our “sweet tooth” and continued to eat fruit. Until the discovery of fire, all food
was eaten raw, which kept the delivery of nutrients to our systems very slow.
This prolonged digestive time provided satiety and did not strain our metabolic
or hormonal systems.
Exercise and movement were an intrinsic part of everyday life. Our ancestors
walked long distances to hunt and find food. Chasing wild animals with clubs,
climbing trees to collect nuts, and fleeing from predators were all part of daily
life. Constant migration was also a fact of early human existence. As a result of
this constant exercise, humans burned huge numbers of calories per day. This
primitive diet provided us with the essential protein needed to build muscles and
the natural fats we needed to promote satiety. The survival of early humans was
aided by a diet that balanced the fatstoring hormone (insulin) and the fat-burning
hormone (glucagon). When food was abundant, our ancestors ate lavishly. Then
the food was converted to saturated fat by insulin and stored to be used for
energy at a later time. When food was scarce, the stored fat would be converted
by the fat-burning hormone (glucagon) into sugar and used for energy. Insulin
and glucagon remain essential for our survival since they play a vital role in
energy storage and usage (Fig. 2.1) and were in perfect balance in this time
period.
Figure 2.1: Food Storage and Metabolism
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