When you eat food, the body digests the macronutrients: carbohydrates, proteins – actually many different amino acids – and fats.

1) The levels of blood glucose stay higher longer because the glucose can’t make it into the muscle cells. This toxic glucose is like sludge in the bloodstream clogging arteries, binding with proteins to form harmful AGEs (advanced glycated end-products) and causing systemic inflammation. Some of this excess glucose contributes to a rise in triglycerides, increasing risk for heart disease.

2) More sugar gets stored as fat. Since the muscle cells are getting less glycogen (because they are resistant), and since insulin inhibits the fat-burning enzyme lipase, now you can’t even burn stored fat as easily. You continue to get fatter until eventually those fat cells become resistant themselves.

3) It just gets better. Levels of insulin stay higher longer because the pancreas thinks “if a little is not working, more would be better.” Wrong. Insulin is itself very toxic at high levels, causing, among many other maladies, plaque build-up in the arteries (which is why diabetics have so much heart disease) and increasing cellular proliferation in cancers.

4) Just as insulin resistance prevents sugar from entering muscle cells, it also prevents amino acids from entering. So now you can’t build or maintain your muscles. To make matters worse, other parts of your body think there’s not enough stored sugar in the cells, so they send signals to start to cannibalizing your precious muscle tissue to make more – you guessed it – sugar! You get fatter and you lose muscle. Woo hoo!

5) Your energy level drops, which makes you hungry for more carbohydrates and less willing to exercise. You actually crave more of the poison that is killing you.

6) When your liver becomes insulin resistant, it can’t convert thyroid hormone T4 into the T3, so you get those mysterious and stubborn “thyroid problems”, which further slow your metabolism.

7) You can develop neuropathies (nerve damage) and pain in the extremities, as the damage from the excess sugar destroys nerve tissue, and you can develop retinopathy and begin to lose your eyesight. Fun.

8) Eventually, the pancreas is so darn exhausted, it can’t produce any more insulin and you wind up having to inject insulin to stay alive. Lots of it, since you are resistant. Congratulations, you have graduated to insulin-dependent Type 2 diabetes.

(Anything it can’t digest, like alcohol or fiber or toxins, either passes right on through or, if it makes it into the bloodstream, gets filtered by your liver, a beast of an organ if there ever was one.)

We measure these macronutrients in grams and calories, but your body operates in terms of fuel. If you eat more fuel than your body needs – which most people do – the body is forced to store this excess.

This ability to store excess fuel was an evolutionary imperative in a world that was in a state of constant “feast or famine” 50,000 years ago.

Humans became very efficient fuel storage specialists and were able to survive the rigors of a hostile environment and pass those very same genes down to you and me.

Bear in mind that every type of carbohydrate you eat is eventually converted to a simple form of sugar known as glucose, either directly in the gut or after a brief visit to the liver. The truth is, all the bread, pasta, cereal, potatoes, rice (stop me when you’ve had enough), fruit, dessert, candy, and sodas you eat and drink eventually wind up as glucose. While glucose is a fuel, it is actually quite toxic in excess amounts unless it is being burned inside your cells, so the body has evolved an elegant way of getting it out of the bloodstream quickly and storing it in those cells.

It does this by having the liver and the muscles store some of the excess glucose as glycogen. That’s the muscle fuel that hard anaerobic exercise requires. Specialized beta cells in your pancreas sense the abundance of glucose in the bloodstream after a meal and secrete insulin, a peptide hormone whose job it is to allow glucose (and fats and amino acids) to gain access to the interior of muscle and liver cells.

But here’s the catch: once those cells are full, as they are almost all the time with inactive people, the rest of the glucose is converted to fat. Saturated fat.

Insulin was one of the first hormones to evolve in living things.

Virtually all animals secrete insulin as a means of storing excess nutrients.

It makes perfect sense that in a world where food was often scarce or non-existent for long periods of time, our bodies would become so incredibly efficient. How ironic, though, that it’s not fat that gets stored as fat – it’s sugar. And that’s where insulin insensitivity and this whole type 2 diabetes issue get confusing for most people, including your very own government.

If we go back 10,000 or more years, we find that our ancestors had very little access to sugar – or any carbohydrates for that matter. There was some fruit here and there, a few berries, roots and shoots, but most of their carbohydrate fuel was locked inside a very fibrous matrix. In fact, some paleo-anthropologists suggest that our ancestors consumed, on average, only about 80 grams of carbohydrate a day. Compare that to the 350-600 grams a day in the typical American diet today. The rest of their diet consisted of varying degrees of fat and protein. And as fibrous (and therefore complex) as those limited carbohydrate foods were, their effect on raising insulin was minimal. In fact, there was so little carbohydrate/glucose in our ancestor’s diet that we evolved four ways of making extra glucose ourselves and only one way of getting rid of the excess we consume!

Today when we eat too many carbohydrates, the pancreas pumps out insulin exactly as the DNA blueprint tell it to (hooray pancreas!), but if the liver and muscle cells are already filled with glycogen, those cells start to become resistant to the call of insulin. The insulin “receptor sites” on the surface of those cells start to decrease in number as well as in efficiency. The term is called “down regulation.” Since the glucose can’t get into the muscle or liver cells, it remains in the bloodstream. Now the pancreas senses there’s still too much toxic glucose in the blood, so it frantically pumps out even more insulin, which causes the insulin receptors on the surface of those cells to become even more resistant, because excess insulin is also toxic! Eventually, the insulin helps the glucose finds it way into your fat cells, where it is stored as fat. Again – because it bears repeating – it’s not fat that gets stored in your fat cells – it’s sugar.

The following descriptions illustrate how carbohydrates impact the human body and the degree to which we need them, or not, in our diet. The ranges represent daily averages and are subject to variables like age, current height and weight and particularly training volume. For example, a heavy, active person can be successful at a higher number than a light, moderately active person. In particular, hard training endurance athletes will experience a greater need for carbs and can adjust their personal curve accordingly. This is a topic I address further in the book (e.g. – experimenting with adding 100g of carbs per hour of training per day), on MarksDailyApple.com and in a future “primal” book dedicated to endurance athletes. Here then is my “Primal Blueprint Carbohydrate Curve.”

300 or more grams/day Danger Zone!

Easy to reach with the “normal” American diet (cereals, pasta, rice, bread, waffles, pancakes, muffins, soft drinks, packaged snacks, sweets, desserts). High risk of excess fat storage, inflammation, increased disease markers including Metabolic Syndrome or diabetes. Sharp reduction of grains and other processed carbs is critical unless you are on the “chronic cardio” treadmill (which has its own major drawbacks).

150-300 grams/day – Steady, Insidious Weight Gain

Continued higher insulin-stimulating effect prevents efficient fat burning and contributes to widespread chronic disease conditions. This range – irresponsibly recommended by the USDA and other diet authorities – can lead to the statistical US average gain of 1.5 pounds of fat per year for forty years.

100-150 grams/dayPrimal Blueprint Maintenance Range

This range based on body weight and activity level. When combined with Primal exercises, allows for genetically optimal fat burning and muscle development. Range derived from Grok’s (ancestors’) example of enjoying abundant vegetables and fruits and avoiding grains and sugars.

50-100 grams/day – Primal Sweet Spot for Effortless Weight Loss

Minimizes insulin production and ramps up fat metabolism. By meeting average daily protein requirements (.7 – 1 gram per pound of lean bodyweight formula), eating nutritious vegetables and fruits (easy to stay in 50-100 gram range, even with generous servings), and staying satisfied with delicious high fat foods (meat, fish, eggs, nuts, seeds), you can lose one to two pounds of body fat per week and then keep it off forever by eating in the maintenance range.

0-50 grams/day – Ketosis and Accelerated Fat Burning

Acceptable for a day or two of Intermittent Fasting towards aggressive weight loss efforts, provided adequate protein, fat and supplements are consumed otherwise. May be ideal for many diabetics. Not necessarily recommended as a long-term practice for otherwise healthy people due to resultant deprivation of high nutrient value vegetables and fruits.

The Primal Blueprint Carbohydrate Curve