When to stop fasting (if ever)?

(Oded Shopen) #1

So, I listened to the episode “ideal body weight” where they discuss the relative advantage of a little body fat. Also, there were discussions on previous episodes related to fasting, with Dr. Fung talking about fasting and weight.

I’m currently 86 kg. About 10 kg from my target weight.

At what point does fasting lose its benefits? Is there a weight goal where fasting is actually not recommended? Should extended fasting be limited at my current weight to specific range?

(G. Andrew Duthie) #2

At some point it will become difficult, if not impossible to fast without supplementing fat:

Where that line is will likely vary from person to person. I find it difficult at this point to fast without supplementing fat, which makes sense, because, assuming @richard’s calculator is accurate within reason, I can only draw somewhere between 1,000-1300 kCal/day from my own body fat. So if I don’t supplement fat at all, there’s a strong likelihood that I will force my body to lower my metabolic rate (and feel tired, cold, etc. in the process).

All that said with the caveat that while the calculator certainly seems to support my experience, it’s not a substitute for a controlled trial on multiple individuals. See what works for you by trying different things and documenting your results.

(Oded Shopen) #3

Thanks. Right now I’m on hour 26 (or 31 if you don’t count that plate of celery I had for dinner), only drinking espresso, tea, chicken broth and ofcourse water.

I have a slight headache and I have to pee a lot, but I don’t feel hungry at all. I have an X-ray tomorrow and I need to avoid fatty foods before it (how do you do that on Keto? :)), so I’m just fasting all the way through, i should be around the 50 hour mark after the test.

(Oded Shopen) #4

The calculator is great.

Although I don’t know my lean body mass, I estimate it at around 135 lbs based on height and current weight.

I also have no clue as to what my metabolic rate is, but I estimated based on the 1700 per day on the chart.

According to the results, right now I have no need for any additional fat to compensate. However, just going 5 kilos less then what I am now, and I immediately require additional 35 grams of fat per day to manage the fast normally. When I reach my target weight which is 11 kilos less than when I am now, I’ll need 84 grams of additional fat while fasting!

So, I am thinking this might be my first and last extended fast, and from now on I’ll try to focus on Intermittent Fasting.

Thanks a lot for the help!

(G. Andrew Duthie) #5

You might be underestimating, depending on your height and activity level. I’m 5’-10" and 183 currently, and I’m moderately active (started lifting 3x per week, and I play ultimate frisbee for a couple hours most Saturdays). According to this site:

That would put me between 2100-2300 kCal/day expenditure. Even dialing activity back to Sedentary puts me well over 1800 kCal/day. Just for comparison. You’re only about 3kg heavier than I am, so unless our heights are very different, I’d think you’d land in a similar range, again with activity being somewhat of a variable.

But experimentation may help you understand where you land with respect to EE. If you fast with no fat supplementation and find that you’re tired and cold, that might be a sign that you need more energy than you can get from your own body fat.

(Oded Shopen) #6

Thanks, yes after my post I went on this exact calculator, I would estimate my kCal now at around 2200. My height is 5’-8". Seems like I might be in need of some fat even right now. I guess the bottom line is that my final conclusion remains the same, this is probably my first and last extended fasting :slight_smile:.