You eat healthily. You exercise regularly. You avoid too much booze and wave away the dessert trolley.

Why then, is your waistline refusing to be whittled by your efforts? If belly fat is your arch enemy, you'll know that it can be a tricky customer to eradicate. In fact, fat in this area can stick around for a number of unusual reasons. Here are three things that might be affecting your middle: You're not getting enough sleep: Studies show that women who get less than five hours sleep per night are 30 per cent more likely to gain more than 30lbs over 16 years than those who slept for seven hours or more per night. The Remedy: Hit the sheets two hours earlier than usual twice a week. Leave your phone downstairs and read a book to unwind. Chances are you'll be asleep in 30 minutes. You live in the city: People who live near a busy street have been shown to have higher BMIs and more belly fat. Scientists found that people who are regularly exposed to the noise of traffic are 25 percent more likely to have larger waistlines - and women are more vulnerable than men. The Remedy: It's not cheap but look into triple glazed windows to reduce traffic noise. If you rent, earplugs can be useful when you're trying to drop off, while New Yorkers swear by soothing music, pink noise and meditation tracks. You're not getting enough calcium: Most women don't get the recommended amount, but calcium suppresses the fat storage hormone so we're really missing a trick. A University of Tennessee study showed that women who ate six ounces of fat-free yogurt with every meal lost a whopping 81 per cent more abdominal fat than women who only cut calories. The Remedy: Swap your little treats (that sugary coffee, that mini Snickers bar) for a low fat yogurt. Not only will you save on calories, you'll also boost your calcium intake.