Dear Mark: Do I Need to Eat More, Testosterone Levels, HRV and Carbs

Heart Rate Variability FinalFor today’s edition of Dear Mark, I’m answering three reader questions. First, if things are going well on a relatively low-calorie intake, should you just keep on keepin’ on or should you increase food intake to “get ahead” of your needs? Next, what’s the deal with a study showing a high-carb diet is better for testosterone levels than a high-protein one? What does this mean for your Primal way of eating? And finally, can an improvement in heart rate variability after a carb refeed indicate a greater need for carbs?

Let’s go:

Hi Mark!

First of all, thank you the primal blueprint, I have never slept better, felt healthier and happier than this in as long as I can remember!

I started the Primal Blue print around 5 weeks ago, at the same time I have started to train MMA 4 days a week as well as three days of strength training a week.

What I have found incredible is that even with this new workload on my body, I am only feeling hungry around mid morning at which point I will have some eggs, bacon and vegetables, then I wont eat anything until I arrive home around 8 in the evening for a meal following a full days work along with strength and MMA training!

I started the blueprint weighing 243lbs with around 23% bodyfat, 5 weeks in I weigh 227 lbs, I am stronger, fitter and leaner even though I am not consuming my recommended calorie intake, not nearly as much protein as 0.7G per lb of lean body mass..

Should I consume more protein and fat regardless of my hunger level due to my training, or continue and see where the road takes me?

your advice is greatly appreciated 🙂

Many thanks,

Pretty cool how it works, huh?

I used to operate with the opposite mindset: how much food can I get away with eating? My old college buddies still call me Arnold (after the pig from Green Acres) because I ate so much, more than even the football players. I was a naturally skinny 19 year-old with an incinerator for a metabolism who ran long distances daily, and I prided myself on being able to eat as much food as I could without gaining an ounce. It was about eating, cause I’ve always loved eating, but it was also a type of ego-stroking. How much food could Arnold eat without gaining body fat? There was almost no limit, seemingly, and I prided myself on that.

These days, I’m convinced the key to health, longevity, and overall performance is to eat as little as you can get away with without sacrificing your health, performance, or energy. Eat as little food while getting the nutrients you need, without taking a hit to your performance or inhibiting your ability to enjoy life. Focus on nutrient density.

Eating Primal tends to celebrate those nutrient-dense, calorie-sparse foods. Meats (including organs), fish, eggs, leafy greens and other non-starchy vegetables (basically free vitamins and minerals). If a food is calorie-dense, like starch, make sure it’s also nutrient-dense. So, favor purple sweet potatoes or regular white potatoes over white rice.  It’s also why the use of high-quality fats is so important; grass-fed butter, extra virgin olive oil, avocado oil, and red palm oil contain nutrients to offset the caloric density.

Keep a close watch on your energy levels, body fat, and performance, though. 4 days of MMA and 3 of strength training is a lot of activity, so you may find yourself needing more food. It’s okay if you really need it. Don’t become wedded to your current eating regimen, because your response to it may change. This happens to a lot of people early on in Primal, because you’ve experienced the revelation of burning one’s own body fat for steady, clean energy. Once you get acclimated, you may need to increase calorie intake. Just be open to it is all I’m saying.

Dear Mark,

I’m trying to determine what, if any, effect(s) a lower carb approach has on Testosterone production as well as levels of Sex Hormone Binding Globulin. This study, which held total calories and fat calories constant, suggests that the higher carb diet was better at producing higher T and lowering SHBG:

I’d be interested to get your take. Thank you.


Interesting study.

The authors were comparing the effect of either high-carb or high-protein on testosterone, sex hormone-binding globulin, and cortisol. They found that high-carb resulted in higher testosterone, lower cortisol, and higher SHBG. Fat intake was held constant, so only carb and protein intake fluctuated.

I couldn’t get the full paper, so I don’t know how much protein we’re talking here, but if protein was high enough to be the predominant macronutrient in the diet, I’m not surprised.

Protein is a poor energy source. Unlike fat and carbohydrate, it can’t be directly burned or stored as energy and requires conversion into glucose before you can burn it. That conversion is energetically-demanding and metabolically costly, which makes protein great for losing weight and increasing caloric expenditure. And you need adequate protein for a healthy anabolic response. But as the predominant energy source? That’s a stressful diet, and stress is terrible for sex hormone production.

Since we’re not eating high-protein diets as much as high-fat diets, more relevant are the studies that compare high-fat to high-carb diets. On that note, high-fat seems to increase testosterone, while low-fat diets lower it. Saturated and monounsaturated fats seem to be more anabolic than PUFAs.

In an older study, men who customarily ate a 40% fat diet were placed on a 25% fat diet; the lower-fat diet also had a higher PUFA/SFA ratio and more fiber. Their total and free testosterone levels were measured pre- and post-intervention. After going lower-fat and higher-carb, total T dropped from 22.7 to 19.3 and free T from 0.23 to 0.2. Resuming their old diets partially restored their lagging T levels.

Another study in men compared a higher-fat (41%, PUFA/SFA ratio of 0.6) diet to a calorie-matched lower-fat (18.8%, PUFA/SFA ratio of 1.3) diet, finding that serum T was 13% higher on the higher-fat diet.

The ratio of PUFA to SFA also matters. Lower ratios (less PUFA, more SFA) are better for testosterone production.

As far as carbs go, if you’ve “earned” your carbs through heavy training, not eating them can depress testosterone production by creating a stressful metabolic environment.

Dear Mark,
I’ve been measuring my HRV every morning since January in order to better plan my training efforts. My average morning resting HRV is 89. My LF numbers are chronically higher than my HF numbers. I noticed after a heavy carb-binge day (Easter Cake!), though, that my HF numbers had gone up and above the LF numbers, as well as my HRV going to 95. I usually eat very low carb, but am wondering if these numbers are pointing toward me needing a few more in my diet. Obviously not looking to elevate to SAD numbers…But maybe above 80g?

Any advice would be greatly appreciated!


It couldn’t hurt to try.

This is precisely what I love about measuring heart rate variability: it gives you an objective glimpse at the suitability of your current trajectory. It’s a catch-all. If something isn’t “working,” your HRV will probably reflect it. If something works better, your HRV will probably go up a bit. The trick is to figure out the variable affecting your HRV. In your case, you’re got a good candidate.

Coming off a very l0w-carb intake—anything under 50 grams per day—I’d guess that 80 grams is a nice one to try.

And hey: just keep tracking your HRV until you find your sweet spot. Maybe it’s 80 grams. Maybe it’s 75. Maybe it’s 125. Maybe it’s very low carb for most of the week with a big carb refeed once or twice a week. You don’t know yet, but you will. With HRV monitoring, you don’t have to guess anymore.

That’s it for this week, folks. Thanks for reading!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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23 thoughts on “Dear Mark: Do I Need to Eat More, Testosterone Levels, HRV and Carbs”

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  1. Hey Mark, any personal records from your “Arnold days” at Jack’s Hot Dog Stand? Food for thought, Jack’s is turning 100 yrs old soon. I used to go there during my college days driving back from day skiing in Vermont. Jack’s was a great excuse to take the scenic route.

  2. Does insulin levels have an impact on SHBG? Does eating low carb raise the SHBG levels?
    After starting to eat primal my total testosterone went up like crazy, but so did my SHBG. Just wondering if there is any dietary hacks I can use to get the SHBG down some again.


  3. Ah, PUFAS. Is there nothing you don’t end up ruining in your excessive numbers?

  4. Interesting. I’ve never thought of using HRV as a correlate to carb intake. But it makes sense, since HRV is such a standard measure of fitness in general.

  5. Love that anecdote about “Arnold,” Mark! 😛 Boy have you (and many of us) come a long way!

  6. SHBG and HRV are spelled out (thank you), but what are HF and LF, please? Readers who are heavily into training and tracking the various body systems probably already know this, but those of us who aren’t would still like to know what the abbreviations stand for.

      1. Thanks, Mark. I thought about that but it didn’t seem to fit the comment.

  7. I think I’m going to start measuring my HRV again. Maybe I’ll do a little n=1 and do some testing in dietary, instead of mere training, situations.

  8. From all my reading over the years, regarding testosterone, it seems that there are three components to good testosterone production: 1. Proper diet (Primal comes to mind). 2. Intense physical activity (sprinting and heavy lifting anyone). 3. More sex, even solo sex. German researchers found that just having an erection can boost testosterone levels.

    1. Also watching your favorite team win. Unfortunately, when they lose you testosterone goes down instead.

      1. Place a bet on the other team. Your team wins, test up. Your team loses, you make a profit, test up.

  9. I can interject here in regards to testosterone as I’m going through this right now.

    The adrenal glands secrete to hormones: Cortisol and DHEA. Testosterone and Estrogen (yes men need this too) is created from DHEA. Cortisol and DHEA basically compete with each other meaning if you have high levels of cortisol, you’ll probably have low levels of DHEA. Elevated cortisol is basically your body’s response to stress of any kind. If you are a chronically stressed individual, you probably have high levels of cortisol, lower levels of DHEA, and more than likely lower levels of Testosterone.

    Testosterone is also manufactured from fats, but more precisely cholesterol. so the idea is to have a diet higher in fat. The problem is though, if your body has trouble breaking down the food (like if your stomach acid is low), you can’t get the nutrients out to manufacture testosterone. Low stomach acid and elevated cortisol seem to go hand in hand. Which is why it’s recommended to only eat when you aren’t stressed.

    You basically need to manage your stress better, sleep enough, eat a diet higher in fat, and if you’re have low stomach acid, take a small swig of apple cider vinegar before and after you eat.

    Where carbs come into the picture; higher carb diets seem to have a cortisol lowering effect on some people. This isn’t necessarily a bad thing, but it’s more efficient for your body to run on fat and to make the conversion to it. Going low carb when you’re not used to it can cause elevated cortisol in the interim.

  10. You said: keep a close watch on your energy levels, body fat, and performance, though. 4 days of MMA and 3 of strength training is a lot of activity, so you may find yourself needing more food.

    What are the best ways to know if you’re under eating?

    1. Being hungry (obviously, but not always by any means), craving certain foods even though you don’t think you are hungry, sleeping less well (insomnia), lethargy, not recovering for next work out, depression, higher levels of body fat (this seems counter-intuitive but place the body into perceived starvation – stressor that will trigger cortisol et al – and it will lower metabolism, waste muscle mass in favour of fat storage), particularly around the midriff.

      For the ladies loss of cycle/desire, for the gents loss of drive.

      Also bear in mind gut health, you need to feed the good guys, if you aren’t eating enough you pave the way for gut dysbiosis… list gets a bit endless there.

  11. Interesting about measuring the HRV with respect to carb intake. I never thought about correlations between the two. As per usual, your post has given me another topic to look into further. I find the data interesting for the test levels as well. I had read other sources suggesting that fat intake, specifically saturated fat is correlative with a higher testosterone level. It’s good to see a little more evidence pointing that way.

  12. I can attest that carb backloading (even “junky” carbs, e.g., sticky rice) improves the subjective quality of my sleep and increases significantly my resting HRV.

    But, I train hard and heavy. I lift five or six days a week (alternating high-volume upper body days with high-volume lower body days), do a long aerobic session on the weekends, squeeze in one to three HIIT sessions a week, and have a one hour personal training (boxing) session once a week. I’m also on my feet for 8-12 hours a day and walk a couple of miles every day.

    While I’m still relatively young (31) I’m trying to pack on 10 to 15lbs of muscle onto my already fairly athletic, 5’10, 170lbs, 13% bf frame, which is a far cry from the 220lbs I was three years ago before discovering paleo-primal and vegetables, or the 260lbs I weighed 8 years ago.

    1. You are not alone
      The solution is: read some Zen books and do some mindful jedi stuff

      At the end you will still not-know the acronyms

      But you will not mind 🙂

  13. The article’s full text is free in

    The diets were:
    “The first diet contained foods rich in protein, such as meat, fish, poultry, egg white, and a liquid dietary supplement (Sustacal, Mead Johnson and Company, Evansville, IN); in this diet 44% of total calories were protein, 35% were carbohydrate, and 21% were fat. The second diet contained carbohydrate-rich foods such as bread, vegetables, fruit, juices, pastry, and candy: in this diet 10% of total calories were protein, 70% were carbohydrate, and 20% were fat.”

  14. Interesting that high fat diets increase testosterone, didn’t realize this. I’m definitely trying to get more fats into my diet, also for cognitive reasons.

  15. I am willing to bet that if you took a healthy athletes HRV level pre injury and post injury that there would be a significant decrease in the numbers. With all of the inflammation that is occurring in the body it is easy to see why. Now, as an athletic trainer what I would like to see is if an HRV score can help a clinician determine how hard to push an athlete during rehabilitation and help make a safe return to play decision. Although the research may be limited, if we can get a good idea of what is going on inside the body without asking the simple question of “how do you feel today” and relying on the athlete to determine how hard we should push them, we may be able to shorten our rehab times and ultimately return the athlete at a safer and faster pace.

  16. I always thought that eating fatty foods reduced t levels! Any ideas which fats are best?

    Saturated, omega 6/3?

    Thanks, Mark