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.
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?
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.
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 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.