The Carb Report: Part 2

Part 2 of the Precision Nutrition Low Carb Diet Special Report…




Ketosis has been reported to curb appetite, enhance athletic performance, and cure nearly any and all health problems that may ail you.

Anything that sounds too good to be true, probably is.


Many advocates of the ketogenic diet argue exactly that: by eating a lot of fat and almost no carbohydrates you can enjoy enhanced health, quality of life, performance, brain function, and shredded six-pack abs.



Epilepsy is a brain phenomenon known to medicine for thousands of years. To manage it, our Neolithic ancestors would drill holes in the skull in a practice known as trepanation.

Around 400 BCE, the ancient Greek doctor Hippocrates (heard of him?) observed a man who had seizures for FIVE DAYS. On the sixth day, the patient fasted (abstained from food and drink) and the seizures stopped.

About 1400 years later in 1000 CE, the Persian physician Avicenna – who came up with the term “epilepsy”, suspected that overfeeding may be a risk factor for epilepsy.

By 1911, a pair of doctors in Paris were trying fasting as a treatment for children with epilepsy, and in the US, Bernarr McFadden was claiming that fasting for three days to three weeks could cure anything.

We now know that they may be a dietary connection between brain disorders and what we eat (or don’t eat). However, fasting isn’t fun and our bodies aren’t really too keen on starvation.

So, can we get the health benefits of fasting in another way?



In 1921, endocrinology research Rollin Woodyatt noted that the same chemical environment happened with both starvation and a very low carb, very high fat diet.

At the same time, Dr. Russell Wilder and other doctors at the Mayo Clinic wondered if a person could get the health benefits of fasting without actually fasting and they experimented with what he called the “ketogenic diet” during the early 1920s. Children with epilepsy seemed to improve overall, including improved thinking and behavior.

The ketogenic diet for treatment of childhood epilepsy has been in medical textbooks since around 1940 and has stayed there throughout the 20th century.

In 2016, aging, contact sports, and modern warfare not present us with new populations whose brains might benefit from a ketogenic diet:

  • people with neurodegenerative disorders (Parkinson’s, Alzheimer’s, multiple sclerosis)
  • people with traumatic brain injury from events such as concussions or explosions



Another group of people became curious about ketogenic diets some time in the 1980s and 90s – bodybuilders and physique athletes. They had quite different goals in mind than brain health or longevity. They wanted to be crazy, shredded lean.

The questions now became:

  • Can a ketogenic diet help me perform better?
  • Can a ketogenic diet help me live longer?
  • Can a ketogenic diet help me look amazing?

The Answer? IT DEPENDS…


To give you a better idea of just HOW high fat and low carb we’re talking, here’s a comparison:

Balanced Diet:    30% Protein     40% Carb     30% Fat
Paleo Diet:     40% Protein     20% Carb     40% Fat
Low Carb Diet:     40% Protein     10% Carb     50% Fat
Ketogenic Diet:     20% Protein     5% Carb     75% Fat

Whereas a balanced meal might include a couple chicken thighs, 1/4 avocado, 1 cup asparagus, 1/2 cup brown rice, and 1/2 an apple… a ketogenic meal might include a T-bone steak topped with melted butter, 1 entire avocado, and 1/2 cup asparagus with more pats of butter.



As you’ll notice from the ratios presented above, ketogenic diets include less protein – usually closer to 10-20% of total calorie intake.


General good nutrition suggests appropriate servings of minimally processed carbohydrates, such as whole grains, beans and legumes, fruits, and starchy vegetables.

The Paleo diet eliminates grains and beans/legumes.

A low carb diet will have fewer carbs than the previous two but still have a small amount, probably from vegetables.

Ketogenic diets aim for close to zero. Perhaps 10-25 grams a day. For perspective, that’s about 10-15 grapes or a fist-sized portion of cooked carrots.


What CAN you eat?

A SMALL amount of protein: meat, poultry, fish, eggs, seafood

A LARGE amount of high-fat foods: avocado, coconut, coconut milk, coconut oil, olive oil and other oils, nuts and nut butters, bacon, egg yolks, butter, cheese

VERY SMALL amount of non-starchy vegetables: leafy greens, broccoli, cauliflower, brussels sprouts, cabbage, asparagus, cucumber, celery, tomatoes, peppers, mushrooms, zucchini

What CAN’T you eat?

Most dairy (except high-fat foods like butter and certain cheeses), fruit, grains, beans and legumes, starchy vegetables (like potatoes and winter squash) and slightly-sweet vegetables (like beets and carrots), and most processed foods.

All Fruit Final


Our body can use two types of ketones as energy sources, acetoacetate and D-β-hydroxybutyrate, and these can be made through a complex biochemical pathway in the body.

When conditions are right (during starvation or fasting, or when carb intake is very low):

  1. Fatty acids are released from stored body fat
  2. Those fatty acids enter other cells
  3. Where they are combined with coenzyme A to form acetyl-coA chains
  4. Those chains move into the mitochondria
  5. Where they are broken down into acetyl-CoA units through a process known as β-oxidation
  6. *Insert magic here*
  7. Acetyl-CoA forms ketones: acetoacetate, β-hydroxybutyrate, and acetone
  8. Ketones released by the liver into the blood
  9. Almost any cell that needs energy can take up those ketones and use them for energy – the brain requiring a large amount

Ketogenesis may be a backup energy system to ensure that the brain has enough energy even in times of starvation.

NOTE: If you want to supplement with exogenous ketones, make sure you are taking the right stereoisomer (D-β-hydroxybutyrate rather than a random mix)

Ketosis happens when blood ketones are higher than normal and is achieved either through dietary changes (leading to lower blood glucose) or through supplementation of exogenous ketones independent of blood glucose concentrations.

However, just because our body can metabolize something, does that mean that we should?

NOTE: Ketosis is different from ketoacidosis, a potentially dangerous metabolic condition. This usually happens in diabetics and alcoholics since their normal metabolic mechanisms may not work properly. For the average healthy person, dietary ketosis or brief fasting is generally considered safe.



METHOD 1: Ketogenesis

The body can make ketone bodies naturally. Fast or starve yourself for about 72 hours and ketogenesis is bound to be happening. How quickly ketosis happens varies by age and species – humans actually go into ketosis much faster than other mammals. Babies, for example, go into ketosis within a few hours of not eating.

Ketosis is essentially a side effect of fasting. This means that many of the health effects observed with fasting may be due to ketosis itself rather than energy restriction.

Our bodies prefer to store excess energy as body fat.

When we eat normally, the brain gets enough energy from glucose that can easily pass through the blood-brain barrier. When we stop eating, we run out of stored glucose (glycogen) within a couple of days, then we need to find a different source of fuel.

METHOD 2: Ketogenic diet

Since starvation is generally frowned upon and is, obvious, not sustainable, a ketogenic diet is the next best option.

By restricting the body’s glucose supply, but still providing energy and nutrients in the form of fat (and a little protein), we can reach the same end-state as starvation: ketosis.

However, it takes time.

NOTE: Many like to measure their degree of ketosis with Ketostix which tests for ketones in the urine. This is not a reliable indicator since it just tells you that you are excreting excess ketones, not necessarily that you are in ketosis. Ketostix also only measures acetoacetate, not presence of D-β-hydroxybutyrate, and excretion can change over time even when the body is still in ketosis.

METHOD 3: Exogenous ketones

Why fast or restrict carbs to make ketones when we can just take them instead?

Supplementing with ketone bodies (usually D-β-hydroxybutyrate) can raise blood ketone levels without being in ketogenesis. However, the research is still new on this one (especially in human subjects) and we don’t yet know if long-term supplementation is safe or if it can give the same health benefits as ketosis.

Almost no studies on ketone supplementation have been done in human clinical trials. Most research has been done on rats.




So if it’s been studied for so long and clearly shows benefit in certain populations, why aren’t we all eating this way?

Well, to be honest…

  • ketosis has little or no effect for many populations
  • ketosis may only work for particular types of people, for example certain health conditions or particular needs
  • ketosis may take too long to see a measurable effect
  • a ketogenic diet is too hard to consistently follow

Probably helps metabolic diseases

Fasting is often used as an effective short-term treatment for metabolic dysfunction, such as poor glucose control (early Type 2 diabetes), chronic inflammation, or hypertension. However, this may be due to apoptosis (programmed cell death) or another mechanism rather than ketosis.

Probably helps neurodegeneration and brain injuries

Research suggests that many brain disorders are related to other metabolic disorders such as diabetes, obesity, and non-alcoholic fatty liver disease. These diseases show common features, such as oxidative stress, mitochondrial dysfunction, and inflammation. Alzheimer’s is even sometimes referred to as “Type 3 diabetes”.

The presence of ketones also seems to improve outcomes from traumatic brain injury, however most studies being done are not in human subjects. Still, based on rat studies and what we’ve seen with epilepsy, chances are good that ketones are a low-risk treatment option or preventive strategy to improve brain health.

Questionably helps longevity

Caloric restriction has been shown to improve longevity in most studied organisms. Intermittent fasting seems to have some of the same benefits… sometimes. However, we don’t know if ketosis works in the same way. It’s hard to test without a control group (your identical twin who literally does everything the same as you except they eat a balanced diet and you eat a ketogenic diet).

Interesting but probably no advantage for athletic performance in most people

Athletes need fuel to perform at their best. Can tapping in to stored body fat more efficiently require less re-fueling such as carb beverages and gels?

In ketosis, you increase fat oxidation, spare glycogen, produce less lactate, and use less oxygen (at submaximal rates, like in endurance activities). You also avoid “hitting the wall” because you avoid glycogen depletion and use ketone bodies and fat as your energy source instead.

Sounds great, and while these adaptations do occur, the problem is that you’re not going to go as fast as you would when using glucose and carbohydrates as fuel. For athletes, performance is what matters most, and to date there is very little evidence to suggest improved overall athletic performance.

No advantage losing fat

Low carb advocates thought that insulin was the key to fighting fat gain. Insulin is mainly a storage hormone – it helps get nutrients into cells. Carbs (glucose) stimulate insulin release, insulin helps stuff go into cells, stuff that goes into fat cells makes us fat, so if we don’t help stuff go in to cells then we won’t get fat. Right?

Well, if you cut down on processed sugars and starches and eat more fiber and healthy fat, then possibly you may lose some weight. However, insulin is not the only hormone in your body. Energy storage is determined largely by the brain, not insulin.

On another note, eating more fat (and protein) releases satiety hormones, like CCK, that tells us we’re full. More protein and fat = feel hungry less often = eat less = lose fat. Eating less makes us lose weight, not insulin.

Also, water follows glycogen. Lower carb intake and the body will eventually release some glycogen and water along with it = magical weight loss (but not fat loss). Ketosis is not the magic bullet either – eating less is.

For women in particular, lowering carb intake may have negative effects. Women’s body react more quickly when they sense that less energy and fewer nutrients are coming in. Many women find that their hubbies look fantastic on a low carb diet, only to find that it does not work at all for them and now they’ve have screwy periods.

No advantage for gaining muscle

Insulin is mainly a storage hormone, but it is also considered an anabolic (“building) hormone. Largely, we need insulin (along with other hormones like growth hormone and testosterone) to create a muscle-building environment in the body.



If you’re someone who just wants to be healthy and fit

Try it if you’re curious, but you can be healthy, fit, and lean without it.

If you’re an athlete

Know your body and the demands of your sport. Unless you are an endurance athlete, fat-adaptation probably won’t improve your performance. Training is stressful on the body – fasting and restricting calories or a particular nutrient is also stressful. Stress adds up and can cause a host of problems, particularly in females. Active people need more fuel and nutrients than the average Joe Schmoe.

If you have a specific health problem that a ketogenic diet may assist

Consult your doctor first, stay safe by carefully monitoring and tracking any modifications, and consider hiring a dietitian to help provide guidance as well as menu planning and lifestyle advice.

SOURCE Low Carb Diet Special Report by Krista Scott-Dixon PhD and Helen Kollias PhD.

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