The late winter surgeries which characterise these grey days generate a more-than-usual need for chocolate, and you know what they say about Lycra swimsuits (squeeze it in if you like, it will only pop out somewhere else).

Something must clearly be done, but endless repeat HAD scores would be unbearable without the occasional chocolate Buttons.

I was cheered, therefore, to discover a solution in a national newspaper which published a two-page spread of 'offsetting', telling me exactly how to offset the many indulgences that drive my day.

Did you know that eight pieces of sushi are offset by 50 minutes of ballet? Does this help you in any way? No, it is of no use to me either, other than to confirm I had best continue to stay away from sushi lest the urge to don pink tights and a tutu becomes overwhelming.

On the other hand, two fingers of Kit Kat are offset by 71 minutes of ironing - a good reason never to eat Kit Kat again. A glass of red wine disappears with 20 minutes of sex, which explains why we don't drink in the surgery, and a slice of cake requires 54 minutes playing Twister, which will liven up our next practice meeting no end. A glass of low calorie lemonade is erased by six minutes of laughing, an oddly depressing thought, as laughter should not be quantified.

A kebab can be despatched by one night of clubbing, which means late evening surgery (at which the take away man calls) could end with me in a micro-mini gyrating on a dance floor while playing the violin (37 minutes of Vivaldi for one bottle of Coke).

I am already plotting a week of kebabs and cake, and a press campaign for a recreational boating lake, when I come across the best fact of all - an entire Snickers bar is wiped out by six hours and 40 minutes of sleep. This is good news indeed, and I drop all other plans and buy several packets at once. The future looks rosy.

• Dr Selby is a GP from Suffolk.
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