Hello and welcome. I’m Doctor Clyde. I have taught this course every year for Stanford Continuing Studies since 2008. The course used to be called “Food Facts Versus Fads” as a simplified version of the medical school course I taught at both Stanford and UCSF called “Food Facts, Fads, and Pharmacology.”  There are two things I have learned about nutrition over my years of teaching that surprised me the most. The first is that every crazy diet has at least a small grain of truth within it. This means every diet is “correct” to an extent (within some context) despite being very different (or even the opposite) of some other diet that is equally correct. The key to finding what works best for each of us as individuals therefore lies in discovering the universal truths underlying all dietary patterns simultaneously. It is the universal truths that best serve as a starting point for each of us to discover our own unique nutrition strategy. The second surprising thing I came to realize was that healthy nutrition requires more than simply eating healthy food.  Salad is healthy, but it might not be giving you enough of everything you need.  Drinking more water or having almonds as a snack might not either. Achieving goals requires providing enough of each thing your body needs to keep it working properly. A healthy diet therefore requires us to think about how the body works and what we might be missing. Like a car, it only takes one problem (such as a faulty engine part, a flat tire, or an empty tank) to create a bottleneck and therefore keep the entire system from functioning.  By fixing only what needs fixing (and nothing else), both your car and your body can hum along smoothly.  If you ignore or don’t know what is wrong with a system, you might go on indefinitely struggling in an uphill battle that goes nowhere.

I was born with elevated metabolic disease risks, later becoming obese with high blood pressure. These issues led to my quest to discover the universal truths that underlie our metabolism in a practical sense that I could take action on. I knew that a deeper understanding of how the body worked was the only way to overcome the disaster of the Calorie model that tends to promote excessively cutting out food groups, food portions, or both until the body shuts down even more than it already had been. In my twenties, in nuclear engineering on an aircraft carrier in the US Navy, my doctor suggested I find a good book on nutrition to lose weight and get healthier. That is when I first encountered what was not only different but opposite perspectives on how to eat. Rather than getting a book that lured me into one or another belief system, I re-engaged with my rational common sense to make better choices. My doctor was shocked at the results; he had never seen such a rapid improvement. Rational thinking had kept me from having to go on meds. What surprised me even more was the dramatic increase in my powerlifting strength that emerged from eating healthier. A dozen years later, I got my PhD in chemistry and started teaching common-sense nutrition at Stanford. The more I taught, I more I realized that our body is a system, just like the nuclear reactor plant on the ship that creates steam from fission to turn a propeller and launch jets. It has taken me a quarter century and teaching over 100 classes to simplify what our cells need into a nutrition model that shows how to adjust any dietary pattern by discovering its bottleneck, just like fixing a car. What has taken me a lifetime of rumination and research has circled me back to how our great-grandparents naturally lived their lives and what Hippocrates recognized over 2,000 years ago, which is that health derives from moderation in all things and that healthy food is medicine. Unfortunately, the prevalence of processed food and fad diets have created a confusing nutrition environment that derails our common sense. To recover it, we need a rational model of how to eat that takes into account the truths within the chaotic perspectives competing for our attention. That is the purpose of this course. Although healthy eating comes down to a balance of unprocessed foods evenly spaced throughout the day, for many, this simplicity is no longer sufficient to succeed without a rational model to guide them. A rational model for how to eat is necessarily based on how the body works. Since the body is complex, the model must be built on the principle of Einstein’s paraphrased quote to “keep things as simple as possible, but no simpler.” We want just enough complexity, without any extra, to efficiently and sustainably achieve our health and fitness goals.

I appreciate your joining me on this journey to discover your best health and fitness as a basis for achieving your best life experience. It is not an exaggeration to say our experience as living organisms depends on our physiological and psychological function, and that both of these depend on our nutrition.

These course notes are read by computer versions of my voice alternating with our “metabolic mascot” created and voiced by my 10-year-old daughter Maya. This mascot is cheering us on to achieve our metabolic goals, which include longevity, healthy weight loss, healthy weight gain, fitness, or any combination of these.  Maya visualizes Little Metabolic as a happy gene, meaning a snippet of DNA smiling as it holds out a heart in friendship. You will hear Little Metabolic and me alternating as we go along.

Here are a dozen terms helpful to our discussion on how the body works, read by myself and “Little Metabolic”

A.  Hello, this is Little Metabolic! DNA is our genetic code, which is a series of genes strung together in a row.

B.  A gene is a short segment of our DNA that encodes for one protein.

C.  RNA is a copy of a gene, meaning it is the genetic code for one protein. RNA is used by the protein factories in cells called ribosomes to assemble amino acids in the correct order for whatever protein they are making.

D.  Adenosine Tri-Phosphate or “ATP” is the energy molecule created in our cells using the oxygen we breathe and the food we eat. A steady supply of fats and blood sugar to our cells from healthy balanced eating accelerates protein production by accelerating the ATP fuel supply to the ribosome protein factories.

E.  The endocrine system consists of the organs that release hormones into the bloodstream.

F.  Hormones are signaling molecules that give the cells throughout our body instructions. 

G. Insulin is the hormone released when we eat, telling our cells to absorb Calories. Insulin is released in large amounts in response to either overeating or to fast-digesting carbs (even when not overeating). A large insulin release increases body fat by telling fat cells to 1) absorb and store Calories and 2) release less fat into the bloodstream for fuel because there are enough Calories in the bloodstream already. Most of the weight gain from repeatedly stimulating excess insulin occurs from your body holding onto its stored fat.

H.  Cortisol is a hormone that breaks down muscle in response to nutrient, mental, or physical stress, including the stress of exercise. Muscle loss reduces metabolism and fat burning, thereby increasing body fat.

I.     Amino acids are the building blocks of protein. When amino acid levels are low in the blood circulation, the brain stimulates cortisol release to break down muscle protein to provide amino acids to more vital organs.

J.   Carbohydrates generate energy 3 times faster than fat burning, making them essential for nerve signaling and intense muscle contraction. When blood sugar gets low, the brain stimulates cortisol release to break down muscle so amino acids can be converted into glucose by the liver to keep the brain functioning.

K.  Lipids are fats, including fatty acids and triglycerides for slow energy production, as well as cholesterol.

L.   Metabolism is the active burning of Calories to drive the molecular and cellular functions of living systems. Metabolism, therefore, underlies our subjective physiological and psychological vitality. Our metabolic rate refers to the rate we burn Calories, both carbs and fats, and contributes directly to our health and fitness.

The metabolic goals of healthy sustainable weight loss, weight gain, health span, and fitness are achieved by maintaining or building muscle mass while avoiding or reducing body fat. This is why maintaining relatively low insulin and cortisol levels at the same time is central to achieving health and fitness goals. Overeating at any one time results in a large insulin response (overflowing calories into lipid storage) whereas undereating or fasting raises cortisol (breaking down muscle as the body eats itself). Flip-flopping between large meals (eating whatever you want) and then skipping meals can create a vicious cycle of combined muscle loss and lipid accumulation that accelerate each other over time. This has led to the research findings that people who skip breakfast can end up burning more muscle than fat and increase their risk of cardiovascular mortality by 40%. Avoiding this requires eating a balance of unprocessed natural food evenly throughout the day as the body needs it. A balance of unprocessed natural food in moderation digests slow enough that muscle can absorb and use the nutrients that would have overflowed into fat if it had digested faster. This effectively nourishes our muscle by starving our fat. Processed carbs do the opposite, failing to keep either insulin or cortisol low. Because they digest fast, processed carbs result in a large insulin response that rollercoasters blood sugar down as it overflows to fat. This raises cortisol to break down muscle to bring it back up. These hormonal dynamics are why we can’t just eat whatever we want half of the time (leading to high insulin) and then not eat at all the other half (leading to high cortisol). And with that, we are ready to launch into our first class session!

Hello and welcome back. This is Doctor Clyde. I hope you enjoyed the course introduction, which defined some key words and concepts. The individual ideas in these notes are numbered to make clear when we are moving from one concept to the next in our stream of thought. These numbers correlate to the class lecture slides but are written so you don’t need any visuals at all. This enables you to listen while driving, walking, or relaxing so you can focus on your internal dialog and learning process. As discussed in the course introduction, the notes are read by myself and our mascot “Little Metabolic” voiced by my daughter Maya.

1.     There is a lot at stake for us to get our nutrition right because it plays a direct role in our physical and mental vitality. That vitality underlies our life experience from moment to moment and determines how long we are alive to experience those moments. This course uses a simple supply-and-demand or “flow” model using rational common sense based on how the body works to enable simple adjustments to fix any diet.

2.     The course has seven sessions. In this first session, we are building our flow model to establish the core principles of how to eat. In the next three sessions, we will discuss the importance of nutrient flow, first from the perspective of Calories, then of macronutrients, and (lastly) dive into the details of carbohydrate flow in terms of insulin sensitivity and exercise refueling. After that, in our last three sessions, we will discuss food quality (which applies particularly to vegetables and omega fats), hydration (meaning fluids), and finish with engineering our individual diets using foods we like to achieve our personal metabolic goals.

3.     Here is how I summarized the course on Stanford’s website: “Good nutrition sounds simple: eat a variety of wholesome foods and drink some water. But in our modern environment, we are surrounded by food options very different from those on a traditional farm. Low-calorie sweeteners, omega-3 fatty acids, fiber, and a multitude of additives vie for our attention, all claiming to be the key to improved health. Diets make the same claim, often appearing to have not only different but completely opposite perspectives from each other. Deprivation diets (such as keto and intermittent fasting) have recently gained interest, raising the question not simply of what to eat but also to what extent we might benefit from sometimes not eating at all. Ozempic and other drugs used to treat type 2 diabetes and obesity have gained popularity, but many come with muscle loss and (therefore) a loss of metabolism, challenging us to consider what minimal nutrition we need whether we are hungry or not. This course deconstructs our cellular needs to help guide us in putting together simple meals and snacks that help us achieve our personal goals related to longevity, health, fitness, and healthy weight loss and gain. Each homework assignment will challenge students to apply the concepts from class to their own personal lives, schedules, and food preferences. Nutrition for longevity, health, fitness, and healthy weight loss and gain will be contrasted throughout the course.”

4.     Science provides broad guidelines for meeting nutritional needs, but only when applied to each person’s unique situation does an effective and sustainable personalized approach emerge. In the end, each student’s diet will be highly individualized despite resting on the same core principles. While no science background is required, students should be comfortable hearing about scientific findings.

5.     Our cells don’t care what we eat. What they care about is getting the nutrients they need from the blood stream. Slow-digesting food eaten every 6 hours versus smaller meals every 3 hours creates the same result for your blood nutrient levels and for your cells. Whether your omega-3 fats come from fish or from walnuts makes no difference since your neurons convert shorter omegas to longer ones on site as needed. These are examples of the tremendous freedom we have in what and when we eat. On the other hand, eating nothing at all provides nothing to our cells, and if you don’t know what foods contain omega-3 fats, you would not know what foods to choose from to get them. With freedom comes responsibility, and in the case of nutrition, that responsibility refers to knowing what our cells need so that our freedom to choose does not ignore the reason we are eating to begin with, which is to nourish our bodies. This is no different from anything else in life. Consider how you get to work, for example. You might walk, drive, take the train, or work remotely through the internet. So, you have tremendous flexibility and freedom, but you ultimately must arrive somehow in the same way that the nutrients must arrive at your cells. If not, work is done by neither you nor the nutrients since they don’t get to where they need to go. By first knowing what our nutrient targets are, we can creatively frame those targets through the lens of who we are individually.

6.     As a first assignment, assess your nutrition journey. This includes your history, where you are now, and where you want to go (meaning your goals). After considering your experience, shift to considering the experience of your cells: how well have they received the balance of things they need evenly through the day over the years? And are you likely meeting their needs now? To address this question, check off some boxes in your mind: Are you drinking some water steadily throughout your day? Do you consistently provide a protein source for your body when you wake and then again in your later meals? Are you providing slow-digesting, unprocessed carbohydrates to your body to fuel your brain and accelerate healing? Dehydration, low protein, and low blood sugar levels stimulate cortisol release that breaks down muscle. Avoiding cortisol protects lean tissue to maintain your metabolism, so checking the boxes of drinking some water and eating both a protein and a slow carb is your first order of business. Then, beyond this, you must provide quality vegetables and omega fats to your body at least once per day. After going through this thought process, you might already have a sense of what has been most limiting for your progress towards your health and fitness goals.

In each class session, we will have an anchor slide outlining our sequential series of ideas covered in that session. We will periodically return to our anchor slide to remind ourselves what we have covered, where we are, and where we are going. It is our map and our compass to reorient ourselves in steps or parts.

7.     Anchor slide part A: We have set the stage for our discussion, and now shift to our metabolic model to make the point that nutrition rests on the foundation of quality sleep and must nourish the recovery of both exercise and everyday wear and tear, including stress. Without an understanding of this bigger picture, it is impossible to consider how to manage nutrition as a dynamic, interactive part of your life.

8.     A minimalist metabolic model must outline the key steps involved in burning Calories in the body. The first step is sleep, since sleep accelerates DNA gene expression, without which there is no reason to either breathe or eat, which are the second and third steps. In the fourth step, oxygen and nutrients are delivered to our cells by our circulation, and in the fifth step, those nutrients cross over into our cells by the action of hormones and transporters. The final steps are the production of ATP energy molecules by mitochondria (using oxygen and fuel), and the production of protein by our ribosome protein factories. The delivery and use of what is needed to keep our cells humming along smoothly can be thought of as a “metabolic flow” that facilitates Calorie use.  This metabolic river has a clear sequence of events, which informs us how sleep, cardiovascular health, lean muscle, hydration, food, movement, and stress interact with each other.

9.     The lifestyle intervention points for our metabolic flow therefore target sleep, nutrition, exercise, and stress.

10.  We can only benefit from what we can heal from. This is true for both mental and physical stress, including exercise damage. Nutrient, mental, and physical stress stimulate cortisol release that breaks down lean tissue. This increases metabolism briefly at the expense of long-term metabolic health. Stress management and exercise recovery are critical to maintain the metabolic flow that efficiently drives us to our goals.

11.  Research shows that overtraining is usually under-nutrition and therefore under-healing. Overtraining is a misnomer since it is caused by under-nutrition 84% of the time. Most overtrained athletes could work out harder if they provided the nourishment their cells needed to recover and adapt. 

12.  As soon as non-athletic regular people cannot fully recover from exercise, they burn less fat and less sugar than if they were not exercising at all. Published in Cell Metabolism in 2021, as people increase the amount of cardiovascular intervals from a half hour total in the first week to 1.5 hours total in the second week, they show a clear trend towards a higher metabolic rate with faster fat burning and faster sugar burning. But in the third week, when they bumped up their efforts to 2.5 hours total, their metabolism collapsed because they were not able to fully heal from the effort. This is called over-reaching and can become overtraining. You cannot benefit from anything you cannot heal from. And, in this case, fat and sugar burning actually went down to less than when doing nothing at all as soon as the effort exceeded the recovery capacity.

13.  Sleep, nutrition, movement (including exercise), and stress management are the four metabolic levers in our control because they respectively drive DNA gene expression, provide building blocks and fuel, increase the use of those building blocks and fuel, and reduce the cortisol breakdown that undoes the benefits of the other levers. These levers interact in powerful ways, such as undernutrition lowering exercise recovery and, therefore, sleep quality and energy levels, creating a negative downward spiral.