Truth About Protein on a Low Carb Diet

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Truth About Protein on a Low Carb Diet

Let’s talk a bit about low carb and ketogenic diets and how they truly work within your body. Once you have an understanding of how that process works, it’s much easier to understand exactly how much protein you need!

What is a ketogenic diet?

Known as ketogenic diets, they work by reducing the quantity of carbohydrates in your diet for a long enough period of time to retrain your body to turn to fats, rather than carbs, for fuel. This process is called ketosis.

By using fat for fuel, you are able to burn that stubborn stored fat while keeping your hard-earned muscle.

When you fast, reduce the carbs in your diet, are pregnant or exercise for a long period of time, your body will turn to ketones for energy.

It takes about 3-4 days of consuming very few carbs, 50 g or less per day, to kickstart ketosis. This is roughly the number of carbs found in 2 bananas.

How Does it Work?

Dietary carbohydrates are broken into glucose in the body, which is then used as your body’s main source of energy.

Not too long ago it was believed that if you went too long without food, your body would burn muscle, hence why you will hear of many bodybuilders who swear by eating every two hours, with some even waking up in the middle of the night to get more calories in.

But why would our bodies work that way? We evolved as hunters and gatherers, often going for long periods of time between meals. It only makes sense that our bodies would first burn fat rather than going to muscle for fuel.

When glucose is in short supply, your liver will break down fats into ketones, which are then used throughout your body for energy. Muscles and other tissues in your body use ketones rather than glucose for energy metabolism when you are not consuming many carbs.

In a healthy person, the production of ketones for energy is the body’s natural response to starvation, so this happens when dieting, overnight and during fasting.

Low-carb diets have been shown to help cardiovascular health and reduce your risk of type-2 diabetes, but what may be most fascinating about low-carb diets is the way that they impact your brain.

Ketosis and Brain Function

The benefits of ketogenic diets on the brain is not new knowledge. Many brain diseases, such as epilepsy, are already being treated by the ketogenic diet. The mechanisms by which it helps the brain are not yet fully understood, but there are many possible reasons as to why ketones seem to be a good energy source for the brain.

The liver produces glucose and ketones and delivers them throughout the body for energy. One of the largest organs in your body is the brain, with neurons in the brain only able to produce energy with glucose or ketones.

When your body is in a calorie deficit it can produce energy from glycogen, protein and fatty acids. Glycogen is a form of glucose stored in the body that converts fully to glucose, however your body has a very limited stored supply of glycogen.

Proteins are broken down into their building blocks, amino acids. Some amino acids will create glucose while others will create ketones, but the majority will form glucose.

Fatty-acids can also break down to form either ketones or glucose, but the majority here form ketones rather than glucose.

When you are fasting your body turns to body tissues at the rate of 26% protein and 74% fat, thus fasting is highly ketogenic, producing more ketones than glucose.

To kick your body into ketosis then you will want to strictly limit glucose intake, reduce protein intake and increase fat intake. You can intentionally consume amino acids that form ketones rather than glucose, such as leucine and lysine.

Consuming lots of short-chain fatty acids, such as those found in coconut oil, also contribute to the liver’s production of ketones.

To make a diet ketogenic, consume abundant fats, very few carbs and not excessive protein. You can then supplement with leucine, lysine and short-chain fatty acids such as coconut oil.

So How Much Protein Do I Need?

(If you want to learn more about your body, you can always apply for a consult with myself or one of my staff by CLICKING HERE )

So how much protein do you need to provide your brain with enough energy when on a ketogenic diet? This will actually change from the beginning of the diet to when you are a few weeks into it.

When consuming a traditional diet, your brain typically needs 100 grams of glucose per day.

When you are consuming a ketogenic diet, roughly 75 grams of glucose need to be produced, with the remaining coming from converting glycerol to glucose.

After your body has been running off of ketosis for about 3 weeks, the brain’s glucose needs drop to about 40 grams of glucose, over a 50% decrease in the amount of glucose needed. About 18 grams come from the conversion of glycerol with the remaining 25 grams coming from protein. This is because your brain is using more ketones rather than glucose for energy.

Because roughly 58% of dietary protein appears in the blood as glucose, we can determine the amount of dietary protein that is required by looking at dietary protein intakes and the amount of glucose that is produced.

Protein Intake (grams)Glucose Produced (grams)

Assuming the 58% conversion rate and zero carbohydrates consumed, you would need roughly 125 grams of protein per day at the start of a ketogenic diet.

After three weeks, your protein requirement would drop to only 50 grams of protein per day.

When determining how much protein you need you want to consider not only your brain’s needs but the remainder of your body as well.

There is not an exact formula that gives an individual the correct amount of protein for them – this is why you will find such greatly varying advice out on the internet regarding protein needs. The amount of protein that an individual needs varies based on factors such as age, sex, physical activity and protein source.

Nitrogen balance can be used to determine the quantity of protein needed in a diet. This is because between fats, carbohydrates and protein, only protein contains nitrogen.

If you consume excess protein, you will excrete extra nitrogen through your urine, so testing can be done to determine your protein needs.

Your protein intake is not quite as simple as grams of protein – the quality of protein consumed must also be taken into consideration.

As protein is made up of amino acids, you will need a full array of amino acids for your body to function properly. Complete proteins such as eggs, fish and meat are higher quality than foods that do not contain a complete amino acid profile.

Contrary to popular belief, there are findings that show that athletes may actually need less protein than those who are just trying to lose weight. Studies have found that exercise can make it so that your body retains amino acids rather than secreting them, making it possible that athletes may actually need less rather than more protein as your muscle protein synthesis increases while breakdown decreases.

Using nitrogen balance data it was found that the protein requirements for strength athletes is 0.6 grams of protein per pound per day and 0.5 grams of protein per pound per day for endurance athletes. This is much lower than the often touted 1 gram per pound of body weight formula.

Taking both nitrogen testing and brain energy needs into consideration, the beginning of a ketogenic diet needs to be high in protein for brain consumption. After this protein intake can then fall to as low as 50 grams of protein per day if you are smaller and up to about 0.6 grams/lb of body fat.

Because dietary protein in the body is converted to greater quantities of glucose than ketones, you do not want to consume excess protein after a few weeks into the diet or your body will have more glucose than you are intending, thus not allowing your body to produce energy through ketosis.

If you have diabetes be cautious with low-carb diets. Those with diabetes can get too high of a level of ketones in their blood, which is very dangerous. This occurs due to the low levels of insulin in the blood, which will signal the body to produce excess ketones that will build up in the blood, making the blood pH too low.



1. What is Ketosis?
2. Diabetes Education Online
3. The fat-fueled brain: unnatural or advantageous?
4. A cDNA microarray analysis of gene expression profiles in rat hippocampus following a ketogenic diet
5. Composition of Weight Loss During Short Term Weight Reduction
6. Ketogenic diets 1: ways to make a diet ketogenic
7. Our “Nitrogen Balance” article

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