11. Annexe 2: Energy density and obesity
11.1 The energy density of a food is defined as the number of calories contained per gram and is dependent upon the composition of the foodstuff. The water content of a product will reduce energy density (because it contains no calories per gram), whereas the presence of fat (with nine calories per gram) and/or sugar (with four calories per gram) will increase energy density.
11.2 Energy dense foods have been defined by the World Cancer Research Fund (WCRF) as those with an energy content of more than about 225–275kcal per 100g. Sweet biscuits (average 477kcal per 100g), confectionery (average 435kcal per 100g), crisps and savoury snacks (average 501kcal per 100g) and cakes, pastries and puddings (average 362kcal per 100g), are all very energy dense. The 2007 WCRF food, nutrition, physical activity and the prevention of cancer report recommends that the average energy density of diets should to be lowered towards 125kcal per 100g.
11.3 There is also an inverse relation between energy density and energy cost (£/kilocalorie), such that energy-dense foods and diets may often represent the lowest-cost option to the consumer. This is evidenced within research from Drewnowski and Specter (2004), Waterland et al. (2010) and the 2011 Food Standards Agency report on the Scottish diet: estimations of energy density and expenditure.