Dear Mark: IGF-1 and Fasting, Ex-CrossFitter Fitness Maintenance, and Barre Training

igf-fasting in lineFor today’s edition of Dear Mark, I’m answering three questions from readers. First, what’s the deal with IGF-1, growth hormone, and intermittent fasting? Some people say fasting increases growth hormones, while others say it decreases them. Who’s right? And what’s it all mean for our health? Next, how can a former CrossFitter ensure she’s maintaining her former fitness levels? And finally, what’s my take on Barre training and other “feminine” training schools?

Let’s go:

Dear Sir,

I write in the hope that you or your team can shed light on something that is confusing me and no doubt countless others!

I have read the ‘fast diet’ book and watched the BBC Horizon documentary series where Michael Mosley travels to California to meet Professor Valter Longo – who has been studying effects of caloric restriction or fasting on mice as a way of increasing life span by reducing levels of IGF1 circulating in the blood!

Now I read both here and on other sites that fasting actually increases both growth hormone and IGF1? I am confused! How can this Professor claim fasting/caloric restriction lowers IGF1 when numerous Doctors and a few body builders are using Intermittent Fasting as a way of gaining lean muscle? The information is contradictory and I am searching for truth so as I can pack on muscle while burning visceral fat at the same time!(which an almost primal diet + IF should achieve if done right) ps I’m a 35 year old, 132lb 5′ 10″ male who is physically very strong but skinny with an annoying tiny roll of abdominal fat brought about by a lifetime of consuming too many refined sugars/carbs)

Many thanks for your time, Sure hope you can help!

Best Wishes,

Stephen Peers

You’ve got it slightly wrong. Fasting has been shown to increase human growth hormone (HGH) secretion and decrease IGF-1. The two are different. The liver makes IGF-1 out of HGH, so the two are related but not the same.

As far as your question goes, increasing growth hormone through fasting should only help your quest to lean out. One study in women found that growth hormone enhanced fat loss, while IGF-1 had no effect.

IGF-1 is better for anabolism—building bones, muscle, and other tissues—but bad for autophagy, or cellular cleanup. GH doesn’t have much  direct effect on muscle growth, but it’s great for fat loss and can restore autophagy. It’s not one or the other, mind you. At least, it doesn’t have to be like that. That’s also what makes an intermittent fasting regimen work so well: you can oscillate between periods of anabolism and autophagy. The folks who just go straight ultra low calorie for years on end might extend their life (theoretically), but they usually end up skinny (fat) with poor bone density, little lean mass, and a general lack of vigor. That’s what unendingly low levels of IGF-1 will get you.

I’m not even convinced the relationship between IGF-1 and longevity is as clear as the longevity guys claim. In both human and animal studies, there’s a U-shaped relationship between IGF-1 levels and lifespan. Animal studies show an inverse relationship between IGF-1 and diabetes, heart disease, and heart disease deaths and a positive association between IGF-1 and cancer. A recent review of the animal and human evidence found that while a couple human studies show an inverse relationship between IGF-1 and longevity, several more show a positive relationship—higher IGF-1, longer lifespan—and the majority show no clear relationship at all.

The safest bet is that too little IGF-1 and too much IGF-1 are bad for us.

Here’s what we know. Too little IGF-1 and you end up with brittle bones, low muscle mass, heart disease, and reduced vigor. Too much and you might get cancer. You need a balance. You need periods of high IGF-1 (to build and grow) and periods of low IGF-1 (to repair and prune). Remember, our bodies don’t make these compounds—cholesterol, IGF-1, insulin, etc—to kill us. They serve necessary roles. Maintain skepticism whenever someone vilifies a normal physiological process or substance.

Hey Mark,
Monday’s question and answer is my favorite part of your blog. Thanks for taking the time to think about my questions. Today’s is short and sweet. I am something of a reformed hardcore crossfitter. My goal is to reduce my workload but maintain my fitness. That’s the thing…. how can I tell if I am maintaining my fitness? I have worked so hard and I am really scared of going backward.


Your faithful reader,

Lauren C.

You can definitely do it. In fact, I think you’ll find maintaining your fitness on a reduced workload is easier than you’d have guessed.

That’s basically the story of my life. After I drastically cut my training time, going from running well over a hundred miles each week to almost none, I was nervous. I’d been “fit” for so long that I couldn’t imagine doing less and getting away with it. And while I can’t run under a 2:20 marathon anymore, I’m stronger, healthier, and in less pain than I was 30 years ago in my “prime.”

I had an old girlfriend who hated the gym but loved the results it gave her. To make sure she wasn’t losing anything, she’d go once a month and perform the same workout each time—a resistance training circuit plus some cardio. If she could do it as well as she had the previous month, she was happy. She’d maintained her fitness and that was good enough for her.

Do you have a prototypical workout that defines your vision of fitness? Just do that workout every month and track your performance.

Since you’re a former CrossFitter, maybe you should pick some representative WODs and do them once every month to test your fitness.

I strongly suspect you’ll maintain or even surpass your previous bests.

If body composition is a concern, take a photo every few weeks or see how that article of clothing that’s always been a little too snug feels.

Hi Mark!

I used to run 6-10 mi every day but soon got frustrated by how my body plateaued. My doctor gave me the conventional wisdom of trying some form of light weight work so that I could strengthen and “lengthen” my muscles to bring my fitness/physical appearance to the next level. As we all know…women don’t want to bulk right? That’s when I first discovered barre-all those tiny movements up and down and inch accompanied by an undeniably challenging burning sensation made me feel so confident and strong! I truly believed every word that I was toning, drank the barre koolaid, and even got certified to instruct.

But then I found MDA. I began to lift heavier things, and I started to understand how amazing it feels to be a powerful woman. To not just aspire to be thin in an emaciated/trendy way, but fit for my body. As a barre instructor who loves teaching the method because I do think it makes a lot of women feel really good about themselves, I can struggle because I feel like the method lies to women and is just generally a very inefficient way to pursue fitness. I now love crossfit but can struggle with the old/ingrained messages of how women bulk with weight lifting.

I guess part of me still looks at the more “feminine” forms of exercise like barre or more recently the megaformer/Lagree method with some desire, and even a bit of guilt for teaching barre. What do you think about these methods of exercise? Do you see any value in these wildly popular forms of exercise?


Barre training appears to employ a lot of isometric contractions.

Yeah, you’re moving, but only ever so slightly. The effect is similar to not moving. Isometrics are great. I wrote a bit about them several weeks ago, showing that they can be effective for building tendon strength and resilience.

Those plié style squats the Barre folks do, with a wide stance, short range of motion, and turned-out toes worry me, especially when performed for high reps. They “hit your butt” really well, but in my experience do weird things to your knees.

The emphasis on “lengthening” muscles and “toning” specific “trouble” spots: these are unscientific concepts. You can’t lengthen a muscle with high-rep, low-weight lifting. Nor do low-rep, heavy-weight programs condemn you to a bodybuilder’s physique. And spot reducing simply does not work.

Lagree fitness looks interesting. Very slow, controlled movements, akin to a higher-intensity pilates. There’s some isolation, some full-body stuff. All in all, I don’t see anything glaringly wrong.

There aren’t any controlled studies on this type of training, so I don’t have any citations or references. But the general rule applies: anything that gets you moving is good. That it all seems quite safe and low-impact is another positive point. Even if it’s not the biggest bang for your workout buck, you probably won’t hurt yourself. If you do some Barre training or Lagree alongside your heavier lifting and CrossFitting, you’ll be in great shape.

Don’t feel guilty, especially if you’re helping others discover the joy of movement.


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 more than three decades 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 flavorful and delicious kitchen staples crafted with premium ingredients like avocado oil. With over 70 condiments, sauces, oils, and dressings in their lineup, Primal Kitchen makes it easy to prep mouthwatering meals that fit into your lifestyle.

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