Posts Tagged ‘Environment’

Obesity The Irish Way: No Blame, No Shame

January 27th, 2012

A few weeks ago I wrote about how Ireland is dealing with its obesity epidemic. I call it the “No Blame, No Shame” approach. Ever since my visit with the Irish government’s point person on obesity, I have been trying to think about “obesity” without thinking about “blame”. I recall that the first media call when I took over the American Obesity Association asked me, “Who is to Blame?” It seems to me still that we cannot move beyond blame.

So, it was with some interest that I read this report from The Lancet about the British Government’s new approach to move from nudging patients to a healthier lifestyle to nagging them which The Lancet’s editors predicted will be a failed policy. Public health in England: from nudge to nag : The Lancet

On the other hand, this editorial in the Irish Times points out something I think is obvious:

“Negative lifestyle messages lead to stigmatisation, victim-blaming and health inequalities. Discussing obesity and diabetes as if these problems are the individual’s fault stigmatises people with weight problems. Everyone may feel fearful when listening to health experts being interviewed about the latest lifestyle report, but only those in the higher socio-economic groups are able to comply with the message to, say, eat more fruit and veg. Poor people stay scared with no way of alleviating their fear. Telling people to exercise more is pointless if they live in an area with no facilities and no footpaths”. Forget lifestyle advice, it’s policy that matters – The Irish Times – Tue, Jan 03, 2012

The editorial goes on to call on the government to enact policies which change the food/physical activity environment.

Nagging or positive improvements? What’s the choice?

 

It’s 10 O’Clock. Do you Know Where Your Genes Are?

October 5th, 2011

There was a very important story in the New York Times on October 4, 2011 about obesity but you are forgiven if you missed it.  The piece, by Nicholas Wade, tells the story of research on the histories of childbirths on an island in the St. Lawrence River, 50 miles northeast of Quebec. What they found was that the age at which women had her first child fell to 22 years from 26 years from 1799 to 1940. What did you miss? Well, it turns out that the age at which a woman has her first child is a highly heritable trait. And what this finding means is that humans are still evolving.  Statistical tests allowed the researchers to distinguish between the effects of natural selection and changes in cultural practices. Natural Selection Leaves Fresh Footprints on Canadian Island – NYTimes.com

(Readers may recall that the above time-frame is not unlike that employed in The Techno-Physio Revolution, which documented the rise in body weight over 350 years.)

 Not only are humans still evolving but that evolution is occurring faster than many assume.  The DNA sequence can only identify large changes sweeping through a population. But phenotypic or bodily data can provide information on more recent changes.  Wade cites a review article of 14 studies. The lead author, Stephen C. Stearns of Yale,  stated, “We had three general aims: first, to correct the still widespread misconception that natural selection is not operating on contemporary humans; second, to make quantitative predictions about future evolutionary change for specific traits with medical significance; and third, to register firmly a point of general cultural interest that follows directly from our first two aims: We are still evolving, and for some traits we can make short-term predictions about our future evolution.” In this study, the authors found that the descendants of women in the Framingham Heart Study, begun in 1948, are predicted to be on average slightly shorter and stouter, to have lower total cholesterol levels and systolic blood pressure, to have their first child earlier and reach menopause later than they would in the absence of evolution. Colloquium papers: Natural selectio… [Proc Natl Acad Sci U S A. 2010] – PubMed – NCBI 

Jeffrey Friedman noted in the essay I quoted yesterday, “natural selection can be observed in a single generation as nature weeds out the maladapted under changing environmental conditions, leaving the more highly adapted individuals to proliferate. Thus, rapid changes in population characteristics are generally the result of a gene/environmental interaction.” 

What does this have to do with obesity? Well, in discussions about the genetic basis of obesity, skeptics often comment is often that increases in the prevalence of obesity (basically in the last 50 years) cannot be the result of genes because the gene pool or natural selection does not change that rapidly. Yet, evidence to the contrary continues to mount. While no one may be sure just how fast the genome is changing, it is probably inaccurate to say that it cannot change quite rapidly. 

Indeed, an examination of 23 studies reporting data from 14 different countries between 1998 and 2008, indicates a high prevalence of overweight and obesity in pre-school children age 2-5 years, in middle and high income countries, among both well-off and low income segments of populations, in both rural and urban areas and among all ethnic and racial groups represented. Global prevalence of overweight and obesity in… [Anthropol Anz. 2011] – PubMed – NCBI

New Insight on Gene-Environment Interaction

July 9th, 2011

For many people, understanding obesity is a pretty straightforward proposition. Eat more you gain weight. Eat less you lose weight. The laws of thermodynamics. Energy in v. Energy out. End of story. Alas, we know it is not that simple. For one thing, we know that obesity is highly inheritable. For another, we know that changes in the environment can produce rapid changes in the prevalence of obesity in the population. But, while finding many genes and their variations (called alleles) have been identified, they account for only about 2% of the total genetic variation in BMI. Skeptics doubt a genetic explanation arguing that the gene pool cannot change as quickly as the current changes in obesity. (These folks have tended to see the obesity epidemic as a 75 year phenomenon. But see the book review on The Changing Body, for how long this change has been going on..around 350 years.)  On the other hand, the environmental approach has raised the question, “If the environment is so prone to creating obesity, why isn’t everyone obese?” This line of doubt is reinforced by high variations in obesity in small geographic areas.

So now Danish researchers have use the Danish Twin Registry to try to explain the interaction of genes and the environment. The Danish Twin Registry contains information on virtually all twins born in Denmark since 1870. Two groups were surveyed. What they found was that the environment may modify the genetic expression related to obesity. This environmental effect grows stronger, but only for some individuals and not for others. They estimate that there is a 33.3% increase in the expression of adiposity-related genes associated with a 10% increase in the prevalence of obesity. They conclude that the genetic architecture of obesity should not be considered independent from the environmental context. PLoS ONE: Increased Genetic Variance of BMI with a Higher Prevalence of Obesity

The Causes of Obesity: There’s more than you think

September 30th, 2010

September 30, 2010

Perhaps the greatest gap between science and policy-making is the understanding of the causes of obesity. For most of the public and policy-makers, it is beyond discussion that obesity is caused by poor diets and lack of physical activity. Scientists, on the other hand, know that, without diminishing the roles diet and exercise play, they are not the whole story.  Obesity is far more complex. This gap has significant implications. Billions of dollars have been spent on strategies which, to be kind, are simplistic. Not only is this wasteful, it distracts or delays our understanding and the development of more effective remedies. Probably no better description, in great detail, of the ‘putative’ causes of obesity is contained in this article by McAllister and a prestigious group of co-authors. Ten putative contributors to the obesity epidemic. [Crit Rev Food Sci Nutr. 2009] – PubMed result. Even if the article is a bit dense, it is worth it to make us all more humble in approaching this disease.

The Built Environment

September 27th, 2009

Understanding the Relationship between Activity an…[BMC Public Health. 2009] – PubMed Result

Prevalence, trends and environmental influences on…[Med Sport Sci. 2007] – PubMed Result

Built Environments and Obesity in Disadvantaged Po…[Epidemiol Rev. 2009] – PubMed Result

Neighborhood environments: disparities in access t…[Am J Prev Med. 2009] – PubMed Result

Physical environmental correlates of childhood obe…[Obes Rev. 2009] – PubMed Result

Genetic Basis of Obesity

September 26th, 2009

Often one hears it stated that obesity is not a genetic disease. If by that the speaker is saying that obesity is probably not due to a single genetic change they are not quite right. There are some rare forms of obesity which are due to a single gene change. Genetic obesity syndromes. [Front Horm Res. 2008] – PubMed Result; Genetic and hereditary aspects of childhood obesit…[Best Pract Res Clin Endocrinol Metab. 2005] – PubMed Result But if they mean a single genetic change cannot account for a worldwide epidemic of obesity occurring over the last 30 years they are probably right. If the speaker means it is unlikely that there will be a treatment for obesity based on gene therapy, they are probably correct. (Although who can predict the future?) However, they miss the point if they do not understand that for millions of years of evolution, the species we call humans have favored genes which maximize its chances for survival and reproduction. So our taste preferences, our physical activity preferences and the like are passed on in the genome and our part of our inheritance. The problem is that for centuries we humans lived in an environment which was totally different than the one we live in now. The disconnect is that our bodies have not yet adapted to this new world where tasty, nutritious food is readily available and where most of us do not have to expend anything other than a minimal effort to obtain it, survive and flourish. Anything policy-makers or parents want to do about obesity must be understood in the context of the powerful force evolution has been in designing how humans acquire, store and use energy from food.

According the CDC:

  1. Biological relatives tend to resemble each other in many ways, including body weight. Individuals with a family history of obesity may be predisposed to gain weight.
  2. Different responses to the food environment are largely due to genetic variation between individuals.
  3. Fat stores are regulated over long periods of time by complex systems that involve input and feedback from fat tissue, the brain and endocrine glands like the pancreas and the thyroid. http://www.cdc.gov/genomics/training/perspectives/files/obesknow.htm,
  4. The tendencies to overeat and be sedentary, the diminished ability to use dietary fat as fuel and enlarged, easily stimulated capacity to store body fat are all genetically influenced. The variation in how individuals respond to the food rich environment and the differences in acquiring obesity related comorbid conditions are also genetically determined. http://www.cdc.gov/Features/Obesity/

Since 1997, published studies have found that variation in BMI is largely due to heritable genetic differences, with estimates ranging from 55% to 85%. A 2008 study found that 77% of the adiposity in preadolescent children born since the start of the obesity epidemic was due to genetic inheritance compared to 10% for the environment. Evidence for a strong genetic influence on childho…[Am J Clin Nutr. 2008] – PubMed Result

A fast rate of eating appears to be heritable. Eating rate is a heritable phenotype related to we…[Am J Clin Nutr. 2008] – PubMed Result Differences in responding to the obesogenic environment may also be heritable Genetic influence on appetite in children. [Int J Obes (Lond). 2008] – PubMed Result and Appetite is a Heritable Phenotype Associated with …[Ann Behav Med. 2009] – PubMed Result. The FTO gene may be involved. The FTO gene and measured food intake in children. [Int J Obes (Lond). 2009] – PubMed Result and Increasing heritability of BMI and stronger associ…[Obesity (Silver Spring). 2008] – PubMed Result Parental leanness appears to provide strong protection against the development of obesity in children. Development of overweight in children in relation …[Obesity (Silver Spring). 2009] – PubMed Result

There is an interesting scientific debate about what is called the “thrifty gene” hypothesis about how a genetic preference for storing extra energy on our bodies might have developed. Thrifty genes for obesity, an attractive but flawe…[Int J Obes (Lond). 2008] – PubMed Result and The clinical biochemistry of obesity. [Clin Biochem Rev. 2004] – PubMed Result. Some think that childhood obesity is increasing due to ‘associative mating’ by overweight parents who pass on their genetic disposition to obesity to their children. Childhood obesity: are genetic differences involve…[Am J Clin Nutr. 2009] – PubMed Result

The evidence for the genetic basis of obesity, in addition to environmental changes is quite strong. See Implications of gene-behavior interactions: preven…[Obesity (Silver Spring). 2008] – PubMed Result; Genome-wide association scan shows genetic variant…[PLoS Genet. 2007] – PubMed Result and The genetics of obesity. [Metabolism. 1995] – PubMed Result

The environment is thought to be responsible for variations between populations but genetics is responsible for the variations within a given population. Obesity – Missing Heritability and GWAS Utility and Genetic and environmental factors in relative body…[Behav Genet. 1997] – PubMed Result. Genetics may account for many cases of morbid obesityFamilial aggregation of morbid obesity. [Obes Res. 1993] – PubMed Result.

Genetics may play an important role in determining who can benefit from different types of intervention. Implications of gene-behavior interactions: preven…[Obesity (Silver Spring). 2008] – PubMed Result or who is more likely to be affected by obesity Ethnic variability in adiposity and cardiovascular…[Int J Epidemiol. 2009] – PubMed Result. Or experience a comorbid condition like Type 2 diabetes Mechanisms of disease: genetic insights into the e…[Nat Clin Pract Endocrinol Metab. 2008] – PubMed Result

The FTO gene is currently under active research interest for providing a link to how obesity related conditions might arise and how patients can benefit from this knowledge. FTO: the first gene contributing to common forms o…[Obes Rev. 2008] – PubMed Result Genome-wide association scan shows genetic variant…[PLoS Genet. 2007] – PubMed Result

The FTO gene may explain different responses to exercise. FTO Genotype Is Associated With Exercise Training-…[Obesity (Silver Spring). 2009] – PubMed Result .Physical activity and the association of common FT…[Arch Intern Med. 2008] – PubMed Result

A factor in the resistance to describe obesity as a genetic disease may be in the assumption that the human genome does not change rapidly whereas the increase globally in the rates of obesity have occurred in the last 40-50 years. However, evolutionary biologists are debating the speed of genetic change. In “Catching Fire, How Cooking Made us Human” (Basic Books, New York, 2009) Richard Wrangham, the Ruth Moore Professor of Biological Anthropology at Harvard University writes,

A long delay between the adoption of a major new diet and resulting changes in anatomy is also unlikely. Studies of Galapagos finches by Peter and Rosemary Grant showed that during a year when finches experiences an intense food shortage caused by an extended drought, the birds that were best able to eat large and hard seeds – those birds with the largest beaks- survived best. The selection pressure against small-beaked birds was so intense that only 15 percent of birds survived and the species as a whole developed measurably larger beaks within a year. Correlations in beak size between parents and offspring showed that the changes were inherited. Beak size fell again after the food supply returned to normal, but it took about fifteen years for the genetic changes the drought had imposed to reverse. The Grants’ finches show that anatomy can evolve very quickly in response to dietary changes…Other data show that if an ecological change is permanent, the species also changes permanently, and again the transition is fast…The adaptive changes brought on by the adoption of cooking would surely have been rapid. (p. 93-94, emphasis added.) (See Book Reviews)

Behavior

September 26th, 2009

Understanding the gene-environment-behavior connections Implications of gene-behavior interactions: preven…[Obesity (Silver Spring). 2008] – PubMed Result

Some see eating as an automatic behavior over which individuals have less control than they think Eating as an automatic behavior. [Prev Chronic Dis. 2008] – PubMed Result

While controversial, the view of eating or hunger as an addiction has many interesting parallels with studies of addictive behavior The neurobiology of appetite: hunger as addiction. [Int J Obes (Lond). 2009] – PubMed Result

It is generally accepted that humans have a genetic predisposition to obesity which is fueled by our modern environments. However, not everyone is becoming obese. Why? Individual differences in the neurophysiology of r…[Int J Obes (Lond). 2009] – PubMed Result Obese-resistant individuals may sense changes in their energy intake more quickly than persons who are obese. The effects of overfeeding and propensity to weigh…[Physiol Behav. 2009] – PubMed Result

Obese individuals may have evolved weak mechanism which favor overeating. Control of food intake in the obese. [Obes Res. 2001] – PubMed Result High concern over food intake may, paradoxically, lead to higher intake Determinants of food choice: relationships with ob…[Obes Res. 2001] – PubMed Result

Stringent parental controls may also disrupt a child’s development of internal cues for controlling eating. Development of eating behaviors among children and…[Pediatrics. 1998] – PubMed Result