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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