The festive season is over. The time for guilt is nigh. But is foreswearing alcohol, junk food or caffeine for just one month really any good for your health?
Newspaper articles saying that we typically eat 7,000 calories on Christmas Day are fresh in the mind. Evidence of sustained merry-making is perhaps hanging off our waists.
As a result, many decide January is the time to try and get healthier by giving something up. But does it work?
"It's always a mistake to think you can undo the sins of 11 months in one month's good behaviour," says Sir Ian Gilmore, special adviser to the Royal College of Physicians on alcohol.
The idea that you can create a new habit in three weeks is a myth, according to psychologists at University College London. Their research suggested that it was more like 66 days. That would mean giving something up until 8 March.
Others say it depends. Not just what you give up, but how you respond once the month is up.
It's arguable that alcohol is the best thing to give up. The liver, responsible for detoxifying alcohol, is about the only organ capable of regenerating itself in weeks. A regular social drinker who goes on the wagon will lose a significant proportion of the fat that has built up on their liver within a month, says Dr Gary Murray, an expert at the US's National Institute on Alcohol Abuse and Alcoholism.
"The liver is an amazing organ because it has a tremendous regenerative capacity," he says. But for a heavy drinker with more serious liver damage, such as fibrosis - where the liver is scarred - a month will not see the liver go back to normal.
A controlled experiment at the New Scientist revealed that liver fat, blood glucose and cholesterol levels all decreased noticeably among magazine staff who abstained from alcohol for five weeks.
Gilmore agrees that the liver can regenerate after a few weeks. But what happens next? If the drinker goes back to their previous ways, does that month off help? No-one really knows, he says.
It's not just the liver. The pancreas, brain and heart are all negatively affected by heavy drinking. But none has the regenerative powers of the liver. To complicate things, there is evidence suggesting that low alcohol consumption is better than no alcohol to avoid heart disease. However the amounts recommended are very low. The maximum benefit derives from one glass of wine twice a week, Gilmore says. And the benefit doesn't kick in till women reach 60 and men 45.
Gilmore says a month off is useful but more for the mental rather than physical benefits: "I think the main benefits are intangible." First it shows you that you can do it. Those who find it impossible will discover they are alcohol dependent - 1.5 million people in England are thought to be in this position.
If you go back to your old ways, then the month is more or less wasted, he thinks. But the intelligent abstainer will learn from the experience. You will feel generally better, sleep better, be less stressed and find you have more time for other things. And as a result, will see the benefits of changing your behaviour.
There's no need to become teetotal but just to adopt a more moderate approach. For life - as opposed to January - it's important to have two to three alcohol-free days a week to let your liver recover, as well as drinking within the recommended limits, he says.
What about smoking? As soon as you stop you cut the risk of a heart attack by about a quarter, says Robert West, professor of health psychology at University College London, and author of the SmokeFree Formula. The half-life of nicotine is two hours - within 24 hours you can no longer detect it in the body. Within a few days, hands and feet warm up because nicotine constricts capillaries in the extremities.
In the same time frame, the smoker's tremor goes and sense of smell returns. In the first couple of weeks breathing improves but you will develop a cough and may start to feel "rubbish". The cough and sense of feeling rough will last days rather than weeks. By the end of the month you will be less stressed and more stable - there are no more highs and lows based on nicotine withdrawal symptoms. And your skin will look five to 10 years younger.
But is there much point giving up for just a month? In itself, no. Unlike the liver, the lungs will not clean themselves out. But the target of a smoke-free month is a good one, Prof West says. "With smoking most of the struggle is right at the beginning. You can say I'll give up for a month and see how I go." By the end of the month, you may be ready to make the break permanent. And even if you go back to smoking, there's evidence to suggest that staying off cigarettes for a month helps smokers to give up in the long run.
Many will have overeaten at Christmas. Not everyone is convinced by banning food vices for a month, however. " You've either got to do it long-term or not at all," says Lucy Jones, spokesperson for the British Dietetic Association. A more balanced diet is better than "all or nothing", she argues. Between 7% and 9% of all mortality is to do with not eating enough fruit and vegetables, she says.
But what if you were to focus on a modern bogeyman - the carbohydrate? Most doctors and nutritionists agree you will lose weight if you give up carbs for a month. But there are different views about which carbs should be shed and whether such an approach is actually healthy.
Everyone agrees sweets, biscuits and puddings should go. But what about white carbs, such as white bread or white rice? Or should you try and cut out all carbs, even wholemeal varieties?
Amanda Ursell, nutritionist for the Times calls the first group "empty calories."
"They're fine if you're going to the South Pole. And most of us don't need any more calories. So yes absolutely cut out cake, biscuits and sweets for January."
Starch is a more vexed issue. The NHS recommends starchy foods should form about a third of someone's diet.
But some doctors believe that pasta, rice and bread are too prominent in our diets causing sugar highs that trigger insulin to be released into the blood stream. "High levels of insulin drive fat storage and can make maintaining a healthy weight more difficult," says Dr John Briffa, author of A Great Day at the Office .
However, it's important not to go overboard, says Dr Sarah Jarvis, GP and regular on the BBC's The One Show. "We need to differentiate between refined and unrefined carbs." Giving up white bread, white rice and non-wholemeal pasta - as well as the biscuits and cakes - would make sense, she believes.
Ursell agrees that wholegrain is best but says the odd white slice won't hurt. True, white bread it is higher in GI than table sugar. But people usually eat it with things like meat or cheese so shouldn't be viewed in isolation. "Cutting out all carbs you are very likely to lose weight." But it's better to leave in the porridge, cereals and wholemeal bread - otherwise you'll miss out on B vitamins, zinc and iron. "Give up cakes, biscuits and puddings for January. Don't have rice and nan with your curry, choose just one." People used to eating a lot of these foods, will lose weight. Their gut will diminish. And they will be more stable from an energy point of view, she says.
Many people rely on caffeine to get them through the day. Is it a good experiment to give up tea and coffee for a month? It probably is, says Peter Rogers, professor of biological psychology at Bristol University, who thinks a month off will show people how dependent they are. Regular tea and coffee-drinkers are dependent with no net benefits, he argues. Most caffeine in the body is eliminated overnight. So the feeling that you need a shot of coffee to get started in the morning is just removing the withdrawal symptoms.
And after a month off, he says, you can use caffeine strategically - only when you really need it, such as for a long drive. Most experts agree that a month is long enough to overcome caffeine withdrawal symptoms. But in the first few days, you may have a headaches, warns Jarvis. You might feel drowsy at times. It's not a good idea to give up just before you have a long drive or important piece of work, says Rogers. By the end of the month you will probably feel more balanced, sleep better and feel less jittery, Rogers says. But this is a lifestyle choice not a health decision. There's no evidence to show that caffeine is bad for you. There's even research suggesting it may guard against Alzheimers disease.
"Giving up caffeine wouldn't be top of my list to improve my health," Rogers says. Jarvis says with the exception of one group, there's no benefit to giving up caffeine for a month, or permanently. People who get migraines might find it worth trying - avoiding caffeine might help stop the headaches. Drinking 400-450mg of caffeine a day is safe for everyone except pregnant women who should drink less, she says. (There's about 50mg in a cup of tea or shot of espresso). So while Prof Rogers advocates weaning yourself off, others might think the pain of sitting out another tea round to be a cruel and unusual January punishment.
It's common to give up chocolate for Lent. But what happens when you avoid chocolate for a month?
It depends what type you're giving up. Milk chocolate is high in sugar and low in cocoa. For example, Cadbury's Dairy Milk and Mars Galaxy have a minimum of 26% and 25% cocoa respectively. Even some dark chocolate is low in cocoa - Cadbury's Bournville has a minimum of 36% cocoa. But chocolate of 70% cocoa or more, should be viewed differently, Ursell says. "Personally, if I had to give up chocolate, it would be milk chocolate because there is emerging evidence that the relatively high antioxidant content in 70% cocoa dark chocolate may be of some benefit to heart health and that it may even help to curb our appetite," says Ursell.
But when it's cold and wet outside, the lure of dunking a milk chocolate biscuit into a warm cup of tea might prove just too tempting.
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