If you're the life and soul of the breakfast table, even on dark mornings, chances are you're a "lark". But while "larks" wake an hour earlier than average, "owls" dread the darker months, lying in well past sunrise.
"Owls only start to feel better later in the day and tend to turn in an hour or two later than average," says Professor Jim Horne, director of the Loughborough Sleep Research Centre.
According to Horne, 15 per cent of us are larks, 15 per cent are owls and the remaining 70 per cent are neither one or the other (although there may still be leanings towards morningness or eveningness within this 70 per cent).
There are advantages to being an evening person, with studies suggesting they tend to be more extrovert and have a better sense of humour, but there are considerable downsides. Starting most days unwillingly is not fun, especially in winter. Nor is being assumed to be lazy. When it comes to business success, morning people have the upper hand, not least because they're in sync with the corporate schedule and have been found to be more conscientious.
But owls can retrain themselves.
Each of us has a circadian rhythm - our internal body clock - which peaks and troughs at certain times of the day.
"There are around a dozen genes and their corresponding proteins involved in the ticking of this clock," says Simon Archer, reader in chronobiology at the Surrey Sleep Research Centre.
"A morning or evening preference is 50 per cent inherited - quite a lot for a behavioural characteristic. One gene, Period3, is significant as we've found that people with a long version of it are much more likely to be morning types and those with the short version are likely to be evening types."
Age is another contributory factor, with children more likely to be larkish, then turning to owls in adolescence and reaching a peak of owlishness in their early 20s, he says.
"Then we become more morning types as age. We think it's because sleep becomes more fragmented as we get older. When old people wake early, they find it difficult to get back to sleep."
Habit and cultural influences play a part, too. Traditional work schedules or children force you to rise early until you get used to it.
GET UP AND GO
Set your wake-up time and stick to it like glue. If you sleep more than 90 minutes later on a Saturday or Sunday, you'll inadvertently readjust your body clock to the later wake-up time just in time for Monday morning.
Lose the snooze button too, says Jason Ellis, director of the Northumbria Centre for Sleep Research.
"You are better off setting the alarm for the time you really have to get up. The extra sleep will be of better quality. Jump straight into the shower to regulate the bodily system."
If you can, fit in a workout, he adds - so long as you're not sacrificing sleep to do it. It starts to speed your metabolism up, leaving you feeling fresher by pumping oxygen to the brain. He advocates swimming or yoga. Gyms usually offer personal training and group fitness for early birds, too.
SEEK OUT SUNLIGHT
Circadian rhythms are influenced by light exposure, which adjusts your body clock and suppresses the release of melatonin, a natural hormone that signals your body that it's time to sleep. It's one of the reasons many of us find it easier to get up in the summer.
"Immediately after awakening, expose yourself to bright light for at least 20 minutes - walking or exercising outside or having bright lights on while you eat breakfast," says Professor Adrian Williams, director of the Sleep Centre at Guy's and St Thomas' Hospital and partner at the London Sleep Centre. You may even consider a special light box or portable light visor around the house.
"A lot of people who say they aren't morning people are simply people who skip breakfast and therefore feel more and more tired until lunchtime," says Sara Stanner, a nutritionist and spokesperson for the Breakfast Panel.
Our bodies use up glucose in the night so our organs and cells can maintain their normal function, she explains. Within two hours of getting up, that glucose needs restoring. No wonder research shows people who miss breakfast are less productive and less alert. Opt for slow-releasing carbs - ideally mixed with protein and fibre. Egg or beans on toast is good, as is oatmeal porridge with nuts and seeds.
"I'd recommend cereal, too," adds Stanner, "especially with added vitamins and minerals, notably folic acid and iron for women, because low levels of these can make them especially tired.
"The main thing is not to go for anything too sugary like a muffin or croissant, which will give you an instant but short-lived energy boost. Your blood sugar will drop as quickly as it rose, leaving you more desperate than ever to be back in bed."
Don't forget a drink, she adds. "If you're dehydrated, you'll feel lethargic."
And once you start eating breakfast, chances are you'll wake up earlier because you're hungry.
GO TO BED AN HOUR EARLIER
Duration of sleep is less related to morning alertness than you might expect. But just because the number of hours of sleep doesn't matter, the timing of the sleep does. So by going to bed an hour earlier, you could help shift your daily cycle. Also, going to bed and getting up at roughly the same time programmes your body to sleep better - and the higher the quality of sleep, the less groggy you're likely to feel in the morning.
To help you sleep, adapt your environment, advises Maria Gardani, research fellow at Glasgow Sleep Centre - no TVs or computers in the bedroom. Avoid alcohol, caffeine, bright lights and exercise, which can rev up the body, for at least a few hours before bedtime.
"Don't even read in bed. It's all about winding down," she says.
In the US, an over-the-counter synthetic version of the sleep hormone melatonin is available and it's often one of the first things wannabe larks buy. In New Zealand it is a prescription-only product, although you can buy it on the internet. Don't, says Ellis - you can never be sure what you're getting. If you really think you need it, see a sleep clinic.
A safer alternative, he says, is foods that are naturally high in melatonin such as walnuts and tart cherries.
"Try a cherry juice and a handful of nuts. Also consider foods containing tryptophan, which help stimulate the production of melatonin. These include eggs, cereal, bananas and turkey."
Until a couple of years ago, it was believed that the whole circadian cycle was maintained by the brain. Not so, Ellis says.
"We now know we also have little clocks in our lungs, liver and pancreas - all areas relating to food. So you can change some of your clock's timings by changing what you eat and when you eat it."