The science behind nutrition is a treasure trove of myths and speculation. One such tale is the existence of negative calorie foods, which use up more calories to be digested than they provide to the body, therefore causing you to lose weight. If it sounds too good to be true, that’s because it is!

To understand the science behind this topic, we need to know how our bodies burn calories. We all have a different basal metabolic rate (BMR), which refers to the amount of energy we need at complete rest to power blood circulation and other essential tasks. This makes up the bulk of calorie loss, complemented by physical activity and digestion.

Digestion causes a rise in metabolism when it produces heat energy. But it only contributes 10 per cent of our daily energy expenditure. So if we eat 2,000 calories a day, 200 are burned when digesting.

Celery is a prime candidate for negative calorie food. It is mainly made up of water and fibre, and is low in calories, with a large stalk containing around 10 calories. While eating celery requires energy to break down the fibre, it does not burn more than the 10 per cent average (just one calorie), so is not calorie negative.

Protein-rich foods such as meat give up more of their calorie content as heat, as the process of breaking down protein into its constituent parts takes up a lot of energy. This gives rise to the ‘meat sweats’ phenomenon. You might want to avoid these in summer!

There is one form of sustenance that is calorie negative: cold water. It has zero calories and takes energy to be heated up to body temperature, even if it’s only a small glass full.