Biochemistry Primer

freeimage-4575727When I tried to explain nutritional ketosis to my family recently I was met with a lot of blank and confused looks.  I incorrectly assumed that my family knew as much as I did regarding regarding nutrition, biochemistry, and physiology and forgot that no one else in my family has a science background (I have a degree in physiology and work in healthcare).

To understand how nutritional ketosis works you have to understand a little bit of biochemistry.  So I wanted to type up something that my family and anyone else who doesn’t have a science background can refer to.

Here are a few basic topics that I think will help someone have a better understanding of nutritional ketosis (and any other diet).  I know this is extremely simplified and is extremely NOT comprehensive, but it’s as good a place to start as any.  I hope you find this helpful.

The BJJ Caveman’s Primer on Basic Biochemistry



  • Carbohydrates that you eat are combinations of sugar molecules
  • Glucose is the most common type of sugar molecule
  • Your body digests carbohydrates by breaking them down into their component sugar molecules
  • These are then absorbed into your blood stream.
  • This causes a spike in your blood glucose levels.
  • Insulin is a hormone released by your body when your blood sugar spikes to bring your blood sugar back into the normal range.
  • The glucose in your bloodstream is first used for any immediate energy needs and any left over is converted for storage.
  • Your body stores excess glucose as glycogen, which is basically a long chain of glucose molecules, to be used for energy later.
    • Only a small amount of glycogen is stored in your body (400-500 grams)
  • If too many carbohydrates are consumed, to the point where your glycogen stores are completely filled, your body converts these carbs into fat.


  • Fats that you eat are in the form of triglycerides, molecules consisting of three fatty acid chains and a glycerol molecule.
  • After a fatty meal, your body absorbs triglycerides into your blood stream.
  • Your body then uses these triglycerides for immediate energy or storage.
  • When used for energy, triglycerides need to be broken down into fatty acids before being metabolized directly for energy.
  • In situations when your body’s carbohydrate stores are depleted (as in fasting), fatty acids are broken down by the liver into ketones
    • Ketones can then be used for energy by the rest of your body instead of glucose.
  • When excess fats are consumed, they are stored within your fat cells.
    • There is no limit to how much fat you can store in your body.


  • Proteins that you eat are made up of combinations of amino acids.
  • Your body digests proteins by breaking them down into amino acids that are then absorbed into your blood stream.
  • These amino acids can then be used directly for energy or as building blocks to make essential proteins that your body needs to function (enzymes, replenishing broken down muscle, etc.)
  • When excess proteins are consumed, your body converts these additional amino acids into fat.



A key point to remember is that your body is very efficient in storing energy.  It has the ability to convert any excess carbohydrates, proteins, or fats that are consumed into stored body fat.


The Importance of Blood GlucoseBlood glucose

  • Your body uses glucose for energy and needs a constant source of it to stay alive.
  • Your body likes a blood glucose concentration of 70-100 mg/dl and it will do whatever it takes to keep the concentration in that range.
  • If there is too much glucose, such as after eating a bag of candy, and your blood glucose gets too high,
    • Your body will release insulin to bring the glucose concentration back down into the preferred range.
  • If there is too little glucose, like after a fast, and your blood glucose is too low:
    • Your body will break down any stored glycogen to make more glucose, bringing your blood glucose back into the normal range. 
    • If you run out of glycogen, your body will then find ways to make more glucose via a process called gluconeogenesis, by which your body converts other molecules into glucose.
      • The primary source of this is through the conversion of amino acids into glucose (either from ingested protein OR from the break down of proteins already in your body)
      • Your body can also convert lactate (a break down product of glucose metabolism) and glycerol (a break down product of fat metabolism) into glucose


  • Calories are a measure of energy
  • Carbohydrates, proteins, and fats all store energy
    • 1 gm of carbs = 4 calories
    • 1 gm of protein = 4 calories
    • 1 gm of fat = 9 calories
  • Your body requires a minimum amount of energy per day to function.  This is called the ‘basal metabolic rate.’
    • This does not include the amount of energy needed to do anything else such as digest food, stand up, sit down, brush your teeth, walk to work, etc.
    • My estimated basal metabolic rate is 1700 calories.
      • This is calculated from a mathematical formula.
      • You can calculate your own here.
  • When you do any additional activity, your body uses more energy.
    • For example, running a mile = 100 calories


  • Ketones are a breakdown product of fat that are only released in a low carbohydrate environment when there isn’t enough glucose
  • Ketones can be used as an alternative source of energy by almost all of your cells when there isn’t enough glucose around.
  • Ketones are actually a cleaner source of energy for your body than glucose.
    • When ketones are used for energy, they release less free radicals (toxins) compared to when glucose is used for energy.
      • An analogy would be: “ketones are to glucose what wind energy is to coal”
  • I wrote a summary trying to describe what ketones are in a little more detail
  • For a more complete explanation you can check this article out where they go into the details of the molecular structure and whatnot.


Now that you’ve made it this far and understand these topics, you should read my post about the Basics of Nutritional Ketosis!

The primary resource I used was Biochemistry (Lippincott’s Illustrated Reviews Series).


12 Responses to Biochemistry Primer

  1. naz says:

    very helpful ..

  2. Peter says:

    Question: If one were to just eat fat, w/o any carb or protein (like ice cream or cookies), how would get it stored into fat storage cells, as dietary fat itself does not trigger production of insulin?

    Does that imply for those w/ insulin level elevated when fat is consumed, some of the processed fat would be stored, along w/ the blood glucose?

    • BJJ Caveman says:

      Here is my understanding of how this works:

      To answer this, I think an important thing to clarify is that there is always SOME amount of insulin in your body. To maintain a steady state of energy your body is always producing some insulin (energy storing hormone) AND glucagon (energy releasing hormone), and the tug of war between these hormones is what helps us regulate our energy balance (a very simplistic explanation).

      The benefit of eating very low carb is that it doesn’t trigger a spike in the amount of insulin released into the blood. It’s these spikes that cause all the problems that come with eating a high carb diet.

      If one were to eat fat and only fat like a stick of butter (ice cream / cookies have tons of sugar and some protein) the following would happen:

      1. The fatty acids and triglycerides in your system will go up
      2. Your body will use this fat as energy for any immediate needs
      3. Since there is still some insulin floating around, any excess fat that isn’t used can still be stored in fat cells for use later on.

      Regarding what happens when fat and carbs are eaten together, I have read in some places that this is a bad combination because the insulin spike that comes with the carbs will cause more fat storage (from both the ingested carbs and fat).

      Hope this helps.

      • Peter says:

        Your tug of war imagery between insulin and glucagon to regulate our energy level really
        did it for me. And that may explain why a high intake of dietary fat in LCHF, a surplus way above and beyond one’s energy expenditure, may have a small impact in body mass increase. Since the insulin level is maintained at a relatively low level, not spiked by excessive glucose level, only a minute amount gets stored. Perhaps most of the excess is expelled or somehow recycled, as in this n=1 experimental result:

  3. […] For more information on macronutrients and basic biochemistry, you can check out my biochemistry primer. […]

  4. Gemma says:

    Thanks so much i am just trying ti get back into shape now my daughter is 2 & i have ver indulged over xmas & your website is so helpful & informative really making me understand where i have been going wrong! Thanks:-)

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