Fasting vs. Eating Less: What’s the Difference? (Science of Fasting)

Fasting vs. Eating Less: What’s the Difference? (Science of Fasting)


“Breakfast of champions.” What’s the difference between eating less
food and eating no food? Well, Let’s look at two different situations. …In 1944, a study called the Minnesota Starvation
Experiment was conducted and was designed to understand the effects of caloric restriction
on the body in order to gain some knowledge that would help people starving in the aftermath
of World War 2. Thirty-six healthy men with an average height
of 178cm (about five foot ten) and average weight of 69.3 kilograms (or 153 pounds) were
selected. For three months, they ate a diet of 3200
calories per day. Then, for six months they ate only 1570 calories. However, caloric intake was adjusted to attempt
to have the men lose 1.1 kilograms per week, meaning some men got less than 1000 calories
per day. The foods given were high in carbohydrates-
things like potatoes, turnips, bread and macaroni. Meat and dairy products were rarely given. During the six months, the men experienced
profound physical and psychological changes. Everyone complained that they were too cold. One subject talked about having to wear a
sweater in July on a sunny day. The subjects’ body temperature dropped to
an average of 95.8 degrees Fahrenheit (35.4 degrees celsius). Physical endurance dropped by half, and strength
showed a 21 percent decrease. The men experienced a complete lack of interest
in everything except for food, which they were obsessed with. They were plagued with constant and intense
hunger. There were several cases of neurotic behavior
like hoarding cookbooks and utensils. Two participants had to be cut from the experiment
because they admitted to stealing and eating several raw turnips and taking scraps of food
from garbage cans. At first, the participants were allowed to
chew gum, until some of the men began chewing up to 40 packages a day. Now compare all this to the case of Angus
Barbieri, a Scottish man who in 1965 fasted for over 380 days straight. That is he took in no food whatsoever -nothing
but water, black coffee and straight tea for just over a year. He lost 276 pounds, going from from 456 pounds
to 180. A case report published by the Dundee University
Department of Medicine in 1973 said “…the patient remained symptom-free, felt well and
walked about normally,” and “Prolonged fasting in this patient had no ill-effects.” There were no complaints of mind numbing hunger
and he kept the weight off- for several years his weight stayed around 196 pounds. This of course is not a perfect comparison,
with the case of Angus, there’s only one subject and his starting weight was drastically
higher compared to those in the Minnesota Experiment. However, it does illustrate some very interesting
points about just how different of a physiological response you get from fasting (that is, eating
nothing) compared to eating less, or caloric restriction. Dr. Jason Fung, a Toronto physician specializing
in kidney disease, and author of the Obesity Code, says that compared to fasting, Caloric
Reduction will result in: less weight loss, more lean mass loss (i.e. more muscle loss),
and more hunger. Let’s start by talking about hunger. In Upton Sinclair’s 1911 book “The Fasting
Cure,” he writes about fasting as a means to improve health. In describing his first couple attempts at
fasting he writes “I was very hungry for the first day-the unwholesome, ravening sort
of hunger that all dyspeptics know. I had a little hunger the second morning,
and thereafter, to my great astonishment, no hunger whatever-no more interest in food
than if I had ever known the taste of it.” Sinclair recommends to do quite long fasts
– around 12 days or so. In a section addressing concerns about fasting
he writes “Several people have asked me if it would not be better for them to eat
very lightly instead of fasting, or to content themselves with fasts of two or three days
at frequent intervals. My reply to that is that I find it very much
harder to do that, because all the trouble in the fast occurs during the first two or
three days. It is during those days that you are hungry.” Then he says: “…perhaps, it might be a
good thing to eat very lightly of fruit, instead of taking an absolute fast-the only trouble
is that I cannot do it. Again and again I have tried, but always with
the same result: the light meals are just enough to keep me ravenously hungry…” In the book he says you will know when you
should finish fasting, because your hunger will “return.” He quotes a letter he received from a 72 year
old man saying “After fasting twenty-eight days I began to be hungry, and broke my fast
with a little grape juice, followed the next day with tomatoes, and later with vegetable
soup. ” He quotes several other letters he received
from readers and this disappearance and reappearance of hunger is a common theme. Everyone who wrote to him fasted for at least
10 days, saying they only broke their fast when hunger “returned.” This phenomenon runs contrary to the idea
one would get hungrier and hungrier as long as they don’t eat. However, most people have experienced for
themselves that this is not the case. Some will find that they are not hungry at
all in the morning or at least they are not as hungry as they are for lunch or dinner. But unless you are eating in your sleep, the
morning is when you have gone the longest without food. Some of this can be explained by the hormone
Ghrelin. Ghrelin, known as the “hunger hormone”
has been found to increase appetite and weight gain. A study at the Medical University of Vienna
looked at patients participating in a 33 hour fast. Their ghrelin levels were checked every 20
minutes. Here’s how the levels changed over time. What’s interesting is ghrelin is lowest
at 9:00AM, which is when they have gone the longest without eating. And, Ghrelin comes in waves and overall doesn’t
rise during the period the subjects were fasting. Then, As you can see, ghrelin rises in sync
with normal lunch and dinner times, as if the body had learned to expect food at that
time. However, that ghrelin rise spontaneously decreases
after 2 hours without food. I’ve experienced this kind of spontaneous
decrease in hunger myself many times when I was working as a consultant. Lunch time would come and I would be hungry,
but I was too busy to eat so I just kept working. Pretty quickly I forgot about eating and wasn’t
particularly hungry until dinner time. This is very helpful to keep in mind if you’re
doing a long fast or even if you’re starting intermittent fasting – you’re going to get
annoying waves of hunger, especially around the times that you usually eat. But, it won’t get worse, the hunger will
simply go away if you are patient. Another study concerning ghrelin was done
at Aarhus University Hospital in Denmark and it shows what happens if you do a longer fast. They looked at the ghrelin levels of 33 subjects
who fasted for 84 hours. So, did they get increasingly hungrier throughout
the fasting period? Well, No. Their ghrelin followed similar rhythms each
day but actually decreased the longer they fasted. Going longer without food actually made them
less hungry. This gives credence to what Upton Sinclair
and his readers said about hunger disappearing after the first 3 days of fasting. I’ve done a couple 5 and 6 day fasts in
the past myself and this was indeed the case. Actually, I did a 4 day fast last week and
again the 4th day was when I had the least hunger. Another thing that may be contributing to
this phenomenon is that you are entering ketosis. Ketosis is a physiological state where your
metabolism switches to using primarily fat for energy. For this reason ketosis is popular as a weight
loss method, but it has many other benefits including better physical and mental efficiency. Ketosis occurs when you restrict carbohydrates
down to 50 grams or less and you don’t eat too much protein. Everyone’s body is a bit different so you
might have to eat even less carbohydrate or may have room for more, but the recommended
ratio of a ketogenic diet is to get 5% of your calories from carbs, 25% from protein
and 75% from good fat. A simpler way to enter ketosis is just don’t
eat anything for a long enough time. This is one of the major points in the difference
between fasting and caloric restriction. The problem with the subjects in the Minnesota
Starvation experiment was that they were eating just enough to keep them out ketosis and keep
their metabolism primed for burning carbohydrate (glucose), so they couldn’t use their body
fat for energy. This explains a lot of things like why they
were losing their strength and were very sluggish and cold. It also clears up why Upton Sinclair said
fruit or light meals were just enough to keep him ravenously hungry and far weaker than
if he had just eaten nothing. As I explained in my last video, insulin is
necessary for glucose to get into the cell to be used for energy. When you eat carbohydrates, the pancreas secretes
insulin to deal with it and too much insulin hampers the action of something called hormone
sensitive lipase which is necessary to mobilize fat and use it for fuel. Though, keep in mind that grains or refined
carbohydrates will provoke a much higher insulin response than say green vegetables. Now because the body is having a hard time
using its fat for fuel, it will do a couple things: One, it will simply slow down metabolism
to preserve energy. In the Minnesota Starvation experiment, the
subjects metabolism dropped by 40 percent. Their bodies didn’t have access to its stored
energy, and their restricted calorie diets don’t provide much fuel so there’s no
choice but to slow down the metabolism. Ironically, in the case of fasting, as Jason
Fung points out – metabolism actually goes up. “If you don’t do anything about your insulin
and just reduce your calories, your metabolism goes down. But what happens during fasting? Well, here’s a study of 4 consecutive days
of fasting. What happens to your REE – this is this middle
line here, that’s the resting energy expenditure. It doesn’t go down, it goes up. You’re burning more energy than you did.” The other thing the body will do when it can’t
use fat for fuel is break down muscle into glucose through a process called gluconeogenesis. The body doesn’t want do this too much because
it’s not very smart to completely eat through something as important as muscle, but when
it can’t access its own stored energy it’s more likely to resort to this. This is why you’ll experience more muscle
loss on caloric restriction than if you ate nothing. When you are fasting, Human Growth Hormone
is released. As the name implies, Human Growth Hormone
is an anabolic hormone – a hormone conducive to growth. In Leningher’s Principles of Biochemistry
textbook they give the example of how injecting the human growth hormone gene into a mouse
makes it unusually large. As explained in Guyton’s Textbook of Medical
Physiology: “…growth hormone also mobilizes large quantities of free fatty acids from
the adipose tissue, and these in turn are used to supply most of the energy for the
body cells, thus acting as a potent “protein sparer.” “That is human growth hormone is protecting
your muscles from breaking down. The study I referred to earlier about subjects
undergoing an 84 hour fast shows that growth hormone rises significantly after the second
day of fasting. As mentioned earlier, you should enter ketosis
sometime within the first 3 days or so of fasting, and it depends on how much you are
moving around and what your diet was like before starting the fast. The state of ketosis is a great indicator
that your body is making good use of its stored body fat for energy. In Tim Ferriss’ book “Tools of Titans,”
Tim talks about his first clinically supervised 7 day fast. For some sort of liability reasons, he wasn’t
allowed to exercise or leave the facility. Considering exercise is a potent stimulator
of human growth hormone and will help deplete glucose stores, not getting any exercise is
a great way to prevent yourself from getting into ketosis during a fast. It’s also a great way to lose muscle. Tim says he lost 12 pounds of muscle during
the overly restrictive clinically supervised 7 day fast. But, when following a protocol designed to
get him into ketosis as soon as possible – involving things like 4 hours of brisk walking, he did
a ten day fast and apparently lost zero muscle mass. One last factor in Ketosis preserving muscle
is leucine. When you’re in ketosis, you have a higher
fasting blood leucine level. And leucine is a key branch chain amino acid
that has an anabolic effect on the body so it preserves lean body mass. A lot of people interested in building muscle
may be worried that fasting or a ketogenic diet wouldn’t work for them because insulin
and therefore carbohydrates are necessary for protein synthesis (i.e. muscle growth),
but actually this leucine fills that role and is a good trigger for protein synthesis. So, just to sum all this up: compared to a
conventional calorie restricted diet, fasting means you lose more weight in the form of
fat, you keep more muscle, you have more energy, and you are less hungry . If proper weight
loss is your goal, it might be better to eat nothing at all rather than eating a conventional
low calorie diet.

100 thoughts on “Fasting vs. Eating Less: What’s the Difference? (Science of Fasting)

  1. Just in case I should also say that of course you need to balance fasting with eating – You need to survive off of something. I have been doing intermittent fasting the past year (22 hours fasted, 2 hours eating – you can widen it to 16/8, which still provides great benefits) and will fast for a couple days every other month or so. Several other people have recommend a routine like this – Tim Ferriss recommends doing a 3 day fast once per month and a 7 day fast once per year.

  2. So I quess people from the past, who lived and died during famine times just didn’t knew how lucky they were to have the chance to be fasting and how beneficial the fasting was for their health. What a waste, they didn’t knew about ketosis and the benefits of not eating anything at all for a long time.

  3. Eat whenever you are hungry. Don't eat too much! The more you eat then the more workout you need to do! Fasting? Do it when you are sleeping!

  4. Can you share/make video on how many hours should we fast and what kind of food and drinks we should indulge in after breaking fast?

  5. honestly i came here for a yes or no answer not the history of fasting. putting your self in a calroic deficite . does it work or not thats all i want to know , this is one of the most useless videos out there

  6. Can I fast if I'm skinny? I have thyroid issues and weigh 99lbs. I was thinking of fasting 2 days a week and eating 2 meals a day for the other days ( I don't like breakfast ). And what is the difference between long term fasting and anorexia?

  7. People who have been lost for four or more days that had access to water, many of them were found dead. Many studies show you will die if you do not eat for four or more days. What the makers of this video are not stating is that the definition of fasting to which the people in this video are referring is extremely light eating days, water, carrots, celery sticks and the like. Unless you have considerable body fat and you go more than four days without eating, your bowels will turn on you and attempt to devour themselves, which causes EXTREME pain. Do not listen to these clowns. Fasting for 24 to even 48 hours can be safe. Anything more than that puts you at ever increasing and fatal risks.

  8. What is the point in even citing a study on caloric restrictions that is 80 years old when there have been numerous studies done recently? One must ask themselves why this was done

  9. ok but it’s okay to also enjoy stuff and have a little bit of fun!! have some fries or fresh baked cookies once in a while!!!!!!

  10. The problem is I love fasting but because you're not taking in protein if I workout extremely hard twice a week and I try to eat as few times as possible I feel like my muscles aren't going to recover enough

  11. I suppose that is exactly why I wake up hungry if I eat right before going to bed, opposed to waking up not hungry when I don't eat before bedtime. Amazing! I've wondered for years why this happened.

  12. Using the fasting strategy to quit smoking worked very well for me. It worked the same too, where I'd get hungry and it would soon pass, same as wanting to go smoke but I would resist and it would soon pass.

  13. Did 3 days without eating, just black coffee, water and unsweetened tea. Aside from craving certain types of foods and the occasional hunger impulse, I noticed no ill effects. In fact, my focus at work improved, as did my overall energy for the day.

  14. Very interesting indeed..I’m 2 days into a 5 day water fast & have been really amazed i feel great..I don’t feel hungry at all? Walked 5 miles today no side effects, couple of hunger pangs at tea time but quickly passed with some water. Was looking around for why this might be when I found your video-great content thanks for helping me better understand this strange experience. I was expecting to feel ‘starving’ as on calorie restriction but nothing yet!

  15. i was upset with myself for not keeping it up with a healthy diet, then remembered that fasting is the solution for all my problems rn, if i don't forget, I'll post my results here.

  16. I fast for 12 – 16 hours every single day. It's the easiest thing on earth. I have no idea why people cry too much about no eating. Exactly today I had breakfast at 10:00 am (went to the gym fasted, I do extremely heavy lifting) after 16 hours without eating. Plus, my absolute monster breakfast tastes better after 14 hours of fast, plus 2 hours of weight lifting. It's 2,000 calorie dense. Tastes like heaven.

  17. I was watching this to motivate me during y fast. All those pictures of bread were torture! I love bread so much lol!

  18. Due to my lifestyle, i was gaining too much fat due to unbalanced sleep patterns. I still have those disturbances but a friend of mine helped me and put me in a more or less kitosis, paired with a carb Nite aproach (as i am a conventional amatour bodybuilder) where every 7 days i would binge on sugar, carbs and whatever i felt i needed to fill my muscles with glycogen.
    Again, after some research of my own, i found a training method called "Ponto Zero", translated would be something like "Point zero" or "starting point" by Fernando Sardinha, brazilian bodybuilder very well respected.
    All this to say that ive lost 20kg of fat in 1 year and my muscle mass is continuously going up. I think i found what works for me. Took 8 months of research and finding the right macro intake at a weakly basis and the right method for me.
    Its 2 am, im lucky if i get 2h sleep for my next shift as a flight attendant where ill be fasting till 10 am or so.. pays off…

  19. This was very informative and I will be attempting it. I tried to go 18 hrs without eating and made it to 17 hrs. It was hard for me. I feel very hungry. Here are some things I learned:
    1. Coffee is acid producing so having coffee before starting your diet will produce acidity and hunger. Green tea is soothing, no stomach rumbles from too much acidity. Acidity can lead to ulcers, so careful.

    2. Vit C powder mixed in water, or parsley tea will rid the body of toxins faster. Flushes them out. Less headaches, dizziness. Just a pinch several times a day. It is an acid so too much may cause stomach ulcers on an empty stomach. Parsley tea has high levels of Vit C.

  20. Dude it's all explained because you get into ketosis with little carbs. U don't don't we're t hungry in ketosis. Break a fast with high fats no carbs and u won't get hungry

  21. Ok, but you haven't said anything about the dizziness, and headaches that come long fast, did it almost 9 days but had to eat not because I was hungry, but because it was making me sick.

  22. You say of fasting for days…but after how many days. One should star eating again?and what eating routine should one follow then ?? intermittent fasting or keto diet or what? And when again one should go for the next fasting again? please reply.

  23. Im just curious, seen as carbs cause insulin to be released, but max 500kcal is considered to be so little that its still within the fasting radar, at least in nutrition studies. Would, lets say 500kcal worth of apples(which are high in carbs mainly natural sugars), still break a fast?

  24. Im a fan of Intermitent Fasting but honestly this is bunk not only is the one sample size an individual but an individual who was extrmely overweight compared to people of average to lean size I mean….

  25. I've been putting the food in my keyskr and found that you absorb food much more efficiently that's just hard washing it down with water and it really saves on toothpaste teeth are always White never need mouthwash

  26. started with a 8 hr fast, then 12, then 16 and now I'm eating once a day
    i feel more sharp, relaxed, less anxious , and less hungry and once a week I eat whatever i want . so far 35 lbs down

  27. I’m currently doing a low carb, high protein, high fat diet. I eat roughly the same ratio of fat and protein and a very low amount of carbs. If I’m eating a higher protein content am I still able to reach ketosis? And if not, is it unhealthy to prime my body to run on a high protein diet?

  28. Why is it that i have headaches and become lightheaded if i just miss breakfast ? Im not overweight or anything either, but if i skip a meal i will feel horrible.

  29. Did this a couple of months ago and it help me control my hunger, I always craved for sugar or tasty food, then I didn't even want to see it. I stopped because my family made me breakfast but now I will go back to it

  30. I fasted for three days not long ago. The entire time I was freezing even when I walked outside in 90 degree weather.

  31. I've only been eating one meal 4 hours before bed every day for a week and I'm still getting severe stomach cramps. Is this normal? Should I keep pushing?

  32. I just count calories, it's easy and it always works.. I just fast for 12 hours and comfortably eat for 12 hours.. Much easier than a strict fasting routine.

  33. I fasted for 24 days and never thought about food after the third day. The first day is brutal, everything temps you, but day two is easier and day three is less so. By day 20 or so, my mind worked more efficiently than I have never been able to replicate. Started at 350lbs ended at 275.

  34. Considering fasting but concerned about protein intake if I continue to pursue my weight training regime. Could I still have a protein shake but still remain on the fasting path?

  35. There is a contradiction in the video. If your calories intake is lower than you burn – that's caloric restriction. Bad. If you eat more than you burn – excess is stored as fat/glycogen. Bad too.

  36. Intermittent fasting works for weight loss. One nutrient dense meal a day, no snacking. It’s the only way I can lose weight. It works!!!! Plus, fasting helps your immune system. If you fast long enough, it reboots your immune system. I have an autoimmune condition, and after a complete fast for 24 hours, I feel much better.

  37. I was going to ignore this video even though it came up in autoplay/recommends…. glad I watched. You put a lot of interesting diet stuff in here in just twelve minutes. I didn't like the movie clips, but who cares, haha.

  38. Getting down to low body fat is harder than maintaining it. I never understood what it meant to be really hungry until 8% bodyfat. My dick also stopped working.

  39. I will never understand all this…I am 64 years old…I weigh the same as when I was 18years old.I never …and I mean never..buy fast food…I dont eat sweets or chocIates.. eat healthy food…that I prepare myself and I train 6days a week.Sounds boring…no !!..this is what work for me.I am the healthiest person I know….so far!🤣🤣

  40. To save some people time to have a more satisfying life just try to cut some things out of your diet. You don't have to eat so much or so little, that's not how to do this.

    Focus on clean and pure food like lean meat, steamed fish, steamed veggies without seasoning. Go easy on the carbs and eat less sugar. 1 or 2 alcoholic drinks are fine.

    Enjoy things at a medium and you'll feel better.

  41. I dare anyone go week without ANY food. You'll faint and gonna be so weak that almost unable to walk. This video is dumb af.

  42. Less starchy food and 🍞. Low carb diets pretty much is the consumption of veggies and fruits. Cut sugar out (except fruits and veggies) bam there ya go, you won't be over weight but now it's up 2 u on how you want to look as far as physique.

  43. 18 MONTHS 7 DAYS A WEEK USING 18 – 6 – WENT FROM 220 TO 185 AND HAVE KEPT IN FOR 7 MONTHS – NO DIET – i EAT AND DRINK NORMALLY DURING MY 6 HOURS….

  44. What has worked for me was I ate one healthy meal a day cut out sugar for over a week except fruits and exercised and drank water…. fat melted off me

  45. waht weak men. ive been on a 1300 kcal a day diet for exactly 3 months today, lost 50 lbs. im on a high fat low carb diet though.

  46. I eat like a king Monday through Saturday, and then fast on Sundays. I feel great. I hit the weights and get a calorie surplus for most days, but then rest on the weekend (and fast on Sunday) which is preventing me from packing on a bunch of fat. I've been getting consistently stronger and look and feel better since I started this about 2 months ago.

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