You lose about 1/2 inch of body height throughout the day through vertebrae compression. Their height difference could simply be down to him being in the US for

You lose about 1/2 inch of body height throughout the day through vertebrae compression. Their height difference could simply be down to him being in the US for a long period of time, I know having been to the US and currently living in Canada that any trip back to the UK means major sleep problems, I'm up either majorly late or direly early. Could it simply be that he gets up far earlier than his brother (British culture is notably more 9-5 than NA culture, where 7-3 is highly noticeable, at least here in Ontario)? Would the increase weight mean faster compression of his vertebrae or even excess compression compared to his twin? Not to mention posture and everything else, including flat-footedness (which IIRC can attribute a decrease of about 1/2 inch in height due to a posture shift), which again could have been induced by excess weight. Both twins could be genetically prone to flat feet, but the shorter one simply gained weight and increase the strain leading to a collapse earlier in life. Perhaps this is DNA methylation, but I'd bet anything that a mixture of diet, exercise and physical health are greater contributing factors to divergent physical characteristics in identical twins. I mean one simply taking a disliking to milk through childhood, or getting repeatedly put in detention could have a large enough effect over time to decrease physical height by less than an inch.