How Intermittent Fasting Can Impact Testosterone Levels

When I began writing about my experience with intermittent fasting in 2018, I was 29 years old and experiencing severe job burnout.

Around that time, I learned that my testosterone had plummeted to the level of a 70-year-old man (290 ng/dL). Feeling like I had been robbed of my manhood, I was committed to doing everything I could to recover.

I had been doing intermittent fasting before, but I also continued doing the 16/8 intermittent fasting schedule throughout my recovery.

Despite the mixed scientific findings and my own experience, I am confident that intermittent fasting played an important role in boosting my testosterone levels. So much so, that I think my testosterone would have been even lower than it had been without it.

After really focusing on my health, which included IF, I was able to naturally raise my testosterone levels to that of a 17-year-old (1009 ng/dL).

But as far as research goes, it’s light and conflicted in this area. The latest evidence actually shows that intermittent fasting can hurt your testosterone levels.

Yet, we all fast overnight, so where’s that fine line between healthy, well-slept fasting and too-long intermittent fasting when it comes to testosterone production?

In this article, I’ll share the research and how to use intermittent fasting to boost testosterone, plus what mistakes to avoid.

Intermittent fasting and testosterone

You’ve likely come to this article because of one or a few reasons:

1. You have low testosterone and are wondering if intermittent fasting will help.
2. You are following an intermittent fasting plan, have low testosterone, and are worried that you’re going further downhill.
3. You’ve read the mixed research and are curious about how exactly intermittent fasting affects the hormone testosterone.

I’m going to cover all of these in this article.

When done right, intermittent fasting can have immense health benefits, and tracking your testosterone throughout is a good metric that reflects the improvements in other areas of health as well.

Why Listen to Me?

After all, I am an engineer not a doctor. I wanted to write this article for two reasons:

1. I know how absolutely horrible it feels to have low testosterone. The exhaustion — physically, mentally, and emotionally — is soul-sucking and it’s the worst I’ve ever felt in my life. If I can help others avoid this, I will.

2. Since I’ve lived through it, researched this topic extensively for over a decade, and discussed with dozens of other men over the years who have found my articles, I can share some unique insights. I was able to 4X my testosterone naturally (290 to 1150 ngl, to be exact) and my research-based articles on fasting on this blog have been read by millions of people.

I’ll do my best to decipher the most recent studies regarding intermittent fasting and testosterone. Unfortunately, the science behind intermittent fasting and testosterone is inconclusive. But, that’s not surprising because none of these studies are controlled.

In this article, I’ll cover the science and share my best takeaways from my intermittent fasting and testosterone experience.

The science of intermittent fasting and testosterone

For decades, intermittent fasting was linked to higher testosterone. This was a quick and easy conclusion to draw because it made sense.

Fasting increases HGH (human growth hormone) which helps retain and build muscle mass, stabilizes insulin levels to help our bodies burn fat, and decreases body weight. All of these things are known to increase testosterone indirectly.

However, recent studies show the opposite.

The “Against” Science

A 2022 review of studies focused on intermittent fasting and reproductive hormones found that IF can decrease testosterone in lean and physically active young men.

On the contrary, the same review admits that these men didn’t lose muscle mass or strength, nor lost levels of SHBG (sex hormone-binding globulin), a common marker used to test for low testosterone in younger men.

The study concludes with, “In interpreting these findings, it is important to note that very few studies have been conducted on this topic.”

Okay, more research is needed, but data is still data and that’s a pretty big data point. Let’s look at more data below that supports the opposite conclusion: that intermittent fasting can help improve testosterone levels.

The “Pro” Science

The benefits of intermittent fasting range far and wide, including weight loss, increased muscle mass, reduced inflammation, and stabilized insulin and hormone levels.

All of these, in turn, can have a positive, albeit indirect, effect on testosterone. The science is scarce when researching if these have a causal effect on testosterone, or are simply a by-product of being healthy. Still, I found them compelling and wanted to share them with you.

Let’s take a closer look, and for even more advantages, check out our full article on intermittent fasting health benefits.

Weight

A systematic review of forty studies found that intermittent fasters lost 7-11 lbs. on average over 10 weeks.

Excess weight is detrimental to testosterone levels because body fat increases estrogen production, which opposes testosterone production. Studies have shown unequivocally that an increased BMI, waist circumference, and body fat percentage means reduced total and free testosterone and sex hormone-binding globulin (SHBG).

Muscle Mass

Studies show that intermittent fasting promotes muscle gain due to the drastically increased production of human growth hormone (HGH), particularly during longer fasts of 36 hours or more. This is, of course, when enough calories are consumed alongside proper strength training.

HGH increases body mass, both bone and muscle mass. This is especially important as we age, and it increases our BMR and metabolism which in turn reduces body fat stores.

HGH is not a treatment for low testosterone as it has nothing to do with testosterone production. However, researchers point to the symbiotic relationship that HGH and testosterone have together, as they both affect bone density and lean body mass.

As we learned before, lean body mass and weight loss promote testosterone production, creating a full circle.

Inflammation

Intermittent fasting reduces the production of free radicals and creates a roadmap for more efficient repair, thus decreasing inflammation.

Studies have shown that when you have low testosterone, you’re likely to have high inflammation as well. It’s unclear what comes first, the chicken or the egg, or low testosterone and high inflammation, but their correlation is clear.

Insulin and Hormonal Regulation

Fasting is known to increase the hormone adiponectin, which helps balance insulin levels during a fast.

This is why, through fasting, your body has time to process glucose and increase insulin sensitivity. Over time, this yields lower body fat and higher testosterone.

Some research points to insulin as a regulator for testosterone and how high blood glucose levels directly lowers testosterone production. 

If blood sugar levels are always high (like they might be if you don’t fast long enough), then your pituitary gland cannot keep up production of the luteinizing hormone (LH). This is the hormone that stimulates testosterone production in the testes.

How intermittent fasting can increase testosterone (Best tips)

Overall, there is strong scientific indicators that intermittent fasting can positively influence testosterone levels.

Next, let’s talk strategies and best tips to make sure that you’re intermittent fasting in a healthy way that promotes — and not decreases — testosterone production.

1. Sleep is king

When does your body produce testosterone? While you sleep.

Being sleep deprived and trying to increase your testosterone levels is like trying to learn how to read by watching movies.

I don’t care how great your diet and exercise routine is. If you don’t sleep enough, forget about increasing your testosterone. I almost single-handedly attribute my burnout and low testosterone to chronic sleep deprivation.

To remedy this, I ended up quitting my job, supplementing with calcium and magnesium as prescribed by my doctor, and gave myself permission to sleep as long as I needed. For the first few months, I slept 15 hours a day. Slowly, that number came down to where it is now (8 hours) and my testosterone fully recovered to that of a 17-year-old at the age of 34.

We’re so passionate about the topic of sleep that we wrote a full article on it titled, ‘Intermittent Fasting and Sleep.’

2. Don’t fast for too long

A 16/8 fasting plan is the most common and what we follow most days. But everybody is unique and our metabolism isn’t constant (as shown in our stages of fasting experiment).

A 16/8 plan might be perfect for you while a 20/4 plan is ideal for your partner. And while a 16/8 plan is right for you in January, come July, when you’re training for a marathon, your body might need a 12/10 plan.

But the problem is it’s really hard to listen to your body and know exactly what it needs. This was the mistake I made.

Until I started using a Lumen metabolism tracker, I was fasting for too long. The tracker measures CO2 levels in your breath and gives your real-time data on whether your body is burning carbs or fat.

If you fast too long, a stress response occurs which kicks your body out of fat-burning mode. Stress is not good for testosterone production.

To really maximize your results with intermittent fasting, we highly recommend you use the Lumen metabolism tracker. This also monitors your metabolic flexibility, which is another great metric to judge your overall health. 

We tested the Lumen for 3 months and if your goal is weight loss, higher energy levels, better fitness performance, and sustainable eating habits, it’s jour #1 recommendation.

3. Don’t eat too few calories

A healthy diet does not deprive you of calories. In fact, calorie deprivation can cause weight gain.

The goal of intermittent fasting is not to eat less food, it’s to give your body time to focus on important tasks other than just digesting food and converting it to energy.

As a rule of thumb, women should consume at least 1,200 calories a day, and men 1,600. We also recommend never eating less than your basal metabolic rate (BMR). Doing so is detrimental to your health, weight loss results, and testosterone production.

4. Track your progress every 3 months

As engineers, we always say, “What gets tracked, gets improved.”

You can’t effectively increase your testosterone without knowing if your plan is working.

While I used to get my testosterone tested in a clinic for $150 each time years ago, now it’s easier and most cost-effective to take an at-home test.

That gives you flexibility which is important for consistent results. Testosterone can fluctuate considerably based on your behavior. If you get a bad night’s sleep or drink alcohol, you’ll have much lower testosterone in the morning.

For consistency, always measure after a good night’s sleep without alcoholic beverages the night before.

Alex and I were traveling during a lot of my testosterone recovery, but I was able to see my numbers jump from 290 ng/DL to 1,009 ng/DL over the course of three years, while I recovered naturally.

5. Don’t stop at intermittent fasting

Intermittent fasting is a great tool to help improve your health and testosterone levels. But it’s just one tool in a complete toolbox.

To maximize your results, you’ll need to focus on other areas as well, such as stress reduction, quality sleep, exercise, and nutrition.

Find what best fits your lifestyle and focus on what you enjoy most. This will make a healthy lifestyle more sustainable.

When I started researching low testosterone, I thought I had to eat a pound of chicken and eight egg whites per day while lifting heavy iron to succeed. I tried it and felt awful.

When my testosterone reached the highest point, I was following a vegetarian diet and training for a marathon. That’s just me, and every body is different. Do what feels good for you, and keep a journal as you try out different things.

6. Avoid TRT at all costs

Testosterone replacement therapy, unless you need it for health reasons, is a scary solution.

What struck me most about TRT was that it’s a massive business. It’s not about healthcare, it’s about insane profits.

I saw several doctors at testosterone centers and they told me to have a couple of beers and watch a late-night movie before my test so that my numbers would be low enough to be covered by insurance.

What’s most scary is that we don’t know the long-term effects, but we do know that, according to Harvard, long-term use diminishes natural testosterone production. So unless you want to get shots indefinitely, I recommend avoiding them in the first place if you don’t need them a specific medical reason.

Closing Thoughts on Intermittent Fasting Plateau

Given my experience, I could see that if you undereat while fasting. Again, IF isn’t about calorie restriction but simply eating all of your food within a certain window.

If you don’t undereat and work towards a healthy lifestyle comprising of exercise, great nutrition, and self-care, there are many indicators that intermittent fasting can promote healthy testosterone levels. This is done by enhancing body composition, regulating hormones, increasing insulin sensitivity, and maintaining or growing muscle mass.

As I mentioned before, it’s ironic that sleep is one of the single best things you can do for your testosterone, which is a fast in and of itself, yet there is some question if intermittent fasting can negatively affect testosterone.

From the studies I’ve read, I think that a relaxed schedule such as the 16/8 IF schedule wouldn’t fight against testosterone. And if you want to really be sure, it can be tracked with devices like the Lumen and, of course, with testosterone tests.

No matter which route you decide to take with your health, we like testing for a baseline and keeping a health journal before making big health changes.

Let us know your thoughts, research, and experience on the topic in the comments below. This is my story, feel free to share yours!

Feel free to download the Fasting Bundle below to help you plan, track, and succeed with both intermittent and prolonged fasting.

For more resources and guides about fasting, such as our guide to intermittent fasting and sleep, head over to our Fasting Page.