Holiday weight gain = 1/2 a kilo. That's 4000 calories (give or take) which is pretty much eating twice as much as I should for a day and a half, which is as you would expect, considering that on Christmas day I did not get in my customary run. I did on Boxing day, but it was a sad little jog dragging my slow and sorry arse around Birkenhead. Yesterday was a marked improvement, and today at the gym I felt quite a bit better. However, it will be a long slog.
You see, your body is a set of scales, energy in minus energy out. But it is considerably harder to force energy out (refer, for example to this calculator which shows the calories expended in exercise) than it is to force in another mince pie. Then there is calorie restriction: I can rarely manage a deficit of more than about 250 calories a day, so you can see that it would take a good 12 days at that rate to get back to where I was. However, it is unlikely that I will manage a deficit until after New Years Eve, so I will probably be lugging the fatty residue from my indulgence around for the better part of a month before I am back to pre-Christmas levels.
Such is the grim mathematics of eating. As my nutritionist said once: you can always out-eat your exercise programme.