SNPwatch: Apple or Pear? How Genes Help Shape Your Shape

You’ve probably heard about the fruit-based analogies to describe body shape. “Apples” tend to carry more weight around their waist whereas “pears” tend to be heavier around the hips and thighs. But the differences between apples and pears extend beyond simple appearance. Studies have shown that physical shape, primarily where you carry your excess weight, can have a profound impact on your overall health. Bad news for the apples … people who are rounder around the middle appear to be at greater risk for developing heart disease and type 2 diabetes than their pear-counterparts.So, which fruit are you? One way to determine your body fat distribution pattern is to calculate your waist-hip ratio (WHR) by dividing the distance around your waist (measured just above the belly button) by the distance around your hips (measured at the widest part). A WHR over 0.8 for women or 0.95 for men is considered high and categorized as a risk factor for metabolic disease.In a recent publication from Nature Genetics, a team of scientists from the Genetic Investigation of Anthropometric Traits (GIANT) report their findings from a two-phase study into how genetics influence waist and hip size. This investigation, including nearly 200,000 people of European descent drawn from more than 50 studies, is one of the largest genetic studies ever carried out for any trait. Following an impressive data analysis effort, authors announced the identification of 14 SNPs (13 new and one previously reported) associated with body fat distribution.In addition to exciting new SNP discoveries, results from this study suggest that genetics play a more significant role in determining body fat distribution in women than in men. In women, not only do more of the SNPs associate with WHR (12 of 14 SNPs compared to three of 14 SNPs in men), but they also appear to have greater influence on waist and hip size.The study authors also hint at potential associations between the 14 SNPs identified in their research and common risk factors for heart disease and type 2 diabetes. For example, the T version of showed strong associations with elevated triglycerides and insulin resistance. The risky versions of , ( in the 23andMe database*), and also demonstrate significant association with type 2 diabetes.As with obesity and many other conditions with a strong environmental component, genes only account for a small piece of the puzzle underlying variability in body fat distribution.  Even so, this study establishes an important observation: the SNPs associated with body fat distribution (measured by WHR) appear to be mostly distinct from those SNPs associated with overall body fat content (measured by body mass index (BMI)). Since the location of body fat plays a pivotal role in disease risk, a better understanding of the genetic risk factors underlying increased waist and hip size may lead to improved therapies or lifestyle recommendations.SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.
  • Puff Daddy

    “As with obesity and many other conditions with a strong environmental component, genes only account for a *small piece* [emphasis mine] of the puzzle….”

    Why are you using the weasel phrase “small piece” when you state elsewhere on 23&me that “The heritability of obesity, as defined by having a body mass index of 30 or more, is estimated to be 64-84%”

    64-84% doesn’t seem like a “small piece” to me — at least as far as BMI is concerned, and it seems like you have chosen to muddy the waters with purposely vague phrasing so as to not offend. Why is that?

  • KimB

    Thank you for the comment. What I meant by “genes only account for a small piece of the puzzle” is that obesity, as with many complex morphological traits (such as body size, height, etc.), does not have one single gene (or a few genes) with a large effect but instead has many genes that each play a small role in the variation. Thus, the SNPs reported in this study will contribute to waist-hip ratio but will each only play a small role in overall body fat distribution. Also, note that the heritability of WHR is 30-60%, compared to the estimated higher heritability of BMI.

    Heritability is actually a tricky concept in that it has a very narrow definition but is often broadly applied and misinterpreted. A heritability estimate applies to populations rather than individuals, and is a measure of how much of the differences between individuals for a trait is attributable to genetics. It does not describe how much genetics determines individual manifestation of a trait. Heritability can change over time and can also be affected by environmental factors, making it very difficult to understand, measure, and interpret!

  • Glenn Hammonds

    Is there a way to get a report for my genotype for all the SNPs mentioned in the table? All at one time, rather than one at a time.

    I haven’t found a way to submit more than one SNP at a time, and it is quite frustrating, as this should be reasonably easy to set up on your end. For instance, when I put a list of SNPs into the “Browse Raw Data” field, it returns results for the first one only. Why not for several at once?

    I suppose I’ve simply not found the right way to do it – enlighten me.

    • Hi Glenn,

      There is no way to retrieve raw data for multiple SNPs currently, but we are constantly improving the product so it’s possible we’ll work on it at some point. As you say, it may be relatively simple, but there are hundreds of such improvements we could make (as well as lots of less simple ones) and very limited resources, so it’s a constant battle to prioritize which ones to do at any given time!

  • Hi Glenn,

    I just got my result, and have been browsing the Spittoon with a Firefox plugin that makes it much easier to see your personal genotypes. Hope it helps you!