Fasting vs caloric restriction

(Doing a Mediterranean Keto) #1

I am doing a keto caloric restriction for 2nd time. First time it worked very well. Now it is working very well again. I am at 79.15kg, so I would say I am at around 4kg of my ideal weight.

PSMF is basically caloric restriction. For me, it works very well. But I know most people here argue for eating to satiety, or IF or fasting.

But for me, none of those works (I have tried). But a PSMF, keto calorie restriction diet makes wonders to me.

My question is: could a caloric restriction diet “mimic” fasting?

From comments, it seems that people distinguish a lot between fasting and eating little. It seems that the last mile (not eating anything) is what really provides health and longevity benefits.

But in my case, I feel very well with this caloric restriction. And being a scientist, it is difficult for me to accept that if you are at 2 in a scale from 0 to 10, you are gaining nothing, and you really need to go to 0 instead. Usually, 2 is better than 4, which is better than 6 which is better than 8. And the jump from one to the other is more or less proportional.

But from reading about fasting, it seems as if this is not the case. That one needs perfection in fasting (i.e. not eating anything at all) in order to reap the benefits.

Is there any idea here about this topic?

(Bob M) #2

I think it’s at best unclear. As we used to say in rural PA, “as clear as mud”.

A PSMF is really a calorie-restricted, but typically also time-restricted eating, method. So, you eat say 500 calories but only in one meal on certain days. But since no one has actually defined a PSMF, it comes in many forms.

The purported benefits to fasting are an increase in growth hormone (at some point), and modifications of other hormones. I find this to be true, personally.

I also find it very difficult to eat small amounts of calories per day.

But I think if you’re getting results from calorie restriction and not from fasting, then you should do what gets you results.

(Michael - When reality fails to meet expectations, the problem is not reality.) #3

For what it’s worth, which may be not much, my n=1 was this. I started keto not primarily to lose weight but since I had some of excess I thought ‘why not?’ I had zero idea what I was doing at the time other than not eating carbs. I thought I had to restrict overall calories to lose the weight because I’ve been hearing that mantra all my life. I guessed my daily caloric requirement was about 1800 cals so decided to limit calories ‘modestly’ to 1500 per day.

For 3 months I ate bog standard keto with a fat:protein gram ratio of about 1.5:1 and sub-20 grams of carbs per day. During those first 3 months I lost 25 pounds. I decided it was time to return to ‘normal’ so starting upping my daily calories by a couple hundred or so every couple of weeks. It took another 3 months to stop the loss! By that time I was eating 2500 calories per day. So for 3 months I was eating a 1000 cal per day deficit. For an additional 3 months a gradually decreasing deficit until my weight stablized at 145. My original target had been 150. I’ve maintained 144-5 for nearly 4 1/2 years still eating bog standard keto, sub-20 grams of carbs and doing my easy peasy overnight IF 3 or 4 times per week depending on my work schedule.

The biggest concern I read about is that restricting calories leads to metabolic slowdown. Yes, I’ve read the ‘Biggest Loser’ followup study and much else. For me, it did not. At least for 6 months. Maybe for folks with more severe metabolic issues or who restrict calories for much longer times it does to compensate for the lower energy input. But for at least some of us a relatively brief interlude does not. Please note, which I think is fairly significant, that I continued to lose weight as I gradually increased my energy intake over the course of 3 months. So my metabolism responded normally and I think indicated a healthy response to varying energy intake.


If it’s about losing fat, it’s all about calories for me and many others. I surely would lose fat wonderfully on PSMF, I just rather stay fat than torture myself that severely… :slight_smile: It’s not for me. I just can’t eat so tiny meals without getting hungry in 1 hour in the rare cases when it doesn’t make me very hungry right away.
Fasting, not eating anything, that’s way, way, way easier. At least in the first 19-24 hours when I am wonderfully satiated…

I am with you at that. Though I consider eating nothing better than little to some level, the body is in peace and can do autophagy whatever that is… But it matters how long term it is and after a few days, I think both are unhealthy and muscle eating… No fasters can persuade me that the body just keeps the muscles and the usual metabolism for many days with 0 protein intake. 1-2 days sound believable.
And I am aware I may be a bit biased as my body throws a huge temper tantrum in low-cal days so they won’t be low-cal days in the end… For certain people low-cal days in some pattern may be the best method. I don’t get it but too many people says so :smiley: Maybe their low-cal days really have some tiny disadvantages for the body but they can deal with it and there is nothing better for them.

But there are so many we don’t even know. I’ve read about so many things in fasting threads in my life and a lot of things are mysterious.

I am very sure long term undereating is bad, I don’t list the problems now, probably everyone knows the main points. But having low-cal days smartly… That may be okay for some. Not for me. I had a few low-fat and a few low-cal days in my whole life and not under normal circumstances.
But you are not me, quite obviously :smiley: If it works for you, great! I typically did the right thing ignoring advice as they typically aren’t for my individual case. I tried out promising things but sometimes I knew it would be a bad idea for me.

(Take time to smell the bacon) #5

According to Dr. Jason Fung, a Canadian nephrologist who uses fasting to treat his patients, the body responds differently to caloric restriction, from how it does to fasting. He maintains that our ancestors’ normal eating pattern was a cycle of feasting and fasting, so the body considers going without food to be normal, whereas an inadequate caloric intake is the signal to the body that we are in a famine.

People do challenge some of Dr. Fung’s advice, but it is certainly true that many members of these forums have reported that their fat loss did not start until they stopped restricting calories and ate more.

The science writer Gary Taubes has said that he thinks “eat less, move more” works for quite a few people, but that there are many more people for whom it does not. He also believes he sees a pattern of thin obesity researchers using the mantra to shame obese people as being gluttons and sloths.

I guess what it all comes down to is knowing your own body.

(Robin) #6

As you see, our answers are all over the place. I limit my hours of eating to 11-5. But only cuz I’m not hungry till then and I sleep better with no snacking past dinner. I think it depends on you… with calories too. You seem to have found what works and you may tweak it or you may stay in the groove. Either way, you got this!


some info to read and maybe help?
you don’t have to buy anything LOL there is tons to read here.


Yes an no, A PSMF is very calorie restricted, typically around 800-1000cals and it’s pretty much all protein and green veggies, no carbs, no fat that doesn’t absolutely need to come it with other things. PSMF’s work amazing for fat loss, downside is for many they make you ravenously hungry, where an actual fasts don’t in many cases. Upside it you’re still eating and you preserve muscle mass.

People do different things, and while technically there is no “official” way to do a PSMF, UN-officially most people doing PSMFs are following it as made popular by Lyle McDonald from his Rapid Fat Loss Handbook.

I’m no longer a fan of fasting at all thanks to my metabolic slowdown and loss of muscle mass, I still do PSMFs though and have had no issues from them.