insulin levels get. It also depends critically upon how long those
insulin levels stay up for. That’s why it’s so important to allow periods
when insulin levels are allowed to drift downwards. Fasting (When to
Eat) addresses the second half of the problem. Fasting corrects some of
the hormonal problems that cause obesity and so helps maintain long-
term weight loss. Combining the proper diet with intermittent fasting is
a time-tested weight-maintenance method.
What does that mean? Suppose you spend $1,000 in one day. That’s
a fantastic shopping day. If this happens only once a year, that’s accept-
able. However, if it happens every single day, you will soon be very poor.
So, the total effect depends not only upon the level but also the duration
and frequency of the activity. Insulin is no different. The total insu-
lin effect depends not only upon how high insulin levels get (which
depends upon the foods we choose to eat), but also upon how persistent
those high insulin levels are. This depends upon how often you eat,
which is an entirely different issue than which foods we choose to eat. If
you are trying to lose weight, an insulin spike once or twice a day is far
preferable to multiple spikes per day.
How can we induce our body into a temporary state of very low insu-
lin levels? Because all foods raise insulin, the only way for us to lower it
is to completely abstain from eating. The answer we are looking for is, in
a word, fasting. Fasting refers to any period in which you do not eat. This
may be several hours (between meals) or several weeks. For weight loss
and a reversal of type 2 diabetes, I commonly recommend intermittent
fasts of sixteen to thirty-six hours.
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introduction
Fasting is one of the oldest remedies in history, but it is not to be
confused with starvation, which is a notably unhealthy state. Starvation
is involuntary abstinence from food; it is neither deliberate nor con-
trolled. If you have not eaten for a while, and have no idea when you will
eat again, you are starving. By contrast, fasting is voluntary abstinence
from food for spiritual, health, or other reasons. You may fast as long as
you like, but you can always decide to eat again, if you like.
People often worry that if they don’t eat, they’ll have less energy
and they won’t be able to concentrate as well, but that’s simply not true.
Think about the last time you ate a huge meal—for example, at Thanks-
giving. Did you feel more energetic and mentally alert afterward? Or did
you feel sleepy and a little dopey? More likely the latter. Eating shunts
blood to your digestive system to cope with the huge influx of food, leav-
ing less blood for brain function. Fasting does the opposite, meaning
there’s more blood for your brain. The human body has adapted to func-
tion and thrive in the temporary absence of food.
Glucose and fat are our main sources of energy. When glucose is not
available, the body adjusts by using fat. Fat is simply our stored food
energy. That’s what it’s designed for. In times of food scarcity, stored food
(fat) is naturally released to fuel our bodies. That’s entirely normal. The
transition from the fed state to the fasted state occurs in several stages:
1. Feeding: During meals, insulin levels go up, allowing glucose uptake
by tissues such as the muscles or brain for direct use as energy. Excess
glucose is stored as glycogen in the liver.
2. The post-absorptive phase (six to twenty-four hours after fasting
starts)
: Insulin levels fall. The breakdown of liver glycogen releases
glucose for energy. Glycogen stores last for roughly twenty-four hours.
3. Gluconeogenesis (twenty-four hours to two days): The liver manu-
factures new glucose from amino acids and glycerol. In people who
do not have diabetes, glucose levels fall but stay within the normal
range.
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THE OBESITY CODE COOKBOOK
4. Ketosis (one to three days after fasting starts): The storage form of
fat, triglycerides, is broken into the glycerol backbone and three fatty
acid chains. Glycerol is used for gluconeogenesis. Fatty acids may
be used directly for energy by many tissues in the body, but not the
brain. Ketone bodies, capable of crossing the blood-brain barrier, are
produced from fatty acids for use by the brain. Ketones can supply up
to 75 percent of the energy used by the brain.
5. Protein conservation phase (after five days): High levels of growth
hormone maintain muscle mass and lean tissues. The energy
required to maintain basal metabolism is almost entirely produced
by available free fatty acids and ketones. Increased norepinephrine
(adrenalin) levels prevent a decrease in metabolic rate.
With fasting periods of sixteen to thirty-six hours, blood glucose
