The 'Heathrow Injection' is a colloquial term for the massive weight gains that people moving to the UK inevitably experience. Most probably due to a less healthy diet, lower level of exercise and cramped living conditions, the condition is usually met by confusion and disbelief. Rather than face the fact that plainly more time is needed in the Gym, the condition is diagnosed by most of it's sufferers as simply 'the Heathrow Injection'.
Females suffer this condition more than males generally. The rate of affliction is probably equal, however the males often have the advantage of patting the stomach and remarking 'It's all paid for'.