The truth about calories.

In episode 2 of a series about nutrition, presenter Christoffer (Chris) van Tulleken investigates calories. Van Tulleken explains how calories in food are derived from plants’ absorption of sunlight. He lists the three providers of calories: carbohydrates, protein and fat. Van Tulleken visits a food laboratory in Kent, and tests randomly purchased supermarket food to check the calorie count accuracy; all revealed to be within the 10% government guidelines. Dr Jason Gill helps to devise the ‘Big Calorie Challenge’ with 3 volunteer families from Glasgow. All eat a 600 calorie breakfast and then spend their morning either at the gym, doing housework, or doing nothing. Gill advises slow and steady activity is more effective at burning calories than shorter intense exercise. Van Tulleken meets with explosives expert Charlie Adcock and burns various foods to demonstrate their energy content. Anatomist Claire Smith explains the human digestive system. She and van Tulleken discuss different absorptions dependent on type of food. The results of the ‘Big Calorie Challenge’ are revealed, with housework being the most effective calorie burner. Van Tulleken runs an experiment by setting up a stall selling smoothies. He makes a batch of 500-calorie smoothie, markets one half as a 200-calorie healthy drink, and the other as a 900-calorie luxury. Pairs of twins test, with the ‘low’ calorie twins becoming hungry sooner, whilst their ‘high calorie’ twin remain full for longer. Van Tulleken discusses the high calorie content of alcohol describing such substances as ‘calorie dense.’ He visits a major supermarket test kitchen and taste low-calorie versions of ready-meals. Nutritionist Amanda Ursell assists in a final experiment in a Glasgow restaurant. One table of volunteers receive a full 1800 calorie lunch, whilst a second get a ‘low-calorie’ version to ‘strip’ the calories away without removing ingredients. Techniques such as cooking rarer steaks and reducing portion size cause van Tulleken to declare it a success. He aims to apply what he has learnt by balancing his daily calorie intake with his used energy, but still runs over by 100 calories.