November 27th, 2015
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It often seems as if the period from Labor Day in September through Halloween in October, Thanksgiving in November, Christmas in December, New Year in January, Valentine’s Day and the football playoffs in February are designed to promote overeating. It is a wonder we all are not obese. So amid the food celebration and token diet advice, it’s nice to have some solid, research-based exposition of the myths surrounding weight loss and weight gain. We have one, thanks to Kevin Hall, Ph.D., a distinguished researcher at the National Institutes of Health. (For coverage of Dr. Hall’s recent work, click here.)
January 30th, 2015
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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.
January 5th, 2015
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So, our popular culture, as well as many physicians, believe that increased physical activity can either prevent obesity or bring about weight loss. The Today Show is an example of this popular, if wrong, view.
Lost in all this panting-cries for more steps are the actual research results. So it was interesting to find this interview at the University of Delaware annual Foltyn Family Health Sciences Seminar with Dr. Amy Luke of Loyola University Chicago. Dr.Luke has a distinguished career and a host of peer-reviewed publications.
Dr. Luke has been at the epicenter of the debate over whether it is energy intake or energy expenditure (i.e. physical activity) that is the cause of the obesity epidemic. Her research has taken her to rural Ghana, the Seychelles, urban South Africa, Jamaica, and the U.S. Using objectively measured criteria (stable isotope techniques and accelerometers in five cohorts) Luke found that in developing countries, residents were not expending significantly more energy than those in developed nations like the U.S.
She told the U.Delaware audience, “Physical activity is important for a whole host of health benefits, but it may not be as important as we thought in the prevention of obesity. This points to the need for strong objective measures of the factors on which we are basing public policy.” (Michelle Obama: are you listening?) Dr. Luke has concluded that it is diet, not physical activity, which is responsible for the obesity epidemic
May 29th, 2014
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Michelle Obama is launching a passionate defense of improvements to the National School Lunch Program. She is fighting House Republican proposals to provide waivers of the new requirements for some schools. The arguments against such waivers might be stronger had waivers not been so liberally used in the implementation of the Affordable Care Act. Nevertheless, the First Lady is making much of improvements in children’s health since launching her Let’s Move campaign. Unfortunately, the facts are not very supportive. The National Center for Health Statistics has issued a new report on cardiorespiratory fitness among U.S. youth aged 12-15. Short answer: it has gotten worse. The Report states, “The percentage of youth aged 12-15 who had adequate levels of cardiorespiratory fitness decreased from 52.4% in 1999-2000 to 42.2% in 2012.”
January 14th, 2014
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The National Center on Health Statistics has issued a report on physical activity in US youth aged 12-15 in 2012. They found (based on self-reports) that one-quarter of US youth engage in moderate to vigorous physical activity every day (excluding gym classes). 7.6% engaged in no physical activity on any day of the week. Slightly more boys engaged in daily physical activity than girls. 18% of boys with obese engaged in daily physical activity compared to 29.5% of normal-weight and 29.5% of overweight boys. Among girls, there was a similar pattern although the differences were not significant.
The report notes that the relationship between obesity and physical activity is not clear cut. While it is widely assumed that low physical activity precedes obesity, there is evidence that it is high body weight which precedes low physical activity.
The results somewhat track a recent study of leisure-time physical activity in adults which found that only 25% engaged in leisure time physical activity, although the trend was showing a decline in no leisure time physical activity.
December 16th, 2013
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Researchers generally agree that something happened in the 1970’s to cause the rise in adult and childhood obesity. Just what the cause (or causes) may be are highly debated. Clearly, there were changes in American society. While a great deal of attention has focused on food marketing, rise of fast food outlets, increase television viewing, decrease in physical activity, less attention has been paid to what changes were happening to mothers. Earlier work has looked at the rise of maternal employment outside the home. Now comes Steve Blair and colleagues who have looked at changes in physical activity patterns between 1965 and 2010 among mother with older children (between 5 to 18 years) and mothers with younger children (under 5 years). They found a significant reduction in physical activity (housework, child care, laundry, food preparation, food cleanup, and exercise) and an increase in sedentary behavior (time in a vehicle and using screen-based media). They conclude, “Given the essential role of PA (physical activity) for health and the potential for the intergenerational transmission of obesity and obesogenic behaviors, these results suggest that maternal inactivity may be an important target for the primary prevention of chronic noncommunicable disease and obesity.”
November 5th, 2013
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Few studies and even fewer public health advisories address the adverse effects of physical activity on some people. In this video, Claude Bouchard addresses the adverse effects of exercise and future of personalized exercise regimes. Dr. Bouchard references one of his earlier papers reported here last year showing a nearly 10% rate of adverse metabolic events in physical activity. (Thanks to Obesity and Energetics for bringing the video to our attention.)
October 15th, 2012
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So how big an effect is physical inactivity? We hear all the time how terrible physical inactivity is but just how bad. Now comes an answer. Some 39 collaborators, part of the Lancet Physical Activity Series Working Group have published an analysis of the burden of physical inactivity on disease and life expectancy.
The researchers calculated population attributable fractions associated with physical inactivity “using conservative assumptions for each of the major non-communicable diseases by country, to estimate how much disease could be averted if physical inactivity were eliminated.”
They estimated that, worldwide, physical inactivity causes, for coronary heart disease, between 3.2% in southeast Asia to 7/8% in the eastern Mediterranean. For type 2 diabetes, physical inactivity contributes 7%, 10% of breast cancer and 10% of colon cancer. “Inactivity,” they calculate, “causes 9% or more of premature mortality or more than 5.3 million of the 57 million deaths that occurred worldwide in 2008. If physical inactivity were eliminated, life expectancy of the world’s population would increase by 0.68 years (range of 0.41-0.95).
That’s it? 8 months? Well, that’s for both the active and inactive population. If you look at just having the physically inactive reach recommended levels of physical fitness, it is estimated that inactive people would gain 1.3 to 3.7 years from age 50 on in the United States. In East Asia, life expectancy from age 30 increased by 2.6 to 4.2 years. That’s a bit more meaningful. PubMed: Effect of physical inactivity on major non-communicable diseases worldwide