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Book Review: Body by Science

I want to tell you about one of the best books on fitness and exercise I’ve ever read. In a way, it completely revolutionized how I think about exercise. I first purchased Body by Science in 2012 after a long stint of exploring better ways to live a healthy life.

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I picked this up after working through another fantastic book, The Primal Blueprint by Mark Sisson. To be honest, I was desperate.

You see, the nuclear alert lifestyle is straight up unhealthy. Once every three days, you’ll spend 24 hours underground in a concrete bunker the size of a school bus. You breath 90% recycled air. There is no shower, only a stamped steel prison toilet/sink combo. The food is mass produced frozen junk cooked up by an Airman who may or may not actually know what they’re doing. Your job mostly consists of sitting in a chair while staring at two screens, receiving and processing messages from command authorities and making phone calls.

I reached my heaviest point ever about halfway through my four-year alert tour. Doing P90X when it became popular helped get that weight back down, but it slowly crept back on.

I needed a change.

Mark Sisson’s book was a good first step and outlined a philosophy of nutrition, exercise, and lifestyle. But wanted more.

Doug McGuff and John Little delivered on that need.

About the Authors

Dr. Doug McGuff is a practicing emergency medicine physician and gym owner. He became interested in fitness at the age of 15 when he read Arthur Jones’ Nautilus Training Bulletin No. 2. That interest in exercise and physiology is what drove him into the medical field.

John Little has a long history with fitness research and writing. It started when he was 18 and learned directly from Mike Mentzer. He went on to work with all of the well-known bodybuilders including Arnold Schwarzenegger, and Steve Reeves. He’s also an avid student of martial arts and a renowned expert on Bruce Lee.

Body by Science

As much as I would love to dig deep into every chapter of this book, there is simply too much here to do at once. Every chapter is filled with nuggets of information that practically warrant a blog post to themselves.

You can bet that I’ll be referencing this book a lot.

In all, it’s 386 pages consisting of an introduction, eleven chapters, a twelfth chapter covering just the scientific literature used to write the book, and an index. It is a very dense piece of work.

The chapters break down like this:

  • Introduction: Whom Can You Trust?
  • Defining Health, Fitness, and Exercise
  • Global Metabolic Conditioning
  • The Dose-Response Relationship of Exercise
  • The Big-Five Workout
  • The Benefits of the Big-Five Workout
  • Enhancing the Body’s Response to Exercise
  • Tweaking the Exercise Stimulus
  • The Genetic Factor
  • The Science of Fat Loss
  • The Ideal Training Programs for Athletes
  • The Ideal Training Program for Seniors
  • Notes: The Scientific Literature Supporting Body by Science

To be honest, that’s a lot of information. I’ll do my best to highlight some information from each chapter, but realize that it will be lacking context.

Let’s get to it.

Introduction: Whom Can You Trust?

This section covers a lot of ground. Firstly, it discusses why practical fitness advice for the average person is hard to find. Secondly, it cautions you about the assumptions and myths that pervade the fitness industry.

Doug and John’s reasoning for fitness advice being difficult is sound and based on statistics. You see, they discuss the statistical standard deviation that many of us learned in high school

A standard deviation can be defined as the square root of the mean divided by the degree of variation off of that mean. So, one standard deviation from the mean to the left or to the right on the average bell-shaped curve will incorporate 85 percent of a given population. If you go two standard deviations off the mean, you are then incorporating 95 percent of that population.

The problem is that focusing on top-performing professional athletes creates the wrong assumptions. This group falls seventeen statistical deviations beyond the mean. They themselves are statistical anomalies, and the things that work for them will not work for the average person.

The same works in reverse. People often go to doctors to seek fitness advice, but doctors operate in the world of disease. Since the “average” person a doctor deals with is far left of the mean on the health and fitness scale, they have trouble assessing what works for someone who is not actually ill.

Also in the introduction of Body by Science is a fantastic myth-busting of the idea that certain exercise patterns cause specific body types. For example, people who swim a lot gain “swimmer’s bodies” and become champions. In reality, the reverse is true. People who have certain physical traits to their bodies are better at certain fitness activities and naturally rise to the top of the field.

body by science quote
This is one of the underlying themes of the book: Doing more more of a thing doesn't necessarily result in more and more benefits. It is less wear and tear on the body to do something intensely one time, and allow the body to rest and recuperate. Gaining strength and fitness is a combination of factors beyond simply lifting the weight. The goal of weight lifting is to stress the organism enough to adapt, no more.

Chapter 1: Defining Health, Fitness, and Exercise

This chapter blew my mind.

The takeaway here is that you need to disconnect health and fitness in your mind. One does not necessarily reflect the other.

Doug lays out a few definitions to back this up:

Health is a physiological state in which there is an absence of disease or pathology and that maintains the necessary biologic balance between the catabolic and anabolic states.

If you aren’t familiar with the terms, catabolic means the body is breaking down tissue and anabolic means creating new tissue. Your body does this constantly, and not just with muscle.

Fitness is the bodily state of being physiologically capable of handling challenges that exist above a resting threshold of activity.

In other words, you are physically able to meet a challenge.

Doug makes the argument that you can have an absurdly high level of fitness, but that doesn’t mean you are healthy. Consider professional athletes that have to retire early because the training regimes and abuse they put their bodies through causes early breakdown and other problems.

Lastly, Doug lays out the best definition of exercise I’ve come across.

Exercise is a specific activity that stimulates a positive physiological adaptation that serves to enhance fitness without undermining health.

Doug and John are also careful to delineate between exercise and recreation. This is an important distinction for some of the arguments they make later on. Exercise is a very specific and intentional activity designed to put the body under stress, think of lifting a heavy weight to tax the muscle. Recreation is something you do because it’s fun, even if it brings some fitness benefits. Think of hiking or casual cycling.

Chapter 2: Global Metabolic Conditioning

This chapter is about developing the body to do more work.

There are two key themes here:

  • To the muscle, mechanical work is mechanical work and it doesn’t really care about how it happened. In other words, your body doesn’t care if you puttered out on a five-mile run or a 400 lb deadlift, it interprets the failure the same way and begins adaptions to fix it
  • You can gain the same benefits of long-duration cardio training through shorter extremely intense bursts of activity

Doug goes on to describe the metabolic cycle of the cell in great detail. He uses this as a canvas to explain why traditional “cardio” is unnecessary if you exercise the muscles intensely enough through proper weight training

When I first read this chapter, I used it as an “Ah Hah!” about hating cardio at tried to never do it. I even saw benefits to my military physical fitness tests by focusing 90% of my time on heavy weight training, so the science isn’t wrong. However, there are a lot of detractors to this theory.

But that’s for another post.

Even if the suggestion that you shouldn’t do cardio is wrong, the rest of the metabolic information here and how weight lifting affects it is pure gold.

Chapter 3: The Dose-Response Relationship of Exercise

This chapter is all about muscle tissue. You’ve probably heard of fast twitch and slow twitch fibers, but there’s more to it than that.

In this chapter, Doug and John subdivide muscle tissue into four separate kinds of fibers. They then go into detail about how they function and how you can correctly exhaust each type. This is the foundation for the next chapter.

The big takeaway is that building strength and muscle is less about the number of reps and more about the time under load for the muscle. We traditionally think of more reps, and more sets, mean more gains. But their argument is that it’s all about the quantity of time you were actually supporting the weight. So, in short, why not do a single set under constant tension until the muscle fails?

Chapter 4: The Big-Five Workout

This was the chapter that convinced my girlfriend, now wife, to stop running marathons and start lifting weights. Doug and John describe a workout routine that takes about 15 minutes to complete only once per week. It only focuses on big compound movements in the major planes of human motion:

  • Horizontal push/pull
  • Vertical push/pull
  • Leg Push

I didn’t believe it when I read it, but I still put it to the test and it works.

When my wife started this routine, she pushed 160 lbs on the leg press machine. A few months later, she was moving over 300 lbs. For myself, I maxed out the allowed weight on the machine, 800 lbs, and still had more to give. I had to move to a leg press sled machine, where I was eventually doing more than 1000 lbs.

It sounds like a lot, and it is, but realize the leg press machine does not equate to squatting or dead lifting that much weight. Context matters.

I don’t want to tell you the actual workout, because that would be taking away from the authors’ work, but it’s pretty darn simple to execute in theory. It is uncomfortable, though, while you learn to ride the wave of muscle exhaustion and burn.

A few years after this book came out, Tim Ferris described a similar workout in his book The Four-Hour Body.

I haven’t actually followed this workout routine in a while, but I may return to it for a bit after I finish my current cycle with dumbbells.

Chapter 5: The Benefits of the Big-Five Workout

This chapter is less about the workout and more about the benefits of having more muscle. I don’t need to tell you about things like improved ability to go out and live life. You already know that. But something else stood out to me when I read this for the first time.

The medical literature affirms the absolute role that increased muscle mass plays to one’s benefit during life-threatening situations. A lot of the beneficial effects of strength training come from the fact that the other organs of the body increase their functional capacity to track, one to one, with increases in muscle mass. As an example, if you were to be in a severe traffic accident and had to be admitted to an intensive care unit, the “start” point from which you would atrophy all of your organs is predicated on your degree of muscle mass. In other words, how long it would take before you reach multi-system organ failure and die is directly linked to your level of muscle mass, because all of your other organ weights are going to be proportional to that.

Strength training directly impacts the body’s ability to process glucose and raises insulin sensitivity. Both of these are important for diabetics, or anyone whose family has a proclivity for Type 2 Diabetes (as mine does).

Doug goes on to list and explain a litany of other benefits:

  • Improved metabolism
  • Release of body fat stores
  • Lower cholesterol levels
  • Improved blood pressure
  • Increased bone mineral density
  • Cardiovascular health

You get the idea. Strength training is one of the single most helpful activities you can do for yourself.

Chapter 6: Enhancing the Body’s Response to Exercise

This chapter is all about additional lifestyle factors that aid in your pursuit of health and fitness. The advice is probably nothing you haven’t seen before, such as adequate sleep, hydration, and nutrition but Doug and John go very deep into what happens at the cellular level.

I’ve never come across another book that goes this deep into the “why this works” explanations as this one does.

Something else I appreciate is the emphasis on managing day-to-day stress.

Chapter 7: Tweaking the Exercise Stimulus

This chapter covers adjusting the workout program to continue progress. The authors admit that things do not progress on a linear curve forever. Eventually, you’re going to run into the mechanical limitations of the equipment, as I did by maxing out the weight on the leg press machine at my old gym, or your workouts become so intense that it takes longer than a week to recover.

To combat these factors, Doug and John provide modifications to the routines. This may look like utilizing a training partner to assist at certain portions of a movement, or splitting the workouts into a two or three-week cycle.

If you’ve ever done Mark Rippetoe’s Starting Strength program, as I have, then you’ll quickly recognize how this kind of cycling works.

This chapter also covers some different isolation movements you could sprinkle into the workouts.

Something to point out here is that Doug and John almost entirely focus on the use of machines rather than free weights. They provide a lot of reasons for this, and a lot of it comes down to minimizing the variables that might lead to injury due to poor form. They also point out that some machines do a very good job of following the strength curve of a muscle contraction.

body by science
A portion of the book discussing how timing affects muscle failure

You see, a muscle is at its strongest when its somewhere in the middle of the range of motion. When it’s fully contracted for fully extended, it can’t generate the same amount of force from a standstill. Well-designed machines have cam systems that account for this, kind of like compound archery bows. Free weights, as I typically do, are the opposite end of the spectrum. That works fine when your sets are relatively short and you maintain good form, but the risk of poor form and injury goes up as you exhaust the system.

Chapter 8: The Genetic Factor

The gist of this chapter is that people need to stop focusing on genetic outliers like Arnold Schwarzenegger. Women avoid weight lifting heavy enough because they fear to look like that. Men quit weight lifting in frustration because they don’t quickly obtain those results.

The point the authors make is that professional bodybuilders like Arnold, aside from the chemical assistance, have genetic predispositions to gaining muscle in that way. They are many many standard deviations beyond the mean.

The average person lifting weight will never look like that. With that said, Doug and John emphasize that lifting weights consistently is one of the most productive activities you can engage in for your body.

The chapter goes into all of the genetic and environmental factors that go into this. It’s probably a little too “high level” for most people, but the explanations are solid.

Chapter 9: The Science of Fat Loss

This chapter is awesome.

I read this book right after working through Mark Sisson’s Primal Blueprint, and the two just mesh so well together. The chapter opens by discussing how and why the body stores fat, including the hormones involved in doing it. I appreciate that they start off by saying that fat is actually an amazingly helpful tissue in the body, and contributed to our survival for millennia.

The problem is that modern lifestyles abuse the very systems that contribute to our survival through hard times and food scarcity.

The real source of modern obesity is food abundance. If we were to give you a jumbo industrial role of toilet paper and allow you to hold it while we unwind it, you would end up with a very long strand of toilet paper. If we tore off the last square, leaving you with the rest, your length of toilet paper would represent the period of human history during which starvation was a real day-to-day threat. The single square remaining would represent the period of history during which the threat of starvation had been for the most part addressed…The problem is not that people today are inactive; the problem is that calories are so readily available to be consumed.

Doug and John make the point that increasing your activity level doesn’t actually increase your calorie burn all that much, even though the fitness industry keeps telling you that. However, they argue that increasing your muscle mass has a direct impact on your metabolism. Muscle, you see, is a metabolically expensive tissue.

That said, they also make the point that you still have to eat an appropriate diet. You can’t out-exercise poor nutrition. They particularly call out processed foods, since the body so easily digests and stores them.

If you consume 2,000 calories of refined carbohydrates, the metabolic cost of processing this intake and converting it into stored energy (body fat) is close to zero. If you instead consume lean meats, fruits, and vegetables, the metabolic cost of converting these foodstuffs into usable energy is high...A natural diet provides a double metabolic advantage in that it promotes a higher thermic cost of digestion and keeps insulin levels lower, enabling fat loss to occur in the face of a calorie deficit

There are some hormonal things here that I left out, and I’ll write about them in another article. But one of the things you should know is that your body will not use fat for fuel in the presence of insulin.

Chapter 10: The Ideal Training Programs for Athletes

This chapter offers some specific training programs for popular sports. But more importantly, it highlights the difference between general physical conditioning and sport specific training.

Rob Shaul at The Mountain Tactical Institute talked about the same thing in another post.

The thing to look at here is that physical conditioning is your baseline program. As the competitive event approaches, you stop the baseline program in favor of skill or sport-specific training.

Chapter 11: The Ideal Training Program for Seniors

I like that Doug and John open the chapter with a bold statement.

Senior citizens need to let go of the idea that somehow they’re different from the rest of the population because of their age. Being older doesn’t change much of anything on that front. All of the physiological mechanisms necessary for the human body to produce a physiological adaptation to the exercise stimulus remain intact through every stage of life. The only meaningful difference that pertains from a physiological standpoint with regard to older people versus younger people is that the older population has had more time for the deconditioning process to do its damage.

The authors do highlight that seniors need to be extra careful of correct form and range of motion, though. Recovery time is may be longer, but the need to train is not diminished. They also provide a different workout program who find the Big-Five system too taxing.

They also highlight a myriad of benefits to seniors who engage in weight training, though they don’t come as a surprise compared to everything else in the book.

Notes and Citations

The final portion here (I’m skipping over the index) is 24 pages of citations for various research journals, studies, and articles. It’s one of the most thorough I’ve come across.


When it comes to health and fitness, this is hands down one of the best books on my shelf. The information about metabolism, fat loss, and muscle physiology is amazing. The workout program they prescribe is indeed effective, even though it seems counter-intuitive.

With all of that said, don’t make the same mistake I did and go “all in” on the high-intensity training concept. There are absolutely proven benefits to doing so, but I think a lot of people have gone over the deep end with it.

For example, Doug and John come across as somewhat dismissive of traditional cardiovascular training. It’s not that they don’t think it’s helpful, but that they see it as unnecessary. If anything, the repetitive motion of most cardio training activities could cause undue wear on the joints. If their underlying goal is promoting activities that improve overall fitness without undermining health, then I understand their angle.

But on the flip side is the work of guys like Phil Maffetone, who I’ve quoted on this blog before.

Acolytes of each system, the Low-Intensity Solid State (LISS) of Maffetone and the High-Intensity Training (HIT) of McGuff are often at odds. I found that Clarence Bass had the best compromise of the two, but that’s for a different article.

Would I recommend this book? Absolutely. You’ll be combing through it and coming back to reread things for years. Just realize that there are other competing theories and books out there that also produce results.

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Matt is the primary author and owner of The Everyday Marksman. He's a former military officer turned professional tech sector trainer. He's a lifelong learner, passionate outdoorsman, and steadfast supporter of firearms culture.

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Have you experimented with kettlebells yet?

Replying to  The Marksman

I’ve read a couple of his books. I wish he had dialed down the whole “comrade” BS, but I guess that is how his marketing works. I was also familiar with them from my childhood in Russia, of course. I am naturally big and as many naturally strong people, I never saw the need for strength training. I am a life-long martial artist and speed was my problem, not strength. As a got older and bigger, I kept practicing, I started accumulating joint injuries. They were not strong enough to sustain the dynamics of the movement I needed. Weirdly, I was getting even more injuries from table tennis, of all things, because of the speed requirements. Eventually, I stopped for a bit to let everything heal and then started using kettlebels CoC grippers to re-build dynamic strength and stabilizer muscles. It was tremendously helpful and other than a recent knee injury that might be the onset of arthritis most of my joint issues have gone away.

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