Dieters are forgetting to count the calories in alcoholic drinks, with one pint of lager containing the same amount as three chocolate biscuits.
Each year millions of people make a resolution to lose weight after over-indulging during the festive period.
But health charity the World Cancer Research Fund (WCRF) is warning people against regular drinking.
It says if you often enjoy a glass of wine or a pint of beer with dinner, alcohol could be making up nearly 10% of your total daily calorie intake.
According to WCRF, alcohol contains 7 calories per gramme. This is only slightly less than fat, which has 9 calories per gramme, and is filled with "empty calories".
Kate Mendoza, head of health information at WCRF, said: "The calories in alcoholic drinks account for a significant proportion of a drinker's calorie consumption while providing little, if any, nutritional benefit."
Alcohol Calorie Counter
To help drinkers monitor their intake, the WCRF has produced an online alcohol calorie calculator which shows how much moderate exercise is needed to burn off a range of alcoholic drinks.
A large glass of wine contains 178 calories, the equivalent of two chocolate digestive biscuits, and would take half an hour of brisk walking to burn off.
One pint of lager contains 250 calories, the same as three chocolate digestive biscuits, which would take 53 minutes of brisk walking to burn off.
A spirit and a mixer, although a slightly lighter option, still contain 117 calories.
In addition to calories, it's also important to make sure you're keeping tabs on how many units you're having. To estimate how much you're having each week, have a look at our alcohol unit calculator.
Alcohol a 'risk factor'
Cutting down on alcohol intake will not only help you lose weight, but it will also reduce your chance of cancer, says the WCRF.
Being overweight is the biggest cancer risk factor after smoking.
Mendoza said: "There is also strong scientific evidence that alcohol itself is a cancer risk factor - possibly through damaging our DNA."
In fact, drinking as little as one pint of beer every day increases your risk of liver cancer and bowel cancer by about a fifth. More than 20,000 cases of cancer a year are linked to alcohol in the UK, says Mendoza.
A number of charities have started campaigns to encourage people to cut back on their drinking or stop completely, including Alcohol Concern’s Dry January.
The WCRF recommends that, if consumed at all, alcoholic drinks should be limited to two for men and one for women a day.
Cutting down on alcohol, maintaining a healthy weight and getting regular exercise are just a few of the ways you could reduce your health insurance premiums.