New View on the Origins of Our Obesity Predicament

December 24th, 2011 No comments »

As readers know, there is a certain disconnect about when the obesity    epidemic began. Personally, I am quite persuaded that the historical record for the increase in human weight and height (the two parts of the BMI formula) goes back at least 350 years. (See, The Techno-physiological Revolution). On the other hand, something seemed to happened in the United States around the 1970s to send the rates skyward. There are no end of theories, all of which have some plausibility. So now comes Melinda Sothern, a well-respected and highly published obesity researcher, with a new look at mothers in the 1950’s. (Ouch! That’s a little close to home.) Her thoughts in this article do meet up with current research on genetic and, especially, epigenetic factors influencing the development of obesity. 

Many knowledgeable researchers have avoided going into this territory, not because of the science but because of the fear of being blamed for blaming mothers. This is not an inconsequential factor as parents may defer medical care for fear of being blamed for their child’s weight problems. (See the Cleveland obese boy incident.)

Sothern’s experiences and scientific credibility gives impetus to seriously consider her thoughts on the origin of our current predicament, given in this article in The Republic, ’50s women may have triggered obesity epidemic | The Republic

Genetics and Treatments

December 20th, 2011 No comments »

The Diabetes Prevention Program (DPP) is regarded as a hallmark of behavioral intervention in the treatment of adult obesity. Now comes a paper from the DPP Study Group, as well as drug therapy via metformin. It recognizes that genetic factors affect the success of participants in achieving and maintain weight loss. Genetic Predictors of Weight Loss and Weight R… [Diabetes Care. 2011] – PubMed – NCBI

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

October 5th, 2011 No comments »

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

Are Persons with Obesity Different?

September 27th, 2011 No comments »

Are persons with obesity different? The question is fraught with implications. Much of obesity policy is premised on the assumption that persons with obesity are just like normal weight persons but with less self-control. The assumption is that education and awareness will overcome their lack of awareness and result in more self-control, just like normal weight persons. Of course, a genetic basis for obesity is counter to this assumption. How does this genetic pre-disposition express itself? Two recent studies may provide insights. In one, overweight persons show a higher capacity for storing fats but a lower capacity for ridding themselves of them, using the radioactive isotope carbon-14. Cell dysfunction linked to obesity and metabolic disorders | ScienceBlog.com

 In another study, the brains of persons with obesity were found to create a greater desire for high-calorie foods than normal-weight subjects which would explain why people who become overweight tend to remain overweight. Study: Obese people’s brains may crave high-calorie foods – USATODAY.com

New Insight on Gene-Environment Interaction

July 9th, 2011 No comments »

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

U.K. Aims at Fetal Programming To Fight Obesity

July 4th, 2011 No comments »

The United Kingdom has launched the first trial of an effort to affect the intrauterine environment and thus the development of childhood obesity in the womb. The trial is sure to be controversial but it is certainly consistent with recent scientific findings. See Programming a Fetus for a Healthier Life – WSJ.com

More Disease and Death Ahead. It’s Going to Get Ugly

July 4th, 2011 No comments »

Editor:  This is a really important paper.

Forecasting the future effects of obesity has been a complicated business. One reason is that just measuring a current trend and then projecting it into the future (called the ‘two-dimensional model”) does not incorporate the changes occurring now to younger persons which will not become manifest until much further into the future.  Two examples are exposure by children to second-hand  tobacco smoke and childhood or adolescent obesity.  Underforecasting the effects of an epidemic like obesity can lead policy makers to pay insufficient attention or devote inadequate resources or direct those resources in unproductive ways. Unfortunately, it seems all of those poor outcomes are occurring.

So another method, the “three-dimensional” model has been developed to take future changes into effects. It is not a pretty picture.  The authors of a new paper in Health Affairs, Eric N Reiter, S. Jay Olshansky and Yang Yang, write, “We have shown that a reversal in US life expectancy rates is a distinct possibility in the long term, and a high probability in the short term for subgroups of the population most affected by obesity.” They note that childhood and adolescent obesity will predict the metabolic syndrome in many, as well as type 2 diabetes. After reviewing the evidence on the inter-generational inheritance process of transmission of obesity, they warn, “For example, fetal overnutrition has been shown to permanently increase appetite and shift preferences toward junk food among offspring, increasing the risk of obesity. Both human and animal studies indicate that maternal and paternal health behaviors – such as diet and smoking – affect the probability of obesity and related metabolic programming. In other words, a child’s metabolism and risk for certain diseases later in life can be “programmed” by conditions that existed during gestation. ..The implications of this body of science are profound: the high prevalence of obesity observed among younger people today is likely to be transmitted to future generations – regardless of the health behaviors of children yet to be born.” (Emphasis added.) So, this paper indicates we are underestimating the impact of childhood and adolescent obesity. See New Forecasting Methodology Indicates More Disease And Earlier Mortality Ahead For Today’s Younger Americans

The TechnoPhysio Evolution

June 8th, 2011 No comments »

Book Review:    The Technophysio Evolution    

The Changing Body, Health, Nutrition, and Human Development in the Western World since 1700

 by Roderick Floud, Robert W. Fogel, Bernard Harris and Sok Chul Hong, (Cambridge Press, 2011)

The authors are distinguished economists (Fogel has a Nobel Prize in Economics). With dizzying detail, it traces the changes in the human body over the last 300 years in Britain, France and the United States. During this period, humans have become much taller and heavier than ever before. The book charts the “technophysio evolution,” a complex interplay between increasing technological changes and improved standards of living, resulting in improved nutrition. The improved nutrition is passed from mother to child to child with improvements in height and weight in successive generations. This is not a straight line but the trends are unmistakable – improved mortality with tall and heavier adults.

The Technophysio Evolution hypothesis has three elements:

  1. The nutritional status of a generation – shown by the size and shape of their bodies – determines how long that generation will live and how much work its members will be able to do.
  2. The work of a generation, measured both in hours, days, and weeks of work and in work intensity, when combined with the available technology, determines the output of that generation in terms of goods and services.
  3. The output of a generation is partly determined by its inheritance from past generations; it also determines its standard of living and its distribution of income and wealth, together with the investment it makes in technology.
  4. The standard of living of a generation determines, through its fertility and distribution of income and wealth, the nutritional status of the next generation.
  5. And so on, ad infinitum.

In other words, increasing body weight is a by-product of advances in wealth and income, producing healthier, i.e. larger children, who, in turn, produce better nourished, i.e., larger,  children.

The “techno” part of this evolution include everything from American colonists moving from a wooden plow to an iron one; improvements in food production and distribution, refrigeration, canning, changes in water, sanitation and public health which reduced mortality from infectious diseases while improving nutrition for more and more people.

The “physio” part incorporates research on the fetal origins of adult disease and will support the attention to epigenetics as an important aspect in the development of obesity. This is not purely genetics or genetic determinism but the process of transition of improvements in nutrition to the health of the mother and her survival as well as to the survival of more children for longer periods of time. Epigenetic changes is coming into focus as a critical stages for the development of obesity and will certainly receive more attention in the future. Epigenetic changes in early life and future risk o… [Int J Obes (Lond). 2010] – PubMed result

Is there an end to the process or is there a natural limit to this growth? Well, we don’t really know but none appears so far. (It seems to me, at least, that evolution has not felt it necessary to provide unlimited height of the species since there does not appear any survival value to being taller. On the other hand, nature has felt that there was a distinct survival value to being able to store energy (read fat) on our bodies and there does not seem to be a particular limit to this.)

by permission, Cambridge University Press

 

Interestingly, the authors find that, for American white males ages 40-59, the increase in BMI from 1870 to 1980 is less closely related to food consumption than to reduction of contaminated environments and work hours. “Not only have working hours,” they write, “declined substantially throughout the twentieth century, but the type of work became more sedentary, and so required less energy.” However, “The recent large increase of BMI in 1980-2000 (6 percent) is highly connected to increased food intake during the period (22 percent). (At p. 336) Further, they note the average BMI of American white males has increased by 15.7% throughout the 20th Century, half during the last two decades of the twentieth century. “This means that American body size is rapidly moving toward overweight and obesity.This would seem compatible with a new finding from Tim Church and colleagues at the Pennington Biomedical Research Center that in the 1960’s about half of jobs in private industry required at least moderate physical activity. That figure is now less than 20%. Over the last 50 years, occupational daily energy expenditure decreased from by 142 calories in men and a similar amount in women.  Trends over 5 Decades in U.S. Occupation-Related P… [PLoS One. 2011] – PubMed result

What are the policy implications of this Technophysio Evolution?

First, increases in body size are a product of 300 years improvement in technology, productivity and standards of living. This evolution began long before television, fast food, vending machines, sugar-sweetened beverages and other would-be villans in the obesity epidemic.

Second, the very same nutritional improvements which led to larger bodies in Europe and the United States are being actively pursued in undernourished parts of developed nations and throughout the developing world. This indicates greater and greater levels of obesity in the developing world with obesity related diseases.

Third, epigenetics needs to receive more attention as a point of intervention in the development of obesity.

Fourth, simplistic views that blame individuals and proclaim that just cutting back food  or going to the gym will fix the obesity epidemic.  Strategies which just repeat the ELEM mantra (Eat Less Exercise More) have to be questioned if those strategies are likely to affect this profound historical trend.

A few years ago, Gina Kolata, in her book, Rethinking Thin (Farrar,Straus and Giroux, 2007)  discussed the views of some obesity researchers that we are looking at a new stage in the evolution of the species. This tome adds significant evidence that our obesity strategies need to be re-thought to take this 300 year trend into account.