This post is going to be unpopular with those who believe that ketosis requires one to strictly limit carbohydrate levels to 20 grams net carbs and less, but I think this needs to be said. I have mentioned in previous posts (here and here) that a ketogenic diet requires a person to minimize carbohydrates in order to induce ketone creation and begin to use ketones for fuel. Once in nutritional ketosis, however, it is very possible to produce ketones while eating a higher amount of carbs. And there are some very good reasons to increase carb limits above the “20 grams per day” rule under which many ketoers remain. For some people, eating higher level of carbs is not just an option—it is the preferred option over eating 20 grams and under.
How did the “20 grams carbs a day” limit originate?
Dr. Atkins (Atkins, 1992) was the first to popularize the dietary protocol that most people use to start their ketogenic journey. He suggested limiting “impact” or net carbs to 20 grams per day from vegetable sources, a phase that he called Induction, to minimize the effects of dietary carbs on glucose levels. This phase allows the body to deplete its glucose stores, a necessary step for encouraging the body to produce and utilize ketones to replace glucose. But the most essential component often escapes nutritional ketosis followers today. There are ongoing phases of his program after Induction during which people are—not just allowed, but—encouraged to eat more carbohydrates. His daily carb recommendations for his second phase, Ongoing Weight Loss, were as follows:
• eat 15 grams and less for those with high metabolic resistance;
• eat 15-40 grams for those with average metabolic resistance;
• eat 40-60 grams for those with low metabolic resistance; and
• eat 60-90 grams for a regular exerciser (defined as one who engages in vigorous exercise 4-5 days a week).
These recommendations change again for phase three, Lifetime Maintenance:
• eat 25-40 grams and less for those with high metabolic resistance;
• eat 40-60 grams for those with average metabolic resistance;
• eat 60-90 grams for those with low metabolic resistance; and
• eat 90 grams or more for a regular exerciser.
How did we get from 20 grams carbs a day during the first weeks of induction to 20 grams carbs a day for life?
The short answer is this: if a little is good, then more must be better. Dr. Atkins recommended that those with metabolic resistance, defined as those who have “a lot of weight to lose or have difficulty losing weight,” extend the induction phase indefinitely in order to “see dramatic progress before moving on to the more moderate phases of the program” (Atkins, 1992, p. 159). The lure of a ketogenic diet is foremost related to fat loss and mobilizing body fat stores. At a secondary level, reducing or eliminating carbs helps the body to reduce its fasting insulin levels and reduce high blood glucose, which is great for diabetics and people who struggle to process eating an excess of carbohydrates. Somehow, however, the promise of quick fat loss from limiting carbs to 20 grams per day was too enticing to pass up. Eating just 20 grams carbs a day was somehow applied to both sick and healthy populations like, and now it extends to a much larger population than was originally intended. Not everyone in ketosis has metabolic resistance. And if they did when they started, they have certainly undergone some measure of healing from having eliminated many problem foods and substantially reduced others.
In other words, if you are not sick or metabolically deranged, there is no reason for you to limit your carbs to 20 grams per day. Nutritional ketosis can be maintained at much higher carb levels, and there are good reasons to at least consider doing so.
Severely limiting carbs is a necessary first step for inducing ketosis, but continuing to limit carbs this strictly on an ongoing basis does not work well for everyone. It often induces problems in the long run, particularly for healthy people (those not suffering from metabolic resistance), those who exercise regularly and people who have reached their weight goals. While some seem to thrive limiting carbs to 20 grams (at least in the short term), others suffer ill consequences with the mistaken impression that forcing themselves to continually limit carbs will somehow do their bodies good. Men have more flexibility with keeping carb levels very limited, just as men seem to fair better with long term fasting and bigger caloric deficits (Ruper, 2012), but women are more likely to suffer the ill consequences of restriction faster. The body uses a process called gluneogenesis (see last week’s post) wherein protein and fat are converted to glucose to meet the body’s essential needs. The problem, however, is that gluconeogenesis often does not meet the non-essential needs that require glucose. Instead, many of those functions are shut down. When people keep their carb levels so low for long periods, they may not even realize what they are doing to their bodies long term.
It is true that the body has no essential need for carbohydrates. But the body does have an essential need for glucose, and in a state of glucose deprivation, it goes to great efforts to create the glucose it needs for however the shortage lasts.
Why do we need glucose?
- Glycogen restoration and muscle synthesis. Carbs raise insulin and encourage the muscles to absorb glucose to repair muscle fibers damaged during training. There is some debate in the scientific literature about whether carbs and protein need to be eaten together to sufficiently raise insulin levels enough for muscle protein synthesis or whether supplementing with the amino acid leucine with a source of protein works just as well (Figueiredo & Cameron-Smith, 2013). However, carbohydrates are necessary to quickly restore glycogen levels after a workout (Slater & Phillips, 2011).
- Mucus production, immune function and extra cellular matrix formation. L-glutamine is a major component of what comprises the gastrointestinal mucosal lining (Rao & Samak, 2012). However, glucose combines with proteins to create glycoproteins to form vital substances in the body, such as mucin and hyaluronan. When the body senses a deficiency in glucose, it often down-regulates mucin and hyaluronan production until it has access to more glucose. Mucin is a primary component of mucus, saliva and tears. This can result in constipation, leaky gut and compromised in an individual who is not careful to eat extra foods high in soluble fiber (Jaminet, & Jaminet, 2012). A compromised gut also reduces immune function (Campbell, 2014). Drs. Jaminet and Jaminet review the effects of glucose shortage on gut health pretty extensively in this compelling post on zero carb diets, mucus production and stomach cancer.
- Optimal thyroid function. A study that compared caloric starvation, protein modified sparing fast (a high protein diet) and a low carb, higher fat diet (Danforth et al., 1979) found that the active thyroid hormone triiodothyronine (T3) levels decreased in all groups and were instead converted to T3’s metabolic clearance, reverse T3. The most critical finding is that this occurred despite the subjects’ eating high calorie diets. Once fat calories were substituted with carbohydrates, however, T3 levels increased again. Low levels of active thyroid hormone are responsible for what is considered to be a decrease in metabolic function, as low levels of T3 are correlated with weight gain and metabolic syndrome (Clemens et al., 2011; Jonklaas et al., 2014). Cutting carbs too low for too long starts a process of energy conservation in the body which can include slowing the metabolism. This has benefits for anti-aging, but the detriments to suboptimal thyroid function include a number of non-essential functions that the body sometimes suspends in the absence of enough glucose, such as making mobilization of body fat stores impossible despite dieting efforts, hair loss, cold body temperature, brain fog, unstable moods, irregular heartbeats, insomnia or erratic sleep, lack of energy during the day, fatigue, hypothalamic amenorrhea, and other symptoms commensurate with starvation (Clemens et al., 2011; Jonklaas et al., 2014).
- Brain function. While fat is the preferred fuel source for most of the body, glucose is a preferred fuel for neuronal activity. The brain and nerves require approximately 20 calories per hour, sleeping or awake (Jaminet & Jaminet, 2012; Siegel et al., 1999), totaling between 480 calories per day. If this were to come from glucose, then the brain would need 120 grams glucose per day (Brandt, 1992). However, ketones can provide a maximum of 75% of this energy when in nutritional ketosis. Thus, in ketosis, the brain alone requires a minimum of 30 grams of glucose. Because this is an essential function, the body goes to great lengths to ensure that glucose is converted when in short supply so that the brain gets what it needs. This is the reason that many people develop a condition known as physiological insulin resistance, or PhIR. To ensure that the glucose available in the blood stays available for the brain’s essential needs and is not used for less essential functions when it is in short supply, the brain signals the body to leave glucose in the blood. Often, someone with PhIR will awake in the morning with high levels of blood glucose, often 100 mg/dL or higher. It can appear that you have high blood glucose but really this is a signal of glucose deficiency. This is a relatively new concept that has not been well defined in the scientific literature, but it has been well discussed in the low carb blogosphere. Most of those who review this concept below consider PhIR to be a normal—if not healthy—side effect of ketosis. The long term consequences of this adaptation are not entirely known. For more information, see the following blog posts written by people who are well regarded in the low carb community:
* https://freetheanimal.com/2014/10/physiological-resistance-carbohydrate.html http://high-fat-
How, then, can a person who demonstrates signs of glucose deficiency optimize ketosis while getting enough glucose to meet the body’s essential and some of the non-essential functions as well?
Ketosis signals the body to down regulate some functions because it considers being in a very low carb state to be temporary. If you keep carbs at 20 grams a day long term, though, you run the risk of losing some key functions in the body. There are a few simple ways to mitigate the effects of glucose deficiency:
- Eat l-glutamine, collagen and gelatin. The proteins are vital for constructing extra cellular matrix and intestinal mucus and can help to protect the body from dry eyes, dry mouth and leaky gut.
- Eat a high fiber diet from a variety of food sources. If you supplement with fiber, you provide the gut a limited source of prebiotic which will allow only certain gut flora to thrive. To ensure as diverse a population of gut flora as possible, try to vary your fiber consumption and sources. The best way to do this is to eat a wide range of plants high in fiber.
- Eat safe starches. This has become a popular practice among ketoers, who are experimenting with potato starch and plantain starch powders. This is one way to increase starch without increasing carbs in the diet.
- Eat a little glucose. Your individual carb tolerance level will vary greatly based upon the state of your immune health, but the body must utilize ketones for fuel in the absence of glucose. Even if your blood ketone levels are not detectable, your brain and many bodily functions can utilize ketones when glucose is in short supply. In other words, if you eat under 100 grams of carbs per day, glucose is in short supply and your body must utilize fatty acids to fuel some functions.
Generally speaking, I advise my clients who are exercising at least three days a week OR who have reached a healthy weight OR who experience any signs of metabolic or hormonal deficiency to eat a minimum of carbs (30-50 grams per day) for ongoing weight loss and to consider eating a healthy dose of carbs (150 grams) cyclically, at least once a week. Other clients can eat between 50-100 grams net carbs and remain in nutritional ketosis as confirmed by blood ketone tests (thanks to those who have been willing to test and share your results with me!). My clients who limit their carbs to 20 grams net carbs per day, as I did for several months, only stay at this level as long as they feel well. Everyone starts with the same number, but most do not stay here for long before symptoms of deficiency arise.
There are many ways to be in ketosis, and what works for one will not always work for everyone. I do not just watch the glucometer or the popular opinions—I have to pay attention to the symptoms my clients or I experience and I encourage you to do the same. Health, after all, is the reason that many of us began to eat a ketogenic diet in the first place and we can remain in a healthy state of ketosis as long as we follow the signs given by the body. I hope this post offers some freedom for those who have been interested in increasing carb levels but felt afraid to do so. My goal for you is always health above all, even if that means eating a diet that is not traditional for ketogenic eaters.
Atkins, R.C. (1992). Dr. Atkins New Diet Revolution. Harper-Collins Publishers Inc. New York, NY.
Brandt, M. (1992). http://www.rose-hulman.edu/~brandt/Chem330/EndocrineNotes/Chapter_5_Glucose.pdf
Campbell, A. W. (2014). Autoimmunity and the Gut. Autoimmune Diseases, 2014, 152428. http://doi.org/10.1155/2014/152428. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4036413/
Clemens, K., Payne, W., & Van Uum, S. H. M. (2011). Central hypothyroidism. Canadian Family Physician, 57(6), 677–680. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114669/
Danforth, E., Horton, E. S., O’Connell, M., Sims, E. A., Burger, A. G., Ingbar, S. H., … Vagenakis, A. G. (1979). Dietary-induced alterations in thyroid hormone metabolism during overnutrition. Journal of Clinical Investigation, 64(5), 1336–1347. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC371281/
Figueiredo, V. C., & Cameron-Smith, D. (2013). Is carbohydrate needed to further stimulate muscle protein synthesis/hypertrophy following resistance exercise? Journal of the International Society of Sports Nutrition, 10, 42. http://doi.org/10.1186/1550-2783-10-42
Jaminet, P. & Jaminet, S.C. (2010). Dangers of Zero Carb Diets, II: Mucus Deficiency and Gastrointestinal Cancers. http://perfecthealthdiet.com/2010/11/dangers-of-zero-carb-diets-ii-mucus-deficiency-and-gastrointestinal-cancers/
Jaminet, P. & Jaminet, S.C. (2012). Perfect Health Diet. Scribner Publishing. New York, NY.
Jonklaas, J., Bianco, A. C., Bauer, A. J., Burman, K. D., Cappola, A. R., Celi, F. S., … Sawka, A. M. (2014). Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement. Thyroid, 24(12), 1670–1751. http://doi.org/10.1089/thy.2014.0028. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4267409/
Physiological insulin resistance blogs:
Rao, R., & Samak, G. (2012). Role of Glutamine in Protection of Intestinal Epithelial Tight Junctions. Journal of Epithelial Biology & Pharmacology, 5 (Suppl 1-M7), 47–54. http://doi.org/10.2174/1875044301205010047. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4369670/
Ruper, S. (2012). Shattering the Myth of Fasting for Women: A Review of Female-Specific Responses to Fasting in the Literature. Paleo for Women: Stunningly Healthy Womanhood (website).
Siegel GJ, Agranoff BW, Albers RW, et al., editors. (1999). Basic Neurochemistry: Molecular, Cellular and Medical Aspects. 6th edition. Philadelphia: Lippincott-Raven. Available from: https://www.ncbi.nlm.nih.gov/books/NBK20385/
Slater, G. & Phillips, S.M. (2011). Nutrition guidelines for strength sports: sprinting, weightlifting, throwing events, and bodybuilding. J Sports Sci. 2011;29 Suppl 1:S67-77. https://www.ncbi.nlm.nih.gov/pubmed/21660839