The first is easy to rule out. Just eat lightly, and see how you feel. The second is much more common, so chances are you' re overdosing on refined carbohydrates. If you' re lunching on pasta, baked potatoes, sandwiches or wraps made with refined bread, sugary drinks, tea or coffee or snacks like chocolate, beware: all these can send your blood sugar through the roof. In too short a time it then comes crashing down and you end up feeling sleepy or exhausted. If this sounds like you, try eating something like a piece of fish or chicken with vegetables or salad only. If this makes a difference, make sure from now on that when you lunch, any serving of starchy carbohydrate such as rice, potatoes, bread or pasta is balanced out by a serving of protein (fish, meat, tofu, cottage cheese or hummus) of equal size. Drink water, herbal teas, coffee substitutes and diluted juices instead of tea or coffee, and snack on fresh fruit paired with nuts and seeds if you' re hungry after lunch. The mineral chromium can also help stabilise your blood sugar; take 200mcg with lunch.

The most common reason for wanting to snooze after lunch, however, is a food allergy. Perhaps 1 in 10 people have minor reactions to certain foods, the most common being drowsiness. For some people it' s yeast, for others wheat, milk, beef or soya. I thought I was allergic to wheat because I was drowsy after eating bread. I wasn' t. After testing, I realised I was reacting to yeast, which is present in bread and beer, but not in pasta and champagne. It' s worth investing in such a test to discover any food intolerance you may have.