23andMe’s genotyping results has provided scientific support for something I’ve been telling people over the years without many believing me… that I can become fat. At 5’2″ and 108 lbs. of a marathon runner’s body, I can’t say I blame them. I don’t look like much at this weight, never mind the 90 lbs. I used to be at before I started distance running 16 years ago. Yet, I can eat a lot, with consequences almost like any over typical person if I don’t run it all off.
The Anecdotal Case
It did not take me long to put on 8 lbs., or 7% of my body weight, one winter when I exchanged marathon training for the much less energy demanding long track skating on an outdoor oval the first year we had it in Halifax. I really did have to watch what I was eating if I didn’t want that number to keep increasing. It was far from obesity given my starting point, but it was gathering in the gut and I wasn’t going to be looking pretty if I just kept on eating and drinking what I normally did during marathon training.
The way I’ve always tried to make my case about being able to get fat was to point to the Vietnamese living in America. Vietnamese in Canada aren’t too different, but the American fast food culture definitely has a bigger impact on the lifestyles of Vietnamese living in America, in my opinion. Often, if you looked at their family photos, they don’t look like the family photos you’d see of Vietnamese families living in Vietnam. The American ones are definitely fatter, and I mean fatter rather than average compared to malnourished Vietnamese! This is a broad sweeping statement, of course. There are tons of healthy Vietnamese around in North America. However, I would say it is true.
The better case would be with the first generation Vietnamese Americans, who mostly grew up with plenty of food, and not the greatest food like fast food, even when great Vietnamese food was available at home or at many cheap Vietnamese restaurants in American cities. If I lived in America, I’d probably never eat McDonald’s unless I wanted to hang out and meet American girls, which I suspect probably has something to do with why the Vietnamese kids there hang out at such places when cheaper and better home cooking cuisine are just as readily available to them on many days. Looking at pictures of these kids and how many of them are overweight is sometimes shocking to me!
So the obvious question I pose was why should I expect to be any different? These kids and adults would have pretty much similar genetic make-up to myself, being Vietnamese. Sure there are fine differences that 23andMe points out, rather interestingly, but we’re pretty similar and would be grouped all together by 23andMe as of East Asian ancestry.
The Genetic Case
The risk for obesity (BMI 30 or greater), is 64-84% inherited, with the rest being what we can do to bring it on, like lots of bad eating. This is about risk of getting fat and having all kinds of problems with it, like diabetes, that is hard to get rid of, rather than just getting fat. You might have a low risk for obesity but drink a couple of litres of pop a day and see how long before you start getting really sick for the long term!
The results from 23andMe on the rs3751812 gene is only available for those of Europeans descent, and inconclusive on Asians and Africans. It’s not the ultimate proof, but if I were European, I’d have a 0.85X risk of becoming obese compared to the typical European.
In six other studies cited by 23andMe, again for Europeans, eight genes were identified in several hundred of thousand of people to have an influential factor on Body Mass Index (BMI). They are listed at the end. Of these, I only had the right combinations for a genetic influence of 1.24 BMI point reduction. That is, without it, my BMI would be 21 rather than 19.8. That’s well in the healthy range of 18.5 to 25 rather than on the lower end as I am. This is the result for Europeans, but the results for Asians should not be significantly different when you look at the value range of influence here. So what if it might be 1 or 1.5 BMI points? It’s a 0.25 point difference out of 18-25. Same outcome.
Further, my genotype at one gene influences the reduction of my waistline by all of 0.9 centimeters or about 3/8 of an inch. Ooooh. (sarcastically)
On the other hand, for what genetic variations contributes to BMI, it is a mere 0.46 BMI (2.52 lbs). Variations is the key word here. What this means is that a close clone to me, with variations among just six other genes (out of almost a million tested), who lived the same lifestyle, would only be 2.52 lbs lighter at most!
So yes, like you, I do have to watch what I eat and drink. I do have to moderate it. And if I want to have less impact in eating and drinking what I want when I want, I had better be keeping up the marathon training or something as intensive!
Genes Which Influences BMI
|RSID||My Genotype||Result, Potential|
|rs6548238||CC||Typical BMI, +/-0.52 BMI points|
|rs925946||GG||-0.35 BMI points, +0.35 points|
|rs7138803||GG||-0.41 BMI points, +0.41 points|
|rs9939609||TT||-0.33 BMI points, +0.33 points|
|rs13130484||CT||Typical BMI, +/-0.19 BMI points|
|rs4788102||GG||-0.15 BMI points, +0.15 points|
|rs10838738||AG||Typical BMI, +/-0.07 BMI points|
|rs10871777||AA||Typical BMI, +0.22 or 0.44 BMI points|
Genes Which’s Variation Adds to BMI
|rs3751812||GG||0.33 BMI points for each T|
|rs10871777||AA||0.2 BMI points for each G|
|rs13130484||CT||0.19 BMI points for each T|
|rs4788102||GG||0.15 BMI points for each A|
|rs10838738||AG||0.07 BMI points for each G|
|rs3101336||CC||0.1 BMI points for each C|