A typical 18–20 year old man requires a daily input of about 12 MJ; a woman of
the same age needs about 9 MJ. If the entire consumption were in the form of glucose
(3; which has a specific enthalpy of 16 kJ g−1), that would require the consumption of
750 g of glucose for a man and 560 g for a woman. In fact, digestible carbohydrates
have a slightly higher specific enthalpy (17 kJ g−1) than glucose itself, so a carbohydrate
diet is slightly less daunting than a pure glucose diet, as well as being more
appropriate in the form of fibre, the indigestible cellulose that helps move digestion
products through the intestine.