Dining out is becoming more common in many countries, and some studies suggest that people who eat out more frequently are at increased risk of weight gain and obesity.

Two research papers published this Christmas by The BMJ have taken a look at how calorific restaurant food is - both in the UK (https://www.bmj.com/content/363/bmj.k...) and in countries around the world (https://www.bmj.com/content/363/bmj.k....

How do scientists actually measure the calorie content of food? Thanks to the team at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, we bring you the science of a calorimeter.