Genes Hardly Matter in Health and Obesity

Some of your more hard-core genetic determinists assert that genes are very important for health and obesity, and that most of the variation between individuals is due to genetic differences.

That notion contains some truth, but with an important caveat: genes always interact with their environment. Genes can be responsible for differences in health and body mass index (BMI) only if the environment is the same between two individuals.

In obesity and health, the most important part of the environment is food.

Twin and adoption studies

Consider that both twin and adoption studies have “found that genetic factors had a strong effect on the variation of body mass index (BMI) at all ages”.1

Similarly, studies in twins have found that genes greatly influence the rate of death from coronary heart disease.2

So why do I say that genes hardly matter?

Rise of morbid obesity

Consider the following chart, which shows the rise in morbid obesity since 2000 3:

The percentage of people with a BMI greater than 50 rose 120%; those with a BMI greater than 40 rose 100%.

Could that be due to genes? I don’t think so. In fact, it’s impossible.

The environment these people live in changed. They ate more crap food and drank more sugary drinks.

A sudden drop in heart disease

Consider another chart, which shows what happened to the rate of heart disease deaths in Norway during World War II.4

Within the space of a couple of years, heart disease deaths dropped by around 20%. Why? The consumption of meat, milk, fruit, sugar, butter, and margarine all dropped — and calorie intake dropped by 20%.5 Fish consumption doubled.

Whether it was calories as a whole or a particular food category or changing macronutrient composition, we don’t know, although I’d point to fish, sugar, and less food all around. No doubt cigarette consumption dropped too, and people probably exercised more because they had to walk due to less gasoline.

But regardless of the cause(s), the point is, the environment changed, and this led to a drastic and immediate drop in heart disease deaths.

Genes are only important if the environment is the same

Genes can’t explain the rise in morbid obesity, nor the obesity epidemic as a whole. The environment changed.

Genes can’t explain the drop in heart disease deaths in Norway during WWII. The environment changed.

Using genes as an explanation is a counsel of despair. It says, don’t do anything, it’s your genes.

On the contrary, the environment matters a lot, both for individuals and society as a whole. To change your weight or your health, change your environment.

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  1.  Silventoinen, K., et al. “The genetic and environmental influences on childhood obesity: a systematic review of twin and adoption studies.”International journal of Obesity 34.1 (2010): 29-40.
  2.  Zdravkovic, S., et al. “Heritability of death from coronary heart disease: a 36‐year follow‐up of 20 966 Swedish twins.” Journal of internal medicine 252.3 (2002): 247-254.
  3. Sturm, Roland, and Aiko Hattori. “Morbid obesity rates continue to rise rapidly in the United States.” International Journal of Obesity 37.6 (2013): 889-891.
  4.  Strom A, Jensen RA. Mortality from Circulatory Diseases in Norway 1940-1945. The Lancet. 1951; 1(3): 126-129.
  5.  Angell-Andersen, E., et al. “The association between nutritional conditions during World War II and childhood anthropometric variables in the Nordic countries.” Annals of human biology 31.3 (2004): 342-355.

Leave a Comment:

Ben Richardson says August 5, 2016

Perhaps the post title should be *Human* Genes Hardly Matter . . . to distinguish these from the microbiota genes that can and do change rapidly and are hugely influential on health and obesity 😛

I do recommend looking into the work of Tim Spector, a geneticist and world leader of twin studies, therefore the significance of genes, who is now the leader of the British Gut Project and has refocused his studies from human genes to our microbes. Warning – fascinating stuff!

    P. D. Mangan says August 6, 2016

    Thanks, Ben I don’t think I was aware of Spector.

Belovar says August 6, 2016

Off topic.

It would be interesting to know what sites that you read and recommend about health, traning etc. Perhaps a “recommended sites” could be added to the front page?

Thanks for a good blog!

    P. D. Mangan says August 6, 2016

    Thanks, Belovar. I used to have a recommended sites feature but my site redesign disappeared it. I tend to try to read original research, but sites I trust are Dr. Steve Parker, George Henderson, Paul Jaminet, Dr. Ted Naiman; for training, Menno Henselmanns and Drew Baye.

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