( Calories ( ( are ( ( nothing more ) ( than ( ( ( a unit ) ( of heat ) ) ( used ( to ( express ( ( the ( energy value ) ) ( of food ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Calories)) (VP (VBP are) (ADJP (ADJP (NN nothing) (JJR more)) (SBAR (IN than) (S (NP (NP (DT a) (NN unit)) (PP (IN of) (NP (NN heat)))) (VP (VBD used) (S (VP (TO to) (VP (VB express) (NP (NP (DT the) (NN energy) (NN value)) (PP (IN of) (NP (NN food)))))))))))) (. .)))
Calories are nothing more than a unit of heat used to express the energy value of food.
(ROOT (S (NP (NP (DT The) (NN energy) (NN content)) (PP (IN of) (NP (NNS foods)))) (VP (VBZ is) (ADVP (RB often)) (VP (VBN expressed) (PP (IN in) (NP (NNS calories))))) (. .)))
The energy content of foods is often expressed in calories.