One might ask, what about avoiding the fructose in fruit? Fruit is a healthy food
because, in nature, fructose is packaged with fiber—a component of food that Lustig
calls half the antidote to the fructose effect and the obesity pandemic. The other
half of the antidote is physical activity. Fiber is not digested, and except for
the extent it is broken down by gut bacteria, it is not used for energy by humans (it
is food for herbivores). Fiber makes an important contribution to our health. One
type, soluble fiber, is found in oatmeal, lentils, carrots, and many fruits. With the
addition of water, it becomes a viscous mass in the digestive tract that slows the
digestion and absorption of food. It also binds to bile acids and helps lower blood

Insoluble fiber is found in whole grains, seeds, nuts, brown rice, and
many vegetables. In contrast to soluble fiber, it speeds the passage of foods through the small and large
intestines. This means that food moves through the small intestine with alacrity and
more quickly generates the PYY signal that tells the brain, “I’m full.” Waiting for
the PYY signal to kick in is why it is advisable to wait 20 minutes before going for
seconds. Insoluble fiber can shorten this wait, and if you wait, you may more easily
be able to go without second helpings or a dessert.

There is evidence that humans evolved eating, and hunter-gathers still eat, hundreds
of grams of fiber a day. It can be argued that human physiology is adapted
to eating large amounts of plants that are abundant in fiber. The recommended
standard of 14 grams of fiber per thousand calories, or about 25 grams per day for
women and 38 grams per day for men, is not set very high, but it is not met by 97%
of Americans. One reason is that prominent components of the typical American
diet, such as meat and cheese, do not contain fiber.

Plant-based high fiber foods are less energy-dense, so you get fewer calories for
the same quantity of food. Fiber-rich foods require more chewing, slow down eating,
and when your stomach is full, it contains fewer calories when the “I’m full”
signals are sent to your brain. Slowing digestion activates what is called the ileal
brake—the feeling of fullness that is sent to your brain when undigested food makes
is down to the last part of the small intestine, the ileum. Fiber cuts appetite another
way. The bacteria in our guts turn fiber into short-chain fatty acids that reduce inflammation
and stimulate the production of the leptin that signals the brain to reduce
our appetite.

Another benefit of fiber is that when the two kinds of fiber work together to slow
digestion, this limits the rapid rise of glucose and attenuates the magnitude of the
insulin response. Milling grain to make white flour, white rice, pasta, and breakfast
cereal strips out about three-quarters of the fiber and makes these foods more rapidly
digestible. These refined foods cause a more rapid increase and higher peak
concentration of glucose that the liver has to cope with. In contrast, the consumption
of high levels of insoluble fiber decreases insulin resistance. Fruit is a healthy
food because it comes with fiber. Destroying insoluble fiber by juicing fruit, or even
worse, just drinking plain juice or a sugar-sweetened soft drink, slugs the liver even
harder with high concentrations of the fructose and glucose that stimulates the high
levels of insulin that lead to obesity. To get the benefits of fiber is one important
reason to avoid most processed foods. Skip the juice and eat whole or minimally
refined foods.

This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel.