<P> Using the International System of Units , researchers measure energy in joules ( J ) or in its multiples ; the kilojoule ( kJ ) is most often used for food - related quantities . An older metric system unit of energy , still widely used in food - related contexts , is the calorie ; more precisely , the `` food calorie '' , `` large calorie '' or kilocalorie ( kcal or Cal ) , equal to 4.184 kilojoules . ( Contrast the `` small calorie '' ( cal ) , equal to 1 / 1000 of a food calorie , that is often used in chemistry and in physics . ) Within the European Union , both the kilocalorie ( `` kcal '' ) and kilojoule ( `` kJ '' ) appear on nutrition labels . In many countries , only one of the units is displayed ; in Canada and the United States labels spell out the unit as `` calorie '' or as `` Calorie '' . </P>
<P> Using the International System of Units , researchers measure energy in joules ( J ) or in its multiples ; the kilojoule ( kJ ) is most often used for food - related quantities . An older metric system unit of energy , still widely used in food - related contexts , is the calorie ; more precisely , the `` food calorie '' , `` large calorie '' or kilocalorie ( kcal or Cal ) , equal to 4.184 kilojoules . ( Contrast the `` small calorie '' ( cal ) , equal to 1 / 1000 of a food calorie , that is often used in chemistry and in physics . ) Within the European Union , both the kilocalorie ( `` kcal '' ) and kilojoule ( `` kJ '' ) appear on nutrition labels . In many countries , only one of the units is displayed ; in Canada and the United States labels spell out the unit as `` calorie '' or as `` Calorie '' . </P>
how do we measure the energy content of food
how do we measure the energy content of food
the calorie ; more precisely , the `` food calorie '' , `` large calorie '' or kilocalorie ( kcal or Cal ) , equal to 4.184 kilojoules
the calorie ; more precisely , the `` food calorie '' , `` large calorie '' or kilocalorie ( kcal or Cal ) , equal to 4.184 kilojoules