Background
This post is a review of the book ‘Metabolism Made Simple: Making Sense of Nutrition to Transform Metabolic Health’ by Sam Miller. You may recognize this name because I wrote a blog a few weeks ago that was inspired by one of his guest appearances on another podcast where he discussed his concept of the ‘five M’s of metabolism’. As I mentioned in that post, Sam is the owner of Sam Miller Science & The Metabolism School and is now an accredited author for his new book. Sam has also been a keynote speaker for major fitness and nutrition companies, he is a certified nutritionist and health practitioner, and he has also influenced thousands of fitness & nutrition coaches worldwide through workshops, classes, and other unique programs. When it comes to anything health, fitness & nutrition – Sam is a voice to pay attention to and he shows it throughout this book. This book review will be somewhat of a combination between an actual book review and a book summary.
Review
Generally, when people think of metabolism, they automatically think of your body burning fat. People also often believe that your metabolism ‘is what it is’ or that the metabolism that you are born with is the metabolism that you have to live with your entire life. They think that people that are genetically gifted with a good metabolism will never have to work to stay in shape, that people that were born with a slower metabolism are permanently screwed, and that they’ll have to outwork a bad metabolism as long as they are alive. For years, I was guilty of this thinking too. Well, good news for the people that have genetically bad metabolism and bad news for those that don’t – this isn’t the case. Although it is true that genetics play a large & predetermined role in your body composition and metabolism, there are ways to rewire your metabolism if you understand the underlying role of metabolism in your body. In this book, Sam Miller forces you to take a step back from the minute details of various diets and nutritional fads and look at the body and its metabolism from a bigger picture. This zoomed-out view of nutrition and metabolism lets you see the distinct relationship between your body’s metabolism and your diets/habits.
This book is split into two main parts: The fundamentals of nutrition and metabolism, and a more in-depth approach to successful dieting practices. Although people tend to think of metabolism in the ways described previously, Sam’s description of metabolism is ‘the measure of a body’s energy use that can also be used to describe the bodily system that operates and is adjusted dynamically to maintain life’. In this first section, he brilliantly describes your body as a biochemical supercomputer that takes in input from the outside world and operates internally to optimize survival. Your body is constantly scanning its external environment and evaluating internal hormone levels. This is what Sam refers to as your body’s own system of checks and balances. It is because of this constant scanning & internal evaluation that forces you to look at the metabolism as a dynamic equation rather than a static one. Your body is both an energy network & a feedback network.
The energy network aspect of your body is driven by what most people refer to as the energy balance: Energy in – Energy out = net energy. You may also recognize this as the golden rule of weight loss and/or weight gain. The equivalent equation is calories in – calories out = net weight gain/loss. No matter what diet or training style you follow, at the end of the day, your weight fluctuation is a function of two things: calories in (consumed) & calories out (burned). The problem is that these two things are much more complex than people think, and a lot of that is attributed to the other aspect of your body: the feedback network.
One variable in the energy balance equation is energy in. Similar to how plants use sunlight to create glucose for energy, humans also need to have a fuel source to create energy. The only difference is that because humans, unfortunately, can’t utilize photosynthesis, we have to use food for fuel instead of sunlight. I understand that a lot of people ‘know’ that food is energy, but most people don’t understand the extent of this meaning. The tricky part is that not all food is used equally for energy, and some food groups tend to serve different roles in the body. This is where macronutrients come into play. The first macronutrient is protein. Each gram of protein correlates to 4 kcals worth of energy consumed. When I think of protein, I think of structure. In addition to providing 4kcal worth of energy, Sam adds that protein triggers muscle protein synthesis, provides a higher level of satiety (feeling full/content after eating), limits weight gain, and improves body composition and metabolism. The reason I say that I relate protein to the structure is that protein is crucial to building muscle, recovery, and overall body composition. The next macronutrient is fats. When I think of fats, I think of function. Although fats generally have a negative connotation, fats are essential to many important bodily functions and provide many benefits such as optimal brain and vision function & disease prevention. There are several types of fats to be aware of: saturated fats, unsaturated fats, essential fatty acids, etc. Although it is a complex subject, the majority of fat intake should be covered by unsaturated fats & essential fatty acids. The last macronutrient is most people’s favorite – carbohydrates. When I think of carbs, I think of performance. The interesting thing about carbs is that it is the only macronutrient where there is no established minimum requirement. You need enough protein to recover and build muscle, and you need enough fats for important bodily functions, but there is no required amount of carbohydrates on a daily basis. Although not necessarily required, carbohydrates are the most efficient and powerful form of energy. This goes well beyond the scope of this review, but the body uses several different energy systems for energy production, one of which is the glycolytic system. The glycolytic system uses carbs as fuel, whereas the oxidative system uses fats as the main fuel source. Although fats are enough for the body to produce energy, the glycolytic system is much quicker and much more efficient. If you intend on doing any sort of relatively explosive exercise or anything that requires bursts of power, carbohydrates are a necessity. All of these macronutrients are stored as energy in your body to be utilized throughout the day.
The other side of the energy equation is energy out. This relates to how the energy available and stored in your body is utilized throughout the day. Although most people immediately think of exercise when considering energy out, that is nowhere near the largest contribution to your total daily energy expenditure (TDEE). Your total daily energy expenditure, or the total amount of energy you use in a day, consists of several contributors: resting metabolic rate, exercise activity, non-exercise activity, and the thermic effect of food.
Your resting metabolic rate is essentially the energy required to stay alive throughout the day or to perform normal daily activities. These activities include baseline tasks like breathing and supplying your brain with enough energy to function. Your exercise activity is pretty straightforward. This is the amount of energy you use throughout the day for purposeful exercise – lifting weights, running, etc. Non-exercise activity (NEAT) is the energy you use throughout the day to perform non-exercise-related physical tasks such as fidgeting, walking around the office, doing chores, etc. The thermic effect of food (TEF) is probably the most abstract form of energy expenditure for most people. The TEF is really just the energy your body requires in order to chew, digest and absorb the food you eat. It literally takes energy to eat your food – nice, right? Each type of macronutrient has its own separate TEF, meaning some food is more taxing on the body to digest than others. TEF is represented as a % of the total amount of kcals the food provides. For example, fats have a TEF of 0-3%. That means if you eat 100 kcal of fat, it takes ~ 0-3 kcal of energy to digest it. For comparison, carbs have a TEF of 5-10% and protein has a TEF of 10-20%. Look, yet another reason to make sure you consume enough protein throughout the day. You are burning more calories just by eating – how fun.
As mentioned, the reason this isn’t as straightforward as it seems is due to the other aspect of the body: the feedback network. The origin of our body’s feedback network is dated back to our ancestors. Back in primitive times, before there were Kroger’s and Publix, humans weren’t sure when their next meal was going to come. Their body had one goal: and that was to survive. Even back then, the human body was smart. It knew that it needed an adequate amount of food, water, sleep, sunlight, etc to optimize hormonal functions in order to survive. In order for the body to survive, it has to prioritize where to utilize the energy it has in order to increase the chance of survival. When the body is faced with a scarcity of resources, it makes hormonal and metabolic adaptations to hedge against that threat. Any extremes noted when your body does its external scanning correspond to an appropriate internal regulation, typically hormonal. For example, when your body experiences a prolonged caloric deficit, it responds by downregulating hormonal production to conserve energy. Sex hormones are decreased because your body prioritizes the energy needed for essential bodily functions rather than the energy required for reproduction. Your thyroid hormone shuts down because that is your body’s way of slowing down your metabolism to refrain from continued energy burn. These are the reasons why you see men that live in a prolonged calorie deficit (calories burned > calories consumed) have decreased testosterone or women lose the ability to have a period or get pregnant. The body has higher priorities for your limited energy than to help you reproduce. On the other end of the spectrum, if you live in a prolonged period of a caloric surplus (Calories in > calories burned), your body also has a separate set of adaptations to respond with. These adaptations consist of insulin resistance and metabolic syndrome. In the book, Sam refers to this concept as ‘overfilling your tank, with much more dire consequences than getting fuel on the exterior paint’. If your body experiences a higher intake of calories than it can burn, it will shut down – similar to when your body is burning way more calories than it can consume. Although the metabolic adaptations for a prolonged caloric deficit lead to a decreased metabolism and hormonal function, the metabolic adaptations for prolonged caloric surplus lead to several different diseases including but not limited to cancer, ovarian disease, and type II diabetes.
Dieting in general, whether for weight loss or weight gain, is the balance between satisfying the energy balance equation in your favor while accounting for your bodies hormonal adaptations. When you understand the adaptations your body is making and why it is making them, it is easier to avoid and/or push through the negative adaptations while inducing the positive ones. For example, as I mentioned a prolonged period of caloric deficit (weight loss) is typically accompanied by the body slowing your metabolism down through your thyroid hormone and shutting down your sex hormones because it has higher priorities. That is what most people refer to as weight loss plateaus. One way around this is to schedule periodic ‘diet breaks’ where you get out of the caloric deficit and raise your caloric intake for a brief period to let your body know that it does not have to go into survival mode. Once your body establishes a new baseline at this lower body weight and your hormones return to normal, then you can resume your deficit to decrease weight further. This interaction between energy balance and metabolic adaptations is also the reason why dieting isn’t as simple as ‘calories in – calories out’ over time. Because one pound of fat weighs roughly 3500 kcals, it is assumed that a 500-calorie deficit a day leads to roughly 1 lb weight loss per week. This is true at the beginning but as you lose weight, your total daily energy expenditure decreases, your metabolic requirements change, and your body starts to develop adaptations. The same can be said for weight gain. So, although it is true that calories in – calories out give you the net weight gained/lost, the way in which calories out are measured is extremely dynamic throughout time.
The second part of the book is titled ‘How to eat’. This is where Sam goes into more detail regarding what he calls the Five M’s of metabolism, the pros and cons of various diets, and some dieting strategies. I’m not going to go into as much detail regarding this section, because a majority of it is described in my recent post, ‘The Five M’s of Metabolism’. If you are interested in learning a little more about what Sam calls the Five M’s of metabolism and some keys to successful dieting, head on over and check out that post. For a quick reference, the five M’s of metabolism mentioned in this book are ‘Managing appetite’, ‘mitigating adaptation’, ‘maximizing adherence, ‘mindfulness of micronutrients’, and ‘maximizing absorption’. The essence of these guidelines can be briefly described as keeping relative levels of fullness, avoiding negative adaptations, choosing a diet that you can stick to, looking at more than just macronutrients, and paying attention to gut health. For more details regarding the five M’s of metabolism, please refer to my blog post mentioned previously.
Throughout this book, Sam Miller takes an extremely complex and dynamic topic such as the body’s metabolism, and explains it from a macroscopic & easy to digest point of view. Although people view metabolism as a genetic trait, Sam explains why it is actually a very dynamic and constantly changing phenomenon your body uses to optimize survival. Not only does Sam break down the aspects of metabolism, but he also gives approaches and methods on how to recognize what your body is doing, evaluate it, and how to go about responding to these evaluations. On top of this, in the latter chapters, Sam goes through a few fad diets that we have all heard of, explains their premise, their pros & and cons, their best use cases & more. If you are someone who wants to understand how your body’s metabolism works, wants to learn best practices on managing it, or even just general dieting and nutrition strategies, this book is absolutely worth a read.
