Increase testosterone by 2000% with a 24-hour fast!! Wait what?…

15 hours of fasting can increase testosterone by 1300% and 24-hour fasting can increase testosterone by 2000%!

That’s the claim made by Dr Mindy Pelz (the miracle doctor).

Derek from More plate more dates just made a good video on this so I thought to add more science to this discussion.

Fasting on total testosterone

Acute effects of fasting on testosterone

Study 1 – 56 hour fast

After 56 hours of fasting:

• Serum T fell from 870 to 570 ng/dl
• LH from 6.9 to 5.0 U/l
• Serum estradiol (E2) and FSH remained unaffected. This means that the estrogen to testosterone increased, which is not a good thing.

Interestingly, when men were given 9 small doses of glucose at regular intervals during a 56-hour fast to maintain blood glucose levels, they didn’t experience a fall in serum T or LH (R).

So it would seem that a drop in glucose leads to reduced LH release as well as testosterone production.

Can fasting increase testosterone?

Absolutely not! Under no conditions can low nutrient intake (e.g. fasting) increase testosterone.

Fasting decreases testosterone, which drops the longer you fast. pic.twitter.com/XUzf6e3AUf

— Hans Amato (@HansAmato) July 10, 2023

Study 2 – 48 hour fast

2 days of fasting reduced testosterone from 13.8 (398) to 10.91nmol/L (314.7ng/dl) (R).

Longer term fasting – 10 day fast

As you can see in this graph, testosterone decreased over a 10-day fast (R). It wasn’t too atrocious (roughly 150-300ng/dl). After the 10-day fast, they had the men refeed for 4 days and then re-test their testosterone.

Their testosterone, on average, increased over baseline after the 4 days of refeeding. One guy went from 800 at baseline to 1600ng/dl after the refeed. Another went from 700 at baseline to 500 after the refeed. So you can’t assume your test will skyrocket after a fast.

What about androgen sensitivity?

This study also shows that short-term fasting increased the GnRH-elicited LH response by 67% and the corresponding testosterone response by 180% (R).

So during fasting, you get a tradeoff between testosterone and signaling sensitivity. Lower T, but greater sensitivity. Then when you refeed you possibly get a testosterone production overshoot.

Will this enhance muscle growth? Possibly not, as the study by Moro et al (16 hour fast, 8 hour refeed window) found that the fasting and non-fasting group gain equal amounts of muscle (R).

Long-term effect of intermittent fasting on testosterone

Study 1

This 2020 study also utilizing the 16/8 fasting regime found that 4 weeks of IF didn’t lower testosterone (the average stayed around 580ng/dl) (R).

Study 2

In this 12-month study (published in 2021), time-restricted feeding (16h fast/8h feast) reduced testosterone from 19.55nmol/L (564ng/dl) to 14.61 (421.4ng/dl). Basically a 140ng/dl drop. The likely reason for this is that over time, the TRE group ate fewer calories, from 2760 to 2580 calories, whereas the non-fasting group ate roughly 2900 calories daily (R).

12 months of 16/8 intermittent fasting lowered testosterone by 140ng/dl! (from 564 to 421.4ng/dl) pic.twitter.com/LjeztzAEHK

— Hans Amato (@HansAmato) July 10, 2023

Fasting on free testosterone

Free testosterone goes down with am or pm fasting (R).

Fasting insulin drops with fasting, even intermittent fasting. Insulin is the strongest inhibitor of SHBG production. I’ve seen this very frequently in my clients who’ve done keto, carnivore or prolonged intermittent fasting. A lot of them end up with normal/high testosterone, but low free testosterone due to high SHBG.

Fasting on DHT

Fasting can lower DHT through 3 main mechanisms, namely:

• Lower insulin
• Lower NADPH
• Inadequate vitamins and minerals

Studies have shown that a higher-carb diet is better at increasing DHT than a lower-carb diet (R).

Make sure you eat enough carbs if you want to maximize your DHT.

Low-carb diets lower DHT by:
– lowering insulin
– lowering NADPH pic.twitter.com/TQWlspAQ5u

— Hans Amato (@HansAmato) July 10, 2023

This is likely due to the fact that glucose enhances the production of NADPH. More glucose = more NADPH = higher DHT.

However, there is likely a cap on this, else fruitarians should have the highest levels of DHT. You need protein, vitamins, minerals and fats as well to maximize DHT.

🧈Ultra low-fat diet experiment || My 10 day experience

Fasting on GH

Fasting is well known for its ability to increase growth hormone. This is a big reason why a lot of people actually do fasting/intermittent fasting.

Fasting for just 24 hours can nearly double the GH spike that you get.

This study found that there was a significant increase in the mean maximal GH peak amplitude between a normal day (5.9±1.1 ng/ml), the first fasted day (13.1±1.2 ng/ml) and the fifth fasted day (12.3±1.6 ng/ml) (R).

Another study found that 2 days of fasting, induced a 5-fold increase in the 24-hour GH production rate [78 +/- 12 vs. 371 +/- 57 micrograms/Lv (Lv, liter of distribution volume) (R).

Still not close to the supposed 1300% or 2000% increase.

Fasting on IGF-1

Since IGF-1 is the anabolic hormone that we actually want, let’s look at what happens to it during fasting.

This rat study found that IGF-1 dropped the longer the fast went on. The 1 kilobase IGF-I mRNA species exhibited a 43% decrease after 24 h of fasting, a 76% decrease after 48 h of fasting, and an 82% decrease after 72 h of fasting (R).

Long-term fasting will have the most potent effect on IGF-1, whereas the effect of intermittent fasting will likely be mild.

Will the spikes in GH and testosterone improve muscle growth?

GH by itself is not anabolic. It primarily increases to help mobilize fat from fat stores to provide the body with fuel.

IGF-1 is the anabolic one. However, fasting lowers IGF-1. As long as you’re not doing excessive fasting IGF-1 should decline too much. However, Moro et al in 2016 and again in 2021 found that 16/8 IF lowered IGF-1 (R).

Acute spikes in testosterone don’t improve muscle growth. This has been proven by studies showing that exercise that massively spikes GH and testosterone doesn’t increase muscle growth more than exercise that doesn’t.

It’s the long-term effects we’re after.

Summary

I’m not trying to say fasting doesn’t have benefits. Some people benefit a lot from it. If you like it, keep doing it.

But in terms of science, fasting (acute or chronic) doesn’t increase testosterone.

Fasting can however increase testosterone if it:

• Lowers inflammation
• Improves insulin sensitivity
• Helps you lose weight

However, fasting is definitely not the best way to increase testosterone.

Rather clean up your diet and lifestyle for the best (permanent) results.