So, I’ve covered a couple of things before about obesity; specifically watching Dr Giles Yeo and leptin. If you don’t know type 2 diabetes is kinda my jam, and obviously obesity can play a big role in causing type 2 diabetes. So obviously I was interested in this article stating that a modern lifestyle is to blame for making y’all chubby.
I’ve covered before (in those links above) that your genes play a massive role in if you put on weight. But Dr Yeo compared them to poker. “You can win with a bad hand, and you can definitely lose with a good hand.” And this study seems to show that especially.
Basically the incidence of the mutated genes isn’t increasing. So why are we getting fatter?
Walter and folks looked at the genes of almost 9000 patients born between 1900 and 1958. They compared 29 mutations, which have been linked to obesity, to generate a Genetic Risk Score (GRS) combining all changes. I won’t go into too much info, as it uses very complicated maths. Basically mutations can take away or add to the risk of obesity, so the GRS is a sum of the positive and negative influences. Get it?
The first cohort of subjects were the oldest, so basically people born before we began feasting for every meal. Interestingly, here was no significant connection between the GRS and the BMI of people. Even though the incidence of mutations and the value of the GRS was the same as for people born later, for some reason people didn’t get fat. As you work your way through the cohorts, looking at people born later, the association increases. This means that the GRS starts to mean more as you get younger patients. Also, the older people got the more likely they were to be obese, potentially due to the increased availability of high-calorie foods, and the sedentary lifestyle old folks tend to have.
This suggests that the modern environment plays a bigger role in whether or not you develop obesity. So, what’s the happy haps?
The authors suggest a few things. The average calorie intake in the States has increased by a whopping 22% (in woman; only 7% in men – still bad though). Sugar-sweetened drinks increase the risk hugely, and consumption of these bad boys has increased rapidly. I’ve just watched a live cast from Physiology 2016, where Prof John Blundell showed that when given a choice people choose energetically dense food.And now we live in a time when folks can access calorific food simply, and cheaply. Another reason may be because we’ve gotten lazy. Although Prof Blundell mentioned that even exercise cannot undo a high calorie diet. Demereth et al carried out a similar study, but had a more complicated explanation; epigenetics!
I have talked about epigenetics before, but probably in real life rather than here as it’s a bit of a head scratcher. Simply put your DNA contains all the data needed to make you. However, to stop DNA from just being accessed all of the time you need something to control it. This can involve modifying the DNA directly, usually by sticking something onto it. This can increase or decrease the rate of which genes are transcribed (i.e. made) (kind of…). Crucially epigenetics don’t actually change the DNA, just the way it is read. And obesity can cause quite a few epigenetic changes. This means that the expression of the proteins involved in obesity and other nasty things can be changed, simply by becoming obese. It’s like an ironic* perpetual motion machine.
Think of your DNA like a fancy library, like one with a museum. All of the day-to-day books for children and idiots are accessible all the time. But those old, fragile books are kept under lock and key, and can only be used in a controlled environment. Now the easiest way to get access to the books is to bribe the librarian with a pile of greasy donuts. Most of the time anyway; perhaps sometimes the librarian shuns your treats and tells you to do one.
Now imagine your big fat grandad has gone around opening and locking doors and eaten the keys. That’s right, epigenetic changes can pass from one generation to the next. Someone at ENDO 2015 said it can pass over two generations, but I can’t remember who, so let’s just let that hang there…
(Since I originally wrote this piece, this came out. The study shows that incidence of Type 2 Diabetes is increasing, and that the percentage of younger people getting the disease is increasing. If you don’t know, obesity and Type 2 Diabetes usually go hand in hand.)
*American ironic. Not proper ironic
Today’s quote is from Stephen King.