Dr. Sharma's Obesity Notes

Thorkild Sørensen

Yesterday, at the ongoing XI International Congress on Obesity, the 2010 ICO Award for Population Science and Public Health was awarded to Thorkild Sørensen from the University of Copenhagen. His studies from the early 70’s found early signs of the impending obesity epidemic in young Danish military recruits as far back as the 1960s.

His studies further suggest that this increase in obesity was related to “birth cohort” effects and can likely be traced to perinatal environmental factors rather than to influences acting on school age kids or adults. Indeed, based on his findings, Sørensen strongly recommends that we take a careful look at the historical dimension if we hope to identify the root causes of the current obesity epidemic.

As it so happens, I also had the pleasure of attending the launch of the new Wadd Society for the History of Obesity, with presentations from Professors George Bray, Stephan Rossner, and David Haslam at this meeting. The aim of the society is to promote interest in the history of obesity ranging from medical and pharmacological aspects to those of fashion, culture, art, and literature.

As all of this perhaps serves to remind those of us working in the field of obesity, that we must be very cautious before jumping to conclusions regarding whether or not recent environmental changes such as sedentary lifestyles, fast food, sugary soft drinks, television, or any of the many other factors that are being discussed are truly the root causes of the epidemic. While none of these development would be considered “healthy”, conclusive evidence as to their actual role in the epidemic of obesity is far from conclusive.

AMS
Stockholm, Sweden

For more posts on ICO 2010 click here

No worries, I am already holding my ears to avoid the screams of protest that I expect to get in response to this post.

But the idea that working moms may well play a noticeable role in the development of childhood obesity is indeed one that is suggested by Angela Pinot de Moira and colleagues from University College London, UK, in a paper just published online in the American Journal of Epidemiology.

The premise is simple: one of the most dramatic demographic shifts in the last decades has been the proportion of moms that work. From being the exception in the 60s, to becoming pretty much the norm for the majority of mothers today, this demographic shift has undoubtedly had profound effects on family life.

Not surprisingly, some have argued, that not having a parent at home (and traditionally this used to be the mom) may very much increase the risk of weight gain in offspring.

Thus, not only do “latchkey kids” have more freedom to eat unhealthy foods and spend afternoons slumped in front of the TV or computer, but long hours at work can also leave moms (or dads) short of time to prepare healthy family meals (ergo the dramatic rise in fastfood and family restaurants).

In addition, working mothers (or dads) may also have to drive their children to school rather than have the time to walk them there and working partents certainly don’t have the time to watch over their kids on the playground all afternoon or be at home in case their kids scrape a leg falling off their bikes or get beaten up by the neighbourhood bully.

So is this hypothesis borne out by the data?

To address this question, the authors examined members of a 1958 British birth cohort (age 7 years, n=8,552) and offspring (ages 4-9 years, n=1,889) born to mothers under age 30 years to establish whether risk factors for childhood obesity have changed over time (1965-1991).

The authors found that the prevalence of overweight/obesity had increased by more than 50% between generations and that parental BMI was strongly associated with offspring BMI.

But perhaps more interestingly, full-time maternal employment turned out to be positively associated with offspring BMI in childhood with an increase of 0.4-0.5 units in kids with working moms. This relationship was in fact stronger in the offspring than in the original cohort.

Maternal employment was found to have increased by more than 30% across generations, as a result of which, the population attributable risk maternal employment increased from 3.1% to 7.8% across generations.

In addition, the authors noted that smaller family size and fewer younger siblings were also associated with increased childhood BMI.

As argued by Elizabeth Warren and Amelia Warren Tyagi in their bestseller “The Two Income Trap: Why Middle-Class Mothers and Fathers Are Going Broke“, even if all kinds of issues may be linked to working moms, simply asking moms to stay at home is neither feasible nor socially desirable (incidentally, both authors are working moms).

Rather, other measures, including proper and affordable day care, accessible and supervised after-school activities and more flexibility in working hours may help moms (and dads) better meet the demands of their kids, thereby hopefully reducing their risk for obesity.

I wonder what my readers think of this hypothesis and what (if anything) can (should) be done about it.

AMS
Edmonton, Alberta

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de Moira AP, Power C, & Li L (2010). Changing Influences on Childhood Obesity: A Study of 2 Generations of the 1958 British Birth Cohort. American journal of epidemiology PMID: 20488872

Yesterday’s news was all about the new report on the declining fitness and increasing fatness of Canadians.

Although the role of physical activity to combat excess weight remains disputable, there is absolutely no doubt that increased physical activity is the key to better physical fitness (at any weight!).

So how do we get Canadians moving?

Probably not by demanding that they exercise more - indeed, we could probably easily plot the increase in gyms, fitness clubs, joggers, and sales of home exercise equipment vs. the increase in obesity and get a straight line that leaps right off the top of our chart.

Somehow I very much doubt that throwing even more gyms, fitness clubs or exercise equipment at the problem is likely to make any difference whatsoever.

Not that these facilities or gadgets are not effective when used; it is just that they are only (and probably only ever will be) used by such a small fraction of the population (mostly younger, female and affluent) that their use will probably never have a noticeable impact on public health.

If we want Canadians as a population to be more active, we will have no choice but to address some of the key factors that have led to this dramatic reduction in physical activity: automation and built environments that promote car dependency.

As pointed out by James Woodcock and colleagues from the UK in a recent article in The Lancet:

“Creation of safe urban environments for mass active travel will require prioritisation of the needs of pedestrians and cyclists over those of motorists. Walking or cycling should become the most direct, convenient, and pleasant option for most urban trips.

An increase in the safety, convenience and comfort of walking and cycling, and a reduction in the attractiveness of private motor vehicle use (speed, convenience, and cost) are essential to achieve a modal shift.”

Based on their modeling of the impact of increasing active transportation in London, UK and New Delhi, India, together with the known benefits of increased physical activity, the authors conclude that:

“Increase in the distances walked and cycled would lead to large health benefits. Largest health gains would be from reductions in the prevalence of ischaemic heart disease, cerebrovascular disease, depression, dementia, and diabetes.”

Are these changes likely to occur across Canada anytime soon? Probably not!

Can we perhaps get Canadians to be fitter by hoping that they’ll now all get on their treadmills at the end of their eight hour working days and hour-long commutes? Don’t hold your breath!

Do you drive a car, complain about poor roads, expensive parking, and simply hate those pesky pedestrians and cyclists?

Then YOU are the cause of Canada’s fitness dilemma.

AMS
Edmonton, Alberta

I have previously linked the obesity epidemic to global warming, suggesting that the solution to one of these problems is likely the solution to the other.

Here is now another spin to this idea from a study by Kevin Hall and colleagues from the US National Institutes of Health, Bethesda, Maryland, just published in PLoS.

Hall and colleagues calculated the energy content of nationwide food waste from the difference between the US food supply and the food consumed by the population. The latter was estimated using a validated mathematical model of metabolism relating body weight to the amount of food eaten.

Their calculations show that the US per capita food waste has progressively increased by ~50% since 1974 reaching more than 1400 kcal per person per day or 150 trillion kcal per year (enough to feed ~150 Million additional people).

They further estimate that food waste now accounts for more than one quarter of the total freshwater consumption in the US and ~300 million barrels of oil per year (or ~1/3 of Alberta’s annual oil production).

In addition to the methane and CO2 emissions from the production of this food that no one needs, even more of these gases are produced as the food decomposes in landfills.

The researchers speculate that this increased availability of cheap food creates a “push” effect (now that we’ve gone to the trouble of producing it, let’s make sure it gets eaten), that promotes caloric overconsumption and the development of obesity.

As further pointed out in a discussion of this article in the ECONOMIST,

“The cheaper food is, the more likely it is to be thrown away even before it is sold to someone who might actually eat it. Such supply-chain waste can be built into the price, and usually makes economic sense. Throwing away leftovers is often better business than risking running out of stock. Yet any waste of a valuable resource is offensive at a visceral level.“

I could not agree more.

AMS
Edmonton, Alberta

Hat tip to Kavita for drawing my attention to this article

Amongst the many environmental factors that can promote the development of excess weight gain, one of the most intriguing and persistent notions is the possible role of obesogenic environmental toxins.

No doubt, the presence of environmental pollutants is associated with “westernisation” and many organic pollutants tend to accumulate in adipose tissue where they can have substantial metabolic effects - at least in theory.

But how good is the evidence that environmental pollutants can in fact affect adipocyte growth and function?

This issue was recently addressed by Robert Sargis and colleagues from the University of Chicago, IL, in a study just published in OBESITY.

This study focused on the potential contributions of environmental pollutants that act as endocrine disrupting chemicals (EDCs) on glucocorticoid signaling, a major driver of adipogenesis.

The researchers screened various EDCs and found that bisphenol A (BPA), dicyclohexyl phthalate (DCHP), endrin, and tolylfluanid (TF)) had significant stimulatory effects on the glucocorticoid receptor. Amazingly, even minute (picomolar) quantities of these compounds markedly promoted lipid accumulation and adipocyte differentiation in 3T3-L1 preadipocytes.

Importantly, these effects required the presence of a weak differentiating cocktail suggesting that the effects of these compounds is mediated through synergistic effects with known modulators of adipocyte differentiation. Thus, these compounds appear to act as “accelerators” rather than “inducers” of fat formation. 

These findings raise a number of interesting possibilities: for e.g. I cannot help but wonder whether drinking sugary pop out of a glass bottle is perhaps less obesogenic than drinking the same number of calories out of a BPA containing plastic bottle or can?

AMS
Sapporo, Japan