Lessons from the Amish
If we believe news reports this week, there’s no excuse for being fat because our genes can be overcome by having a healthy lifestyle and getting plenty of exercise. A new study of Old Order Amish living in Lancaster, Pennsylvania, was reported as showing that physical activity can combat obesity and keep people trim, even among those with a genetic susceptibility to obesity. Today’s modern lifestyles and obesogenic environment, with its perceived more fattening, processed foods and lack of exercise, are believed to cause the current obesity epidemic. And people living simpler lives, eschewing the trappings of modern life, eating natural foods and getting lots of exercise, don't have weight problems...or so the myth goes...
A study just published in the Archives of Internal Medicine, led by Evadnie Rampersaud, MSPH, Ph.D., and colleagues while at the University of Maryland, was a secondary analysis of data from the Heredity and Phenotype Intervention (HAPI) Heart Study.
The HAPI study, begun in 2003, involved four-short-term interventions (effects on platelets after 2 weeks on aspirin, effect on brachial artery after 2 ½ minutes of hand and wrist submerged in ice water, effect on brachial artery 1-6 hours after eating a high-fat milk shake, and blood pressure and urinalysis after 6 days of a high salt diet followed by a low-salt diet) among 868 participants of the Amish Family Calcification Study, an ongoing study of osteoporosis and heart disease among Old Order Amish. Participants had DNA blood tests and had undergone a wide range of physiological tests, including a 7-day measurement of physical activity by accelerometry.
For this study, Rampersaud and colleagues used the database on 704 healthy Old Order Amish adults from the HAPI study, average age of 43.6, for whom 92 single-nucleotide polymorphisms (SNPs) among the obesity-related (FTO) gene variants had been genotyped. At least one variation of this gene is prominent among those of European descent, including the Old Order Amish. To look for correlations between the expression of these obesity-related gene variants and levels of physical activity, they constructed a regression model and assessed the odds ratios of any interactions compared to the full cohort.
Despite the great import being given this study’s findings as a prescription for weight management, a prudent precaution is to remember that it was an epidemiological data dredge study. Anytime we throw enough variables into a computer, it’s bound to find some correlations, but that doesn’t mean they mean anything. This study is no different.
Findings. Among all of these obesity-related genotypes, they found no statistical links to actual BMIs. Only with the A allele for ‘rs1861868’ was there an association with being obese or overweight (26% and 15% odds ratio, respectively), but neither odds ratio is tenable (above random chance or modeling error) for a computer-derived correlation. They next looked at “the relationship of ‘rs1861868’ with BMI and obesity, stratified according to physical activity level.” Among the Amish with this particular gene variation, however, they found no statistical correlation to BMI associated among those with the highest levels of physical activity. Only a 28% higher odds ratio (also untenable) between the genotype and obesity was seen among those in the lowest level of physical activity.
Adding further caution to the significance of this correlation, the authors said:
When men and women were evaluated separately without consideration of covariate [like age], the association of rs1861868 genotype [with exercise] reached nominal statistical significance in women only, not in men. However, there was no evidence that the effect of genotype on BMI differed substantially between men and women, particularly when the level of physical activity was included in the regression model (ie, the genotype by sex interaction term was not statistically significant; P =.17).
The authors added that the function of this gene variation is not understood. Unlike many of the news headlines, there is no single obesity gene. More than 600 different genes, markers and chromosomal regions have been linked so far to the human obesity phenotypes through the Human Obesity Gene Map project and science is a long way from sorting out their true clinical relevances and interrelationships. Co-author, Dr. Soren Snitker told the media that obesity is much too complex to attribute to exercise or the FTO gene alone.
In the published paper, though, the authors concluded: “These findings emphasize the important role of physical activity in public health efforts to combat obesity, particularly in genetically susceptible individuals.”
While it’s politically correct to promote exercise to combat obesity, it’s not reality, as this study showed.
Time for a reality check
Definitions are everything. With any claim, first and foremost, we must understand how a word is being defined. In this case, what this study considered high and low levels of “physical activity” were far different from what most people might consider such distinctions.
The reality of physical activity as having any significant correlation to obesity was actually not supported in this study. The level of physical activity in the two strata used by the authors was defined as the energy expended at the 25th and 75th centiles of all of the Old Order Amish in this study cohort:
For women, energy expenditure was 2,610 and 3,590 kcal/d at the 25th and 75th centiles, respectively, whereas for men energy expenditure was 3,130 and 3,990 kcal/d at the same centiles. Thus, in this population, a mean activity level of 860 calories for women and 980 calories for men separates the high- and low-activity strata, which differ in their phenotypic expression of the at-risk FTO genotypes.
In other words, there was no correlation among the Amish with this gene variant and BMIs among the women working out as much as about 10 hours a day and among men 12 hours a day!* Only when they were physically active pretty much every waking hour of the day — 14 hours/day for women and 16 hours/day for men — was a correlation [albeit untenable] with a 2.1 units lower average BMI reported:
We found that SNP associations with BMI and related measures were limited to less physically active individuals. In the less active group, being AA homozygous for the rs1861868 FTO variant was associated with an increase in BMI of 2.1, a slightly higher estimate than that obtained by Frayling et al... By contrast, in the more physically active [Old Order Amish] stratum, the associations of the FTO variants were much smaller and not statistically significant.
Assuming, for a moment, that the correlation is real, for a man of average Old Order Amish height and BMI, working out 16 hours versus 12 hours a day would equate to about a 15 pounds difference; and for a woman, working out 14 versus 10 hours a day would correlate with a whole 12 pounds difference in body weight. These nominal weight differences would still not transform someone naturally obese into someone thin. Similarly, even these weight changes seen among the least active Amish in this cohort compared with the most active, didn’t raise their mean BMIs into the obese category.
Most people cannot afford to, nor would most want to, devote 14-16 hours a day to exercise in order to be one dress size smaller. They have other priorities. These daily exercise levels in this study population are so unrealistic, likely even among contemporary Amish in other regions, they don’t credibly explain the wide natural diversity of body sizes among people today.
The most accurate interpretation of this study might have said, instead: Most genetically-predisposed healthy fat people will still be fat, even working out every waking hour of the day!
Yes, even with these exhaustive levels of physical activity, most Amish adults are just as fat as the rest of us.
The myth of an obesogenic environment and thin Old Order Amish
It’s one of the most popular contemporary myths — and the foundation of present-day obesity public policies — that if we all lived rural lifestyles and did hard physical labor all day; ate homegrown, homecooked foods; and had none of today’s modern conveniences and electronics, we would all be thin. It’s a nostalgic vision of past eras ... but it’s not true.
Even living these idealized lifestyles, eating virtuously and physically active far beyond what most of us could imagine, the Old Order Amish are just as fat as the rest of the United States white population. In fact, the average BMIs of mature Amish women (over age 40) are 1-2 kg/m2 higher than those of other U.S. women the same age.
As researchers, led by Dr. Wen-Chi Hsueh at the Southwest Foundation of Biomedical Research in San Antonio, Texas, recently reported in the Journal of Clinical Endocrinology & Metabolism, obesity is just as heritable among the Amish as other populations. These researchers had genotyped 672 Amish for 357 genetic markers in 22 autosomes and found that the specific genes that contribute to human obesity are unknown. They were unable to detect any significant linkage for any of the traits they analyzed, even in this homogeneous population -- perhaps, they said, because of the complexity of genetic mechanisms and subtle effects of individual genes even in this relatively homogeneous population.
The semi-cloistered members of the Old Order Amish of Lancaster County, Pennsylvania, can trace their ancestry back 14 generations to when their ancestors immigrated from German and Switzerland in the 18th century. Dr. Petra Platte of the University of Trier in Germany extensively researched the Old Order Amish and found that they are probably the most homogeneous group of people in the world for studying the genetics of obesity. They’ve lived in amazing genetic isolation, only marrying within their community, have large families and share the same socio-economic status, diets and lifestyles. Dr. Platte also reported that they eat their traditional foods that include eggs, meats, pasta, fatty sauces, sweets and cakes on a daily basis. The Amish don’t diet and the ideal of slimness is foreign to them, according to the German researcher. Stoutness and robustness is considered an asset for hard field work among the men and childbearing for the women. Yet, the Amish have lower rates of heart disease and rates of type 2 diabetes that are only about half that of the general American population.
Dr. Platte’s work was reported by the Deutsche Forschungsgemeinschaft (DFG), the central administrative body of science and publicly funded research in Germany. After recording the weights of some 3,000 Amish people in 17 extended families, Dr. Platte and colleagues examined the heredity of obesity and found fat Amish have fat children and fat siblings. Obesity was predominately inherited among them, too. And, the Amish of Lancaster become obese just as frequently as other Germans, even though they are, on average, much more physically active.
This is also what the University of Maryland researchers reported this week. Among the Old Order Amish, the adult women had an average BMI of 27.8 — about 162 pounds for a 5’-4” woman — and the men had average BMIs of 25.7 — about 180 pounds for a 5’-10” man. “The prevalence of overweight and obesity in [Amish] men was 54.0% and 10.1%, respectively, and in [Amish] women was 63.7% and 30.5%, respectively.” They are not thinner than the rest of country, despite untold amounts of physical activity and healthy living.
So, all of those news stories claiming “Amish people show us how to avoid obesity,” "Amish thwart obesity gene with physical activity," “Amish keep slim despite having obesity gene,” “Active Amish put obese Americans to shame,” “Exercise Combats Obesity Gene,” and “Grandma was right...hard work will keep us from getting fat,” were clearly written by people who hadn’t read the study and just assumed that exercise and living well must lead to thinness.
As with so many popular beliefs, the evidence is often just the opposite. Even enormous amounts of exercise still won’t make naturally fat people thin. Maybe the most valuable lessons that the Amish can help us understand about health and happiness have nothing to do with weight at all.
© 2008 Sandy Szwarc
* By the author’s calculations, 3-4 hours of moderate-intense physical activity burns about 900 kilocalories.