>> Most of the pairs had maintained remarkably similar exercise routines, despite living apart.
> Besides the testament to how 'everything is heritable' inherent in that observation [...]
>> Interestingly, the twins tended to have very similar diets, whatever their workout routines, so food choices were unlikely to have contributed to health differences.
> Also very interesting, and counter to the usual narratives about health. (Everything is heritable...)
Why do you think this proves genetic causes? They were twins, after all, they were both socialised under the exact same circumstances for two decades. Given they had identical upbringing, I'm not surprised that e.g. their preferences to food are quite similar.
Because shared environment effects are typically small or trivial. You don't need a formal analysis to have a high confidence that the food preferences will be partially or mostly heritable, just like everything else. In particular, we already know that anything to do with obesity is extremely heritable and shared environment matters far less than everyone believes: see the studies in https://jaymans.wordpress.com/obesity-facts/
Thanks for the response, I'm just reading through the linked meta analysis.
It's important to remember, though, that correlations measured in twin studies, by design, only say something about the difference of both measured variable expressions, not about the variable itself. So if twin A has a BMI of 30 and twin B has a BMI of 35, that linked meta analysis says that heredity explains 75% of the difference between 30 and 35, or only 3.75 BMI points/ 10% of twin B's BMI in the given example. Even more interesting: The older the twins are, the smaller the difference gets (grep for 'decreased mean age' in the study).
This is certainly the stronger assumption. Eating habits in particular are very social and habitual. It doesn't stretch the imagination to imagine the twins, having lived in a single household for >=18 years, have a deeply set familiarity with certain foods, recipes, etc.
> Besides the testament to how 'everything is heritable' inherent in that observation [...]
>> Interestingly, the twins tended to have very similar diets, whatever their workout routines, so food choices were unlikely to have contributed to health differences.
> Also very interesting, and counter to the usual narratives about health. (Everything is heritable...)
Why do you think this proves genetic causes? They were twins, after all, they were both socialised under the exact same circumstances for two decades. Given they had identical upbringing, I'm not surprised that e.g. their preferences to food are quite similar.