This past week there was an online post about the need to restrict protein when following a keto diet because too much protein will lead to lower levels of ketosis. Other online sites that many people think of as credible say that eating too much protein causes the body to use glucose instead of ketones, knocking a person out of ketosis  — and will refer to ‘experts’ they’ve spoken to as sources. Do we need to limit protein and carbs? Who should we believe?
This is the post from social media that I saw this week that resulted in much discussion online, but I have edited out the name of the site because I have no issue with the website, or the author of the article. I am only using it as an example of the type of information that is being widely circulated, often without references. It reads;
“Too much protein can lead to lower levels of ketosis. Make sure that you track what you eat and monitor the amount of protein you’re eating. The average person only needs about 70-90 g of protein per day.”
The article from the same web site , presumably to which the post refers says that ‘ideal protein intake’ depends on genetics, gender, current macro intake, insulin sensitivity, how long you’ve been on keto, activity levels, current body composition and body composition goals, but that there is “no need to plug all these factors into a complex algorithm to figure out how much protein you can get away with eating”. They say that “most keto dieters” can follow the general protein recommendations they outline, namely:
Sedentary — consume 0.6 – 0.8g of protein per pound of lean body mass
Regularly active — have 0.8 – 1.0g of protein per pound of lean body mass
Lift weights — eat 1.0 – 1.2g of protein per pound of lean body mass
No references are provided in the article for the above recommendations, so how do we know?
What are evidence-based protein recommendations for those following a non-therapeutic ketogenic diet* ?
*I define therapeutic ketogenic diets as one used in the treatment of a disease, such as the classic Ketogenic Diet (KD), the Modified Ketogenic Diet (MKD), the Modified Atkins Diet (MAD). You can read more about those here.
More on that below, but first a few words about how to determine if a source of information is credible.
Scholarly Sources / References
When I cite references in my articles, it is to support the evidence for what I am writing about. As much as possible, I prefer to cite academic, peer-reviewed research papers — which means that not only are they written by experts in the field, the papers are first reviewed by other experts in the field (i.e. peer-reviewed) before the findings are published in a journal.
I also refer to published standards such as the Dietary Reference Intakes, for example and will also refer to books written by experts in the field who have previous publications in peer-reviewed journals or books for which references can be found.
I cite scholarly sources because I don’t want people to take my word for it, even though I am a published researcher with academic credentials. My readers can check the references in my articles and verify that they say what I wrote.
All too frequently, people online will say they got their information from a Mayo Clinic article, Healthline or a ‘keto’ website where the person writing the article is neither a researcher with academic credentials, nor cites scholarly sources.
There is no way to verify what is claimed as there is no trail to follow.
It may the writer’s opinion, or the opinion of an ‘expert’ they talked to, but if one can’t read the academic source of the claim, then it should be assumed to be the writer’s opinion, not evidence-based science.
Recommended Protein in a Well-Designed Ketogenic Diet
As written about in the previous article, A Keto Diet is NOT About How Much Fat it Contains, Dr. Stephen Phinney, MD, PhD and Dr. Jeff Volek, RD, PhD in their 2011 book, the Art and Science of Low Carbohydrate Living recommend that carbohydrate intake be 7.5-10% of calories for men, 2.5-6.5% of calories for women, protein intake to up to 30% of calories during weight loss and 21% during weight maintenance and fat intake to 60% of calories during weight loss and 65-72% during weight maintenance .
In relation to protein intake alone, Phinney and Volek elaborate that;
“…our studies of muscle retention and function during carbohydrate restriction [27,78,87], we recommend daily protein intakes between 1.5 and 2.5 grams per day per kg of reference body weight* .”
*reference body weight is an estimate of lean body mass — and is essentially the midpoint of the ideal body weight IBW range, by gender.
That book was written in 2011, so this morning I decided to look into what their current protein recommendations are — in light of their ongoing research in the field of ketogenic diets.
The excerpt below is from an article written by Dr. Stephen Phinney, MD, PHD, Dr. Jeff Volek, RD, PhD and Brittany Volk, PhD, RD on the Virta Health page, in an article titled “How Much Protein Do You Need In Nutritional Ketosis?”
NOTE: While this is from an article, peer-reviewed academic references are provided and it is written by well-established researchers in the field. On that basis, I consider this to be a credible source of information.
“While a precise analysis of dose-response to varying protein intakes during nutritional ketosis has not been done in humans, we have performed a number of studies indicating that most healthy humans maintain lean body mass and function during a ketogenic diet providing between 1.5 and 1.75 grams of protein per kg of ‘reference body weight’ (Phinney 1983, Davis 1990). Furthermore, there are no convincing human studies showing any benefit from dietary protein above 2.0 g/kg reference weight for adults following a ketogenic diet.
Once through the first few weeks of keto-adaptation, there does not appear to be any reason to change one’s dietary protein intake either with further time of adaptation or cumulative weight loss. The exception would be if blood ketones remain low (i.e., below 0.5 mM) despite tight carbohydrate restriction, in which case reducing protein from the 2.0 to 1.5 g/kg or even to 1.2 g/kg reference weight range might be reasonable.”
How Much Protein Interferes with Ketosis?
There is a reason Phinney, Volek and Volk do not recommend protein intakes in excess of 2.0 grams protein / kg reference body weight per day for those following a ketogenic diet:
“Protein has a moderate insulin stimulating effect; and though less than the impact of a similar amount of carbohydrate consumption, high protein intakes can drive down ketone production in the liver (Marliss 1978). In fact, specific amino acids like alanine are potently anti-ketogenic. Additionally, when consumed to excess, protein can upset gastro-intestinal function and place a stress on the kidneys to remove the additional nitrogen.”
That is, protein intake above 2.0 grams protein / kg reference body weight per day is not recommended for those following a ketogenic diet as it may reduce the amount of ketones the liver produces, and it may put stress the kidneys to remove the excess protein. But 2.0 grams of protein / kg of reference body weight per day is a huge amount of protein (more on that, below).
The Recommended Dietary Allowance (RDA) for protein is 0.8 grams of protein per kg per day, which is the level that is sufficient to meet the requirements of 97 – 98 % of healthy people. This is not the optimum requirement but the minimum.
As outlined in a previous article based on a lecture by Dr. Donald Layman, PhD, Professor Emeritus, University of Illinois, the maximum of the range of safe intake is ~200 gram protein per day and is based on >2.5 grams protein per kilogram per day. According to Dr. Layman, a high protein diet doesn’t start “until well above 170 g / day“.
Just how much protein-based food does one actually have to eat to get even 100 grams of protein, let alone more? It’s a lot more than commonly thought.
How many grams of protein is in what we call ‘protein foods’? Here are some examples from a previous article.
Egg (1 large) – 6.3 grams
Sausage, pork link (14 gm / 0.5 oz each) – 2.5 grams
American cheese (28 gm / 1 oz.) – 7 grams
Cottage cheese (250 ml / 1 cup) – 28.1 grams
Salmon (170 gm / 6 oz.) – 33.6 grams
Ham (170 gm / 6 oz.) – 35.4 grams
Tuna (170 gm / 6 oz.) – 40.1 grams
Chicken, breast (170 gm / 6 oz.) – 37.8 grams
Broiled Beef steak (170 gm / 6 oz.) – 38.6 grams
Hamburger (170 gm / 6 oz.) – 48.6 grams
Turkey, dark meat (170 gm / 6 oz.) – 48.6 grams
Pork Chop (170 gm / 6 oz.) 49 grams
Beef (170 gm / 6 oz.) – 54 grams
As outlined in many previous articles, a low carbohydrate or ketogenic diet is defined by how little carbohydrate it contains, not how much fat or protein it has.
It is a myth that there is such as thing as THE keto diet. There are many types of keto diets, with the popularized very high fat ‘keto diet’ promoted widely in the media being one type.
It is also a fallacy that the average healthy person following a low carbohydrate or ketogenic diet for weight loss or health improvements needs to limit protein.
Each individual’s macro needs (energy, protein, fat and carbohydrate) are different and vary depending on a person’s age, gender, stage of life, health conditions and activity level, so choosing the appropriate level of protein, fat and carbs in a low carbohydrate or ketogenic diet needs to be based on those — and what a person is seeking to accomplish. Is it weight loss? Is it lowering blood sugar levels? Is it optimizing health? Different goals also influence how macros are established.
We should not fear carbohydrates. They are part of real, whole foods such as low carb vegetables and fruit — and even higher carbohydrate vegetables such as yam or squash can be included in reasonable quantities in a well-designed low carbohydrate or non-therapeutic ketogenic diet and when we eat them in a meal can significantly lower their impact on blood sugar and insulin levels. We limit them to achieve our weight-loss and health-goals, but we need not nor should not avoid them.
There is no need to limit protein or in most cases to even count it except when ensuring it is adequate based on individual need. Older adults, for instance need more not less protein to lower the risk of sarcopenia, which is muscle loss as we age. It is very hard to exceed the range of safe intake for protein while eating real, whole food. There are individual cases where someone may need to monitor intake such as in pre-existing chronic kidney disease, but for the average person following a well-designed low carb or ketogenic diet, this is unnecessary.
What are “the perfect macros”? They are the one’s based on your needs and your goals.
There really is no one-sized-fits-all low carb or keto diet.
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- Clarke, Craig, ruled.me, November 30, 2020, Is Too Much Protein Bad For Ketosis [THE TRUTH], https://www.ruled.me/too-much-protein-bad-for-ketosis/
- Kimberly Holland, Healthline, People are Trying a ‘Lazy Keto’ Diet. Experts Aren’t Impressed, https://www.healthline.com/health-news/what-is-lazy-keto
- Volek JS, Phinney SD, The Art and Science of Low Carbohydrate Living: An Expert Guide, Beyond Obesity, 2011
- Phinney SD, Volek JS, Volk B, How Much Protein Do You Need In Nutritional Ketosis? February 21, 2018, Virta Health, https://www.virtahealth.com/blog/how-much-protein-on-keto