Some myths just refuse to die. They say that chewing gum stays undigested for seven years, food dropped on the floor is safe if picked up within 10 seconds and cracking your knuckles will eventually cause arthritis.

They are all fallacies, and the list could go on. One particularly stubborn fable is the enduring belief that celery has negative calories – and eating it burns more calories than it contains.

It’s an idea that sounds logical at first: celery has hardly any calories in it and because it is a bulky, fibrous plant, the body must surely burn more energy chewing and digesting it than it contains. The more celery we eat, the more calories we burn, therefore making it the perfect calorie-burning, guilt-free food.

It’s not just celery, though, as there are dozens of websites and health ‘experts’ who insist that kale, cucumber and kelp noodles are also negative calorie foods and will cause weight loss.

None of these armchair nutritionists back up their claims with evidence; even though their cookbooks sell better than cupcakes. So, having spent some time chewing over the facts, I can reveal that negative calorie ideas are wishful thinking.

Every time we eat some of the energy (calories) contained in the food is ‘wasted’ – given off as heat as part of the digestive process. This is called the ‘thermogenic’ effect of a food and explains why we feel warm after eating a big meal or suffer ‘meat sweats’ after gorging a 15oz rib-eye steak.

Each food has a different thermogenic effect; and on a typical day we will burn at least 200 calories (the same as a small chocolate bar) from the process of digesting food.

Crucially though, celery has a tiny thermogenic effect – less than even the meagre six calories each stalk contains. The green, stringy plant stuff (fibre) that we swallow passes straight through the gut, but with your body doing very little to it on the way.

Chewing burns little energy and the body doesn’t bother wasting energy trying to digest something it can’t. In fact, the only way you could burn six calories from eating a stalk of celery is to chew it for at least 25 minutes.

Of course, this doesn’t make celery a worthless food. There are many reasons for adding vegetables and fibre-containing foods to your diet. Plant-based foods are often abundant in nutrients and confer very many health benefits. So while the negative calorie foods don’t exist, eating plenty of vegetables will help weight control and weight loss. Fibre-containing foods add bulk to your diet and help to keep you full while keeping blood sugar levels steady. Eating celery can be good for you –just don’t think that negative calories will undo the hummus it is smothered in.