Birthdays, hypos and other hard cases

If you have diabetes. I said it in the preface and I'll repeat it. If you treat low blood sugar with sugar, that's medicine, and it comes before any rule in this book. Beyond that, how much sugar suits you, and when, is a matter for you and your diabetes team.

If the office produces cake most days. Workplace cake presents itself as an occasion but happens too often to be one. A colleague's birthday once a month is an occasion. A permanent supply on the filing cabinet is a tin that someone else keeps full. A workable line is to join in for a named celebration and leave the everyday supply alone. "Not for me, thanks" is a complete answer and needs no explanation. If you'd like a slice of someone's homemade cake, ask to take it away and have it with your lunch.

If someone at home keeps the tin full. Tell them what you're doing and why. You're not asking them to change, only to let you keep your own supplies out of your way. Most partners are happy to have the biscuits in a different cupboard. If there are children, their snacks can live in a box that's theirs.

If someone shows love with sweet things. Your mother-in-law's trifle is about her, not about sugar. Have some with the meal and enjoy it, which is what the rule says anyway. If she presses a bag of fudge on you for the journey home, accept it, because what she's offering is affection. What happens to the fudge later is your business.

If cravings come with your cycle. Many women find that the pull towards sweet things is stronger in the days before a period. I haven't looked into the research on this and won't pretend to explain it. The practical point is that a stronger urge is still an urge, which means it rises and passes. Pudding with meals is still available on those days, and you might make it a good one.

If you do long or hard physical exercise. Sugar during or straight after a long run or ride is fuel for working muscle and is outside the scope of this book. The three jobs are about desks and sofas.

If you're pregnant. Follow your midwife's advice on eating. Nothing in the rule involves going hungry or cutting out any food, but this isn't the time to take dietary instruction from a general book.

If you switch to sugar-free versions. Diet drinks and sweetened snacks keep the habit going with a different ingredient. Your teeth may be better off, but the three jobs are still being given to a sweet taste, and the reward, the pick-me-up and the comfort are still being done badly. I take no position on sweeteners themselves, which is a separate argument, and the NHS does suggest sugar-free drinks as a swap for sugary ones. If the swap helps you, use it. My own suggestion is to treat sweet-tasting things as sweet things for the purposes of the rule, because the jobs are what this book is about.

If you work nights or shifts. Meals are whenever you have them, and the wall arrives at four in the morning when the vending machine is the only thing open. Bring real food for that hour, and use the walk.

If you're in a really bad stretch. In the first weeks after a bereavement, or while someone's in hospital, leave the rule alone until life steadies. Eat what gets you through. Those weeks don't count against you, and you can pick the rule up again afterwards.

If eating starts to feel out of control, or rules about food start to take over. Go back to the preface. Eating large amounts in secret, feeling unable to stop, or finding that you're anxious and rigid about what you eat, are all reasons to see a GP and not to try harder with this book. Beat's helplines are there for exactly this.