required. For example, based on national survey data it was assumed in Healthy People 2010 that 23 percent of adults engaged in vigorous activity of more than 20 minutes per episode at least 3 times a week at the beginning of this decade. However, in the NHANES data presented here, <1% of the population achieved this level of expenditure. Likewise, current guidelines recommend 150 minutes of moderate or 75 minutes of vigorous activity per week for adults. Only 0.3%, or 10 of the 3,370 individuals in this sample achieved that level.

Despite the widely held perception that low levels of energy expenditure in activity is an important risk factor for obesity, prospective data do not support this view. Randomized trials, where activity levels are rigorously measured and no attempt is made to restrict calories, likewise show that even substantial increases in energy expenditure in exercise do not result in weight loss because of compensatory increases in intake. We conclude, therefore, that the associations observed in the NHANES data presented here between activity and relative weight are spurious – i.e. the direction of the causality is most likely from obesity to lower activity.”

Things are not any better on the energy-intake side. Self-reported energy intake values are far inferior to objectively measured double-labelled water method, rendering energy intake information virtually useless according to a letter from 15 distinguished obesity researchers in 2013. A similar group of distinguished made the observation that “this extreme lack of validation of self-reported energy intake can be credibly drawn about energy intake derived from self-reported energy intake measures.”

So, the ground of almost all obesity pubic policies regarding energy intake and expenditure is at least questionable and maybe misleading. A similar group of research leaders has concluded that, ” We argue here that it is time to move from the common view that self-reports of (energy intake) EI and  physical activity energy expenditure (PAEE) are imperfect, but nevertheless deserving of use to a view commensurate with the evidence that self-reports of EI and PAEE are so poor that they are wholly unacceptable for scientific research on EI and PAEE…it is unacceptable to use decidedly inaccurate instruments which may misguide health-care policies, future research and clinical judgment…Researchers and sponsors should develop objective measures of energy balance.”

The Obama Administration and the First Lady have shown their commitment to addressing obesity. Now is their time to get serious and direct the National Institutes of Health, the Food and Drug Administration and the Centers for Disease Prevention to combine efforts to develop more accurate and reliable measures.