( ( Calories ( measure ( ( the ( energy content ) ) ( of ( the food ) ) ) ) ) ( we ( eat . ) ) )
(ROOT (S (S (NP (NNS Calories)) (VP (VB measure) (NP (NP (DT the) (NN energy) (NN content)) (PP (IN of) (NP (DT the) (NN food)))))) (NP (PRP we)) (VP (VBP eat)) (. .)))
Calories measure the energy content of the food we eat.
(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.