Welcome to the Nutrition Facts Podcast. I’m your host Dr. Michael Greger.
The coronavirus pandemic has made many of us very aware
of the importance of maintaining and improving our health.
Make that your silver living.
Because the more positive change we can make to our diet and lifestyle, the better.
There have been a lot of studies that have come out recently about fasting.
In fact – I did a whole series on fasting recently.
And here are two more studies –
to add to our understanding.
We start off today with a study on the origins of therapeutic fasting.
The story of life on earth is a story of starvation.
Ash from massive volcanoes and asteroids block out the sun,
killing the plants, which then killed most everything else.
As Darwin pointed out though, from this “war of nature,
from famine and death, the most exalted object that we
are capable of conceiving” arose—namely us.
We are “particularly well adapted to prolonged fasting.”
Evolving in a context of scarcity is believed to have shaped
our exceptional ability to store
large amounts of calories when food is available.
Of course, now our ability to easily pack on the pounds
is leading to modern diseases like obesity and type 2 diabetes,
but without the ability to store so much body fat
we may not have made it to tell the tale.
And it’s not just asteroids millions of years ago.
“All of Upper Egypt was dying of hunger,” reads an inscription
on an Egyptian tomb from about 4,000 years ago,
“to such a degree that everyone had come to eating his children...”
Or, just hundreds of years ago –
parents killed their children and children killed their parents
and ate them; "the bodies of executed criminals
were eagerly snatched from the gallows.”
Wiping out as many as two-thirds of the population of Italy,
one-third of the population of Paris.
So, we don’t have to go back to ancient history.
Even the most secure and affluent populations of today
need only trace their history back a short distance.
For example, nearly 200 famines in Britain
over the last 2,000 years.
Now, we tend to be suffering from too much food,
which carries its own problems, but might there be
any negative consequences to not ever starving?
This was a question raised 50 years ago.
I mean, if our physiology is so well-tuned to periodic starvation,
maybe by eliminating that we may be doing harm to our overall well-being?
We just didn’t know.
The lack of research in the area of starvation was attributed
to the “difficulty of securing willing human subjects."
So, what little we had came from unwilling subjects.
Physicians within the Warsaw Ghetto made detailed accounts
before they themselves succumbed; or Irish Republican prisoners
starving themselves to death after up to 73 days on hunger strike.
But starvation isn’t necessarily the same as fasting,
an issue raised in medical journals over a century ago.
Starvation is normally a forced, mentally stressful,
and chronic condition, whereas therapeutic fasting is voluntary,
limited in duration, and usually practiced by people
who start out with adequate nutrition.”
Therapeutic fasting?
Where did we get this idea of fasting therapy,
fasting for medical purposes?
It may have originally arose out of the observation
that when people get acutely ill they tend to lose their appetite;
so, maybe there’s something in the body’s wisdom to stopping eating.
That’s presumably where the whole “starve a fever” folklore came from.
There was this sense that fasting affords physiological rest for the body,
not just the digestive tract, but throughout,
allowing the body to concentrate on healing.
It was evidently an open secret that veterinarians
used to hospitalize dogs only to fast them back to health;
and so maybe, the theory went, it might work for people too.
Beyond just freeing up all the resources that would normally
be used for nutrient digestion and storage,
there’s this concept that during fasting our cells
switch over to some sort of protection mode.
Why would fasting reduce free radical damage and
inflammation and bolster cellular protection?
It’s the that-which-doesn’t-kill- us-makes-us-stronger concept
known as hormesis.
So, that’s kind of the opposite of the let-the-body-rest theory.
It’s more like let-the-body-stress.
The stress of fasting may steel the body against
other stresses coming your way.
This was demonstrated perhaps most starkly in a set of cringe-worthy
experiments in which mice were blasted with Hiroshima-level
gamma radiation sufficient to kill 50% within two weeks,
but of the mice who had first been intermittently fasted
for six weeks before, not a single one died.
It’s this kind of dramatic data that led to extraordinary claims,
like therapeutic fasting could drive half of all doctors out of business.
But you don’t know, until you put it to the test, which we’ll explore next.
A century ago, fasting—starvation as a therapeutic measure—
was described as the ideal measure for obesity.
As you can see, fat shaming is not a new invention in the medical literature.
I've extensively covered fasting for weight loss in a nine-video series
starting with this one, but what about all the other purported benefits?
I do have a video series on fasting for hypertension, but what about psoriasis,
eczema, type 2 diabetes, lupus, metabolic disorder, rheumatoid arthritis
and other autoimmune disorders, depression, anxiety?
Why hasn't it been tested more?
One difficulty with fasting research is what do you mean by fasting?
When I think fasting, I think of water-only fasting, but in Europe
they tend to practice so-called modified fasting, or Buchinger fasting,
which is more like very low-calorie juice fasting with some vegetable broth.
Some forms of fasting may not even cut calories at all.
Ramadan fasting is when devout Muslims abstain from food and drink
from sunrise to sunset, yet interestingly, they end up
eating the same amount, or even more food, overall.
The largest study on fasting to date was published in 2019.
More than a thousand individuals were put through a modified fast,
cutting intake down to about 10 cups of water, a cup of fruit juice,
and a cup of vegetable soup a day.
They reported very few side effects, which is in contrast to the latest
water-only fasting data, which only involved half as many people
but reported nearly 6,000 adverse effects.
Now the modified fasting study did seem to try to undercount adverse effects,
only counting reported symptoms if they were repeated three times,
but still only reporting single cases of things like nausea, feeling faint,
upset stomach, vomiting, or palpitations, whereas the water-only fasting study
reported about one to two hundred of each. What about the benefits though?
In the modified fasting study, participants self-reported improvements
in physical and emotional well-being, along with a surprising lack of hunger.
And the vast majority of those who came in with a pre-existing health complaint
reported feeling better, with less than 10% reporting
their condition worsening or remaining unchanged.
They weren't just fasted though, but engaged in a lifestyle program,
which included being placed before and after on a plant-based diet.
Too bad they didn't have some people just do the healthier diet
without the fast to tease out the fasting effects. Oh, but they did!
About a thousand folks fasted for a week on the same juice
and vegetable soup regimen versus those put on normocaloric,
meaning normal calorie, vegetarian diet the whole time.
Both experienced significant increases in both physical
and mental quality of life, and interestingly there was
no significant difference between the groups.
In terms of their major health complaints—rheumatoid arthritis,
chronic pain syndromes like osteoarthritis, fibromyalgia, and
back pain, inflammatory and irritable bowel disease,
chronic pulmonary diseases, and migraine and chronic tension
headaches—the fasting group appeared to have an edge,
but both groups did good, with about 80% reporting
improvements in their condition, with only about 4% feeling worse.
Now, this was not a randomized study;
people chose which treatment they wanted.
So maybe, for example, those choosing fasting were sicker or something.
The improvements in quality of life and disease status were also
all subjective self-report, which is ripe for placebo effects,
no do-nothing control group, and the response rates to the follow-up
quality of life surveys were only about 60 or 70%,
which also could have biased the results. But extended benefits are
certainly possible, given they all tended to improve their diets.
More fruits and vegetables, less meats and sweets,
and therein may lie the secret. Principally, the experience of fasting
may support motivation for lifestyle change. Most fasters
experience clarity of mind and a feeling of letting go of past actions and
experiences, and thus may develop a more positive attitude towards the future.
As a consensus panel of fasting experts concluded:
nutritional therapy is a vital and integral component of any fasting.
After the fasting therapy and refeeding period, nutrition should
follow the recommendations of a plant-based whole-food diet.
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