The study of the amount of the different forms of diet which is needed
by people at rest, and by those who are active, is valuable only to
enable us to construct dietaries with care for masses of men and where
economy is an object. In dealing with cases such as I shall describe, it
is needful usually to give and to have digested a surplus of food, so
that we are more concerned now to know the forms of food which thin or
fatten, and the means which aid us to digest temporarily an excess.

As to quantity, it suffices to say that while by lessening food we may
easily and surely make people lose weight, we cannot be sure to fatten
by merely increasing the amount of food given; something more is wanted
in the way of digestives or tonics to enable the patient to prepare and
appropriate what is given, and but too often we fail miserably in all
our means of giving capacity to assimilate food. As I have said before,
and wish to repeat, to gain in fat is, in the feeble, nearly always to
gain in blood; and I hope to point out in these pages some of the means
by which these ends can be attained.

_Note_.--The statements made on page 21 and the following
paragraphs about obesity in England and with us are no longer
exact, but have been allowed to stand in the text as recording
facts true at the time of writing them, in 1877. At the present a
medical observer familiar with both countries must note several
decided changes: more fat people, more people even enormously
stout, are seen with us than formerly, and fewer of the
"inordinately fat middle-aged people" in England than used to be
encountered. With us the over-fat are chiefly to be found among the
women of the well-to-do classes of the cities, and from thirty
years old onward. They persecute the medical men to reduce their