Genetics and Obesity. Why Your Genes Drive Your Behaviors.

The genetics of obesity.

Recently I have been tagged in a lot of videos from people disregarding the role that genes have when it comes to your body weight.

They often use false dichotomies, like 'no, it is not your genes, you are eating too much' which grossly misrepresents the role that genes play.

It isn't your genes *or* how much you eat, it is more like *how* your genes influence how much you eat.

So, let's talk about some basic genetic concepts and how they are involved with body weight regulation.

References:
- The body-mass index of twins who have been reared apart
- A twin study of human obesity
- New advances in the genetics of early onset obesity
- Positional cloning of the mouse obese gene and its human homologue
- Congenital leptin deficiency is associated with severe early-onset obesity in humans
- Lessons from extreme human obesity: monogenic disorders
- The genetics of obesity: from discovery to biology
- Variability in the heritability of body mass index: a systematic review and meta-regression

[fkrbueh]

The elephant in the room is appetite. This was brought home to me when the person who had a gastric sleeve operation said it wasn't the fact that my stomach is smaller that I eat less it's because of taking away the hormones that regulate my appetite, and I no longer desire food. For myself I have a big appetite and I really struggle to keep my weight down. My mother had a similar problem. Yet my father who didn't have a big appetite rarely thought about food unless he was really hungry. Professor Roy Taylor at Newcastle University, said that if you've got a big appetite, you've got a big problem. 
In my book, you don't have to have Prada Willi syndrome to have problem with overeating owing to a big appetite. I think you'll understand what I mean.

[pradlark]

To me the conversation about how there's many factors in muscle building, fat loss etc really reminds me of the concept of privelege and how most REALLY don't get it and take the idea of it being brought up as saying that their achievements are nothing because it wasn't as hard for them, which is NOT the aim, the goal is to get people to understand empathise and support people with different starting points, dreams and struggles, that's all, jesus i'm so sick of misinformation that makes most people take the complete wrong idea about something and then massively bias them to the point they will never clarify their misunderstandings because they don't know they're just lacking some nuance!

I love your vids Ben :)

[kristencroft]

Thank you for addressing this. There is obesity in both my parents families, and it’s something I hav struggled with my entire life—first diet at 7 mos old. I was diagnosed with Leptin Receptor Deficiency about 4 years ago. It answered so many questions, but I’ve already lived a lifetime being told I lack self-control and that I need to try harder to lose weight. Changing the psychological patterns is really hard. In the past no matter what I did I continued to gain weight.

I’m currently on a medication to treat LEPR deficiency, and I did lose a good chunk of weight initially, which was shocking to me. But the other benefits have been life-changing—I now experience satiety, and I’m not constrained getting signals that I’m starving, and I actually have the energy to move and exercise and no longer have to spend every weekend sleeping.

[blurjose]

Thank you for validating the experiences of many of us. It angers me when people say it's an excuse and I don't work hard enough because I work hard, efficiently and consistently. I'm strong and my blood panels indicate good overall health but still my doctor mentions the BMI. On occasion---as silly as this sounds--I want to say: I can bench press 315lbs a handful of times with good form. I walk 7 miles four days a week without issue. Why don't you ask me about my workout habits and the ways I do eat healthily?!

[crisstoff]

It makes sense in way, in times of food being scarce or having to hunt or grow, it mean that it wasnt available whenever you wanted and having a big appetite would mean you had extra energy to last another day because who knows when is your last meal, so ironic in that way its perfect for survival but now we have too much food at our finger tips, it now becomes a fight with your urges.

[jennh]

It all goes back to the nature/nurture idea. It's part genetics and part life choices, and it may be harder for some than it is for others, just like everything else

[ETBrooD]

Genetics explain over 40% of BMR (base metabolic rate) differences among humans. I'm not exaggerating.

[dreambrush]

thank you! I feel like certain people really love to put the cico to everything and completely dismiss the genetics and life circumstances. I put in daily cardio, i walk to everywhere to get groceries and do errands (which luckily are within 15-20 walking distance), doing intermittent fasting and low carb diet and was basically either gaining weight slowly or maintaining (I'm slightly overweight). Nowadays I also added counting calories because I got kinda frustrated with not losing anything so now it helps, even if it's slow weight loss. It's also the fact that life happens and you can gain a lot back (eg. work stress, grief, anxiety) making it difficult to stick to cico and your body just signals to your brain to constantly to eat, even when you don't have to and already used to high protein diet. It's really hard honestly and I wish the fitness community wasn't so dismissive.

[mygetawayart]

People who claim obesity has nothing to do with genetics might aswell be evolution-deniers, because that's what they're doing: they're denying the genetic factors that led certain bloodlines to evolve to survive famine and scarcity better. If you're obese there's a very high chance that your parents also suffer from the disease and there's the chance your grandparents, while maybe not obese, were at least robust. Both of my parents do gain fat easily and have to struggle a lot to lose even a bit of weight. Both me and my sister, plus many of our blood relatives are or were obese.

That being said, to claim that behaviour & environment have nothing to do with it is just as much denialist as it is to deny the genetic component. To claim they're mutually exclusive is absolute bollocks.

[Enoch-Root]

Human genetics haven't changed radically since the 1970s when obesity was far more rare. Too many people use genetics as an excuse, far more than the amount of people who have genuine genetic issues which increase the likelihood of obesity.

In fact it makes no sense to speak of "a gene for.... ", as genes need to be understood in their environment.

[drno]

If we're talking science, let's see from the abstract of Lamiquiz-Moneo et al. (2019)

We genotyped 25 single nucleotide variants (SNVs) in 25 genes that were previously associated with obesity and calculated genetic scores that were derived from 25 SNVs. The genetic score was the variable that best explained the variations in weight from the baseline. The genetic score explained 2.4% of weight change variance at one year and 1.6% of weight change variance at the end of the follow-up period after adjusting for baseline weight, sex, age and years of follow-up.

So genetics explains weight variance 1.6% of the time.

The reality is that obesity rates haven't skyrocketed due to genetics, but lifestyle. People eat more, eat worse, exercise less and a lot of the time try to shift blame or even promote this way of life. We're living in an age where 'body positivity' means promoting and excusing obesity. Personal trainers have a right to be angry and it's ridiculous to suggest that they're angry at people having congenital leptin deficiency

[ETBrooD]

I have the opposite problem than overweight people. It's very easy for me to undereat and lose weight because I can go for many hours without food while feeling great. But this has sometimes led to bad eating habits when I finally pick up a meal, like not selecting healthy food, or eating too much in one meal.

[enigmatic]

Combine a large appetite with a natural tendency to store belly fat and you get someone who will never get six pack without being miserable 24/7.

[eternal_dread]

True, for me my body tends to be comfortable at 25% bf if I don’t diet/exercise, if I do I generally stay at 15-16% bf I also tend to gain muscle pretty easily I don’t follow any program I don’t count reps/sets even with a kinda low protein diet I gain muscle by pushing to failure/near failure

[zebobm]

@bencarpenter how common are these genetic disorders though? We have seen a huge increase of obesity rates in the West and Middle East/North Africa in the 20th century, it can't be because the rate of genetic disorders increased in the general population?

[Hat]

Blaming genetics is an easy way out to not take personal responsibility.

[Hopeful]

If I know at least one person you mean, and I think I do, I used to follow him but as time has gone on he's become far too weird in his take that he somehow knows health better than Drs and scientists. He doesn't.

[christophersmith]

Of course genetics plays a part….but it is only a “part”. But more importantly It’s about find the correct eating pattern and exercise that will help that person at that particular point in the life.
Also the realisation that being shredded may not be possible for that particular individual and just maintaining a healthy body weight and lifestyle is actually the goal.