Alternate Day Fasting Effects on Non-Obese Adults

(Joey) #1

Came across this study (published back in 2005) on alternate day fasting by non-obese adults. The general pattern was for subjects to refrain from eating for 24 hours and then eat twice as much “as normal” for the next 24 hours. This went on for 3 weeks.

I found this interesting since those of us who are pretty lean often wonder whether fasting (IF or EF) will do more good than harm - e.g., balancing the potential for enhancing autophagy against the risk of lowering one’s resting metabolic rate below current levels.

While the authors suggest that alternative day fasting may be good for extending life (a question in NO way addressed within the study itself), the alternate day feasting/fasting cycle did measurably reduce resting metabolic rate (RMR) - from a baseline of 6675 kJ/d to about 6300 kJ/d (men and women had slightly different, although similar reductions).

Importantly, the authors also note that the “hunger” and “irritation” that participants almost universally experienced on their fasting days did not abate after 3 weeks of compliance with the study protocol. As such, they concluded this was not likely an eating pattern that would work well for non-obese folks over time.

One significant shortcoming of this study is that it did not specify what the subjects actually ate on their feast days. They were instructed to eat “whatever the wished” and no further info was provided. It’s reasonable to assume that, since the study was done at Louisiana State University, most if not all subjects were eating a Standard American Diet.

Whether they’d have gotten different results on a LCHF keto diet remains a key question. My guess is that the reported hunger and irritability would have been sharply reduced if the subjects were on keto. But whether the reduction in RMR over time would have still occurred remains a gnawing question.

Here’s a pdf of the study with some relevant highlighted passages:
AlternateDayFasting.pdf (251.2 KB)

Your thoughts?

#2

Interesting read–though they do say in their conclusions that “RMR was not significantly changed after 3 wk of alternate-day fasting.” I don’t think they considered a difference of about 50 calories significant, especially since that’s about the same as the variation in measurement that they saw among the participants.

I’m not really sure what the point would be of otherwise healthy, normal weight people fasting over a long period of time. There are some benefits for specific disease treatment over longer periods. But for healthy, normal weight people, I think that an occasional fast or regular TRE (like 16:8 maybe), is about all they need to get the health benefits of autophagy over a lifetime.

(Joey) #3

@ZuleikaD Thanks for pointing this out. I took the before/after RMR figures from their exhibit and they struck me as being a meaningful difference.

So I guess the only relevant finding is that subjects who skipped every other day of eating for 3 weeks reported being hungry and irritable? Science takes a giant step forward.

(Michael - When reality fails to meet expectations, the problem is not reality.) #4

Oh, my, Joey. I already hear the rumble of the IF/EF crowd stampeding towards this! To be safe, you should probably emphasize that the study subjects were probably and almost certainly eating SAD. And that you love Jason Fung. :heart_eyes:

(Central Florida Bob ) #5

The calculator I used online turns that 375 kj change to 90 calories. Still, in CICO world, ANY excess or deficit calories matter. If you eat 50 extra calories/day for a year, that’s 18,250, and the usually quoted (though completely unsupported by real data) 3600 calories per pound turns that into 5.07 pounds/year. (90 calories a day turns into 9.13 pounds/year) But 5.07 pounds/year is also less than half a pound a month. If you’re trying to watch the scale, that’s really hard to see. That’s the problem with CICO.

Saying it was at the limits of the repeatability of their measurements is really saying the same thing.

Saying they were hungry and irritable is telling me they’re eating SAD. If you’re well fat-adapted, ADFs aren’t a big deal. I’ve been doing ADFs for the last four months.

(Joey) #6

@CFLBob Thanks for the additional math. I agree this doesn’t seem like an earthshaking difference when translated into weight (as rough as the calcs can get).

Just curious to hear your own experience being both low-carb + alternate day fasting for 4 months… would you describe yourself as being lean to begin with? Or now?

#7

The weight loss & reduction in RMR may not be significant but this bit

struck me. I’m not sure I could eat twice as much as normal on an eating day.

If I were to fast for health reasons I’d probably do longer fasts - say 3 days - 2 or 3 times a year.

(Central Florida Bob ) #8

It’s a story (of course), so do your best Grandpa Simpson voice.

I don’t think I’ve been lean in 50 years. I had been in a long term stall, like 1 year, down about 45 pounds from my peak weight. About the same time last year (in May), I started extending my 18:6 intermittent fasts mixed with OMAD to fasting three days a week. I eat MWFSat, and fast SunTuesThurs. The way the timing works out most days, is I finish dinner by about 6PM and then don’t eat until lunch time 41 or 42 hours later. That means I’m fasting 120-126 hours/week. That would be same as doing a five day continuous fast, in terms of the number of hours.

I dropped 20 pounds by last November and weights I hadn’t seen in many years. It’s not a bad weight, and doing ADFs does require some effort, so I said I’d try maintenance. Holidays coming and all. Two months later, early '19, I find I had on put more weight than I wanted (10-ish pounds?), but found I had problems fasting all of a sudden. On my re-feeding days, I had terrible GI issues. Always within a couple of hours of re-feeding. It’s not like “explosive diarrhea” is a terrible side effect. It’s painful, and sort of sucks the joy out of the day, but it’s not medically serious. It’s just not at all fun. Doesn’t make you say, “gee, I wanna do that again!”

It took me a few months of researching, reading and experimenting to figure out how to get around it. By mid-May when I started ADFs again, I was almost back to when I’d started ADFs the previous year - maybe 215. After four months, I’m getting close to last November’s weights again, currently 195. 70 lost would be 192, and I’m aiming for 75 lost. OTOH, I’ve been losing less than a pound a week. It’s slow, exasperating weight loss, but at least I can see trends.

Yesterday I had the shock of my life. I have one of those Renpho body composition scales and it tells me I’m 24.3% bodyfat. I ran into a chart I’d seen long ago on %bodyfat ranges for men. For men over 56 (I’m 65) the ideal range is 21-26% I’m almost at the middle of the ideal range.

(Joey) #9

You make a great point. But then again, if you fast for 3 days, then you’d have to eat 3x as much food on your feast day. :wink:

(Bunny) #10

I always keep in mind autophagy means the body is eating itself (using itself for fuel; catabolism) and shedding old cells and creating new cells from stem cells?

[1] “…There are three main types of autophagy, namely macroautophagy, microautophagy and Chaperone mediated autophagy. They are mediated by the autophagy-related genes and their associated enzymes. Macroautophagy is then divided into bulk and selective autophagy. …More

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As long as the carbohydrates and fat were increased and amount of protein intake remained the same for the body type in question consistent with Virta Healths recommendations[1]?

Footnotes:

[1] To Fast or Not to Fast: What Are the Risks of Fasting? “…In brief, any regimen involving fasting beyond 24-hours has not been proven effective in sustaining weight loss long term. …”

Note: Why? Because skeletal muscle volume was not increased through anaerobic (weight training) and aerobic exercise (resistance & locomotion). And nitrogen balance from protein intake was not observed?

[2] “…Basal metabolic rate (BMR) is often used interchangeably with resting metabolic rate (RMR). While BMR is a minimum number of calories required for basic functions at rest, RMR — also called resting energy expenditure (REE) — is the number of calories that your body burns while it’s at rest. …” …More

(Joey) #11

@CFLBob Thanks for your fulsome answer above. You’ve had both trials and successes along the way.

I wonder if, in your case with some extra body fat to give up, you experience those fasting days differently than someone who’s down to little excess body fat. I’m thinking both in your body’s ability to tap into the white adipose tissue and also in terms of the hormonal signals you’re getting about hunger.

When someone doesn’t have much excess body fat left to offer up, it would seem somewhat harder to (a) provide sufficient body fat to comfortably fuel 40+ hours of fasting without feeling some hunger and (b) lose weight - the latter of which is not likely even one’s objective at that point.

Personally, I eat 1.5 meals a day - a fairly light lunch and then a full dinner within a 4-5hr window. Being highly insulin sensitive and perfectly satisfied with my current weight, my ongoing interest in all the fasting-related discussions center around the potential for heightened autophagy of the healthy kind. I don’t want to slow down my metabolism by sending my body signals that it’s entering into a starvation phase. Will continue to read research and learn as I go.

(Joey) #12

@atomicspacebunny Fascinating stuff you posted (above). I will spend some time following up on this info. Besides, I love a good set of cartoons and these look like fun :slight_smile:

(Central Florida Bob ) #13

It would seem that a leaner person might have a harder time, but, (pulling some numbers out of thin air) a 150 pound 10% BF guy still has 15 pounds of fat. If that magic 3600 calories per pound is true, that’s 54,000 calories. What’s their BMR? 1500? 24 hours isn’t a stretch.

@richard has a page that discusses this topic that says a person can only use 31.5 calories per pound of fat per day


It works out that according to that calculation, I only have 1475 calories available per day, and I know I’m burning more than that. I use close to 600 just on my bike rides on fasted days. These numbers don’t add up.

I’m wary of “one size fits all” numbers like that. Virtually every other parameter you can talk about in humans has a range, not one value that would be the same for my 4’10" wife and a 6’10, 330lb NFL lineman. I expect there’s really a range of values and the source didn’t work to find those ranges.

(Joey) #14

Yeah, I’d come across such figures in the past. I thought the larger figure (like around 3500 k/cal) seemed entirely unrealistic for a daily yield … I mean, I can’t even eat 3500 kcal daily. How could a single pound of body fat produce that much daily energy?

As for the other end of the spectrum, only 31.5 kcal/pound daily seems lighter than I would have guessed. I’ve gone 24 hours fasting many times in the past - most of which were before going keto - and assuming my body requires 2000-2500 kcal/day it would’ve been impossible to stay alive since, as you note, those numbers don’t work (I’ve never had 80 lbs of excess body fat to burn).

So a realistic figure likely falls somewhere in between. Unfortunately, that’s too wide a range to make any sense out of.

What I can certainly attest to is that fasting for 24 hrs was a lot easier on keto than it ever was on a high-carb diet. Is it possible to accomplish? Sure. Would it produce meaningful health benefits in my current condition? Hard to know. That’s the question I’m still exploring.

(Central Florida Bob ) #15

Did you listen to the Dudes podcast this week? It’s all about autophagy with Dr. Nadir Ali. Rather good one.

One of those that I want to listen to again.

(Joey) #16

Haven’t heard it yet - will certainly block off some time for it. Thanks!

(Gabor Erdosi) #17

There are two very recent studies that employed ad libitum feeding. Their results are more telling IMHO.
Gabel, Kelsey, Cynthia M. Kroeger, John F. Trepanowski, Kristin K. Hoddy, Sofia Cienfuegos, Faiza Kalam, and Krista A. Varady. 2019. “Differential Effects of Alternate‐Day Fasting Versus Daily Calorie Restriction on Insulin Resistance.” Obesity . https://doi.org/10.1002/oby.22564

Stekovic, Slaven, Sebastian J. Hofer, Norbert Tripolt, Miguel A. Aon, Philipp Royer, Lukas Pein, Julia T. Stadler, et al. 2019. “Alternate Day Fasting Improves Physiological and Molecular Markers of Aging in Healthy, Non-Obese Humans.” Cell Metabolism . https://doi.org/10.1016/j.cmet.2019.07.016

#18

It’s not just what they are on their feasting days that’s in question. The big issue is whether they were fat adapted going into it. (If they didn’t mention it, the answer to that is probably no.)
Fasting studies on folks who aren’t fat-adapted should come with a huge disclaimer. It’s a different metabolic world.

(Joey) #19

@erdoke Many thanks for sharing these links!

The first one pertains to obese, insulin-resistant individuals (not fat-adapted) which, while clearly of interest, is a bit off mark in terms of applicability to lean, insulin-sensitive folks.

At first blush, the second citation seems to be more on the mark of the original topic of this thread (non-obese adults engaging in ADF), but there’s no mention of whether the subjects were on a ketogenic diet. So I’m assuming they were not, or it likely would have been a central point of the paper’s discussion.

I’ll delve in more fully in due course but a quick read suggests that, while the researchers found certain health benefits from several months of alternate day fasting, it’s unclear whether these benefits and more may have been achieved more easily through a keto diet without alternate day fasting.

Moreover, they also noted a 4.5% body weight reduction. Frankly, my primary concern about ADF is that it might promote even more weight loss (with limited, if any, incremental health benefit beyond what keto + 18/6 hr IF already produces for lean, insulin-sensitive individuals.

To be candid, I’m not sure I want to lose more weight. Of course it’s often the case that what my mind wants and what my 60+ yr old body wants for itself do not always square :wink:

But I’m not sure it’s even healthy for me to weigh much less than I did when I graduated from high school - back when I was the “skinny” kid. Moreover, I’ve got more muscle now than I had back then, so that’s got to weigh something along with my same old bones, no?

I’m presuming that as we age there’s a certain benefit to having a little extra fat to burn in case we get seriously ill. I’ve been told that having too little body fat can become a source of greater risk to recovery from a serious illness in older folks. This is not based on any science I’ve seen personally … perhaps just family medical lore. :thinking:

Anyhow, both studies will likely be interesting to read and I appreciate you’re having pointed us toward them.

(Joey) #20

UPDATE: Okay, just listened to Nadir Ali’s interview on 2KD podcast… Fascinating stuff!

Perhaps I’m hearing what I want to hear, but it sounds like lean, insulin-sensitive folks who already eat intermittently (e.g., 18/6) likely have some decent autophagy processes taking place on a daily basis.

Much of the discussions here (and limited research thus far) about fasting and autophagy are based on (1) obese/T2D subjects who are (b) insulin-resistant and eating (c ) standard SAD menus, high in carbs. If none of those factors are involved, it sounds like you get a different answer as to where the balance falls in cost/benefit of multi-day fasting.

I also heard that - for the lean, insulin-sensitive, fat-afapted individual - some light noshing (non-carb, non-protein) during a non-feast day would have much less of an effect (if any meaningful effect at all) in terms of getting in the way of autophagy, So, for example, if such an individual were to nibble some coconut oil, or perhaps a little avocado, during an otherwise “fast” day where no other food is eaten, it might strike a good balance.

Without much body fat, a lean person doesn’t have nearly as much to fuel their body without dietary nutrition as an obese person does. Not eating anything for 24 hours or longer may not be the best path forward to gain additional health benefits.

Seems like an open question that could use some directly relevant science. The studies available (of which I’m aware) seem to run the risk of missing the context that’s so essential to answering the question about the role of autophagy in such cases, and the risks of further lowering the resting metabolic rate of lean, fat-adapted, insulin-sensitive individuals.