Answer: No—unless you do it for more than a few months. After a few months, the upfront metabolic and weight benefits will begin to reverse and new health problems arise. We know this with confidence. I raise this question once again because more and more people are coming to me reporting problems. It may take months, even years, but the long-term consequences can be quite serious.

Achieving ketosis by engaging in a very low-carbohydrate, high-fat lifestyle is—without a doubt—an effective means of losing weight, breaking insulin and leptin resistance, reversing type 2 diabetes and fatty liver, reducing blood pressure, reversing the inflammation of visceral fat, and may even cause partial or total remission of selected cancers. It means taking advantage of a natural physiological response to accelerate benefits.

So what’s the problem?

The problem comes when people remain ketotic for extended periods. We know with confidence that long-term ketosis poses substantial risk for health complications because thousands of children have followed ketogenic diets over the years as a means of suppressing intractable grand mal seizures unresponsive to drugs, seizures that can lead to irreversible brain damage if not stopped. A ketogenic diet reduces seizures by approximately 55%. Because seizures are a chronic problem, these kids maintain ketosis for months to years.

The health of these kids have been formally tracked. What happens to them beyond the reduction in seizures? A number of phenomena emerge:

They have high likelihood of calcium oxalate and uric acid kidney stones –Kidney stones are uncommon in childhood, yet these kids commonly have kidney stones. The risk in an adult on a prolonged ketogenic effort is therefore high, also. Kidney stones are not benign–they are painful and can occasionally result in kidney damage (increased creatinine, urinary tract infections, etc.)

–Kidney stones are uncommon in childhood, yet these kids commonly have kidney stones. The risk in an adult on a prolonged ketogenic effort is therefore high, also. Kidney stones are not benign–they are painful and can occasionally result in kidney damage (increased creatinine, urinary tract infections, etc.) Growth is stunted –Most of these kids fail to grow normally and fall into the 10th percentile for growth or less. Adults on a ketogenic diet are no longer growing, of course, but the growth impairment observed in children suggests that there is something fundamentally wrong with prolonged ketosis sufficient to impair normal growth.

–Most of these kids fail to grow normally and fall into the 10th percentile for growth or less. Adults on a ketogenic diet are no longer growing, of course, but the growth impairment observed in children suggests that there is something fundamentally wrong with prolonged ketosis sufficient to impair normal growth. There are occasional instances of cardiomyopathies (heart muscle diseases, heart failure) and sudden cardiac death –The immediate causes are unclear, though at least some cases are due to severe selenium deficiency. The picture is muddied by the fact that some kids were fed large quantities of corn oil in past as a means of maintaining ketosis. Nonetheless, it suggests further uncertainties with prolonged ketosis.

(heart muscle diseases, heart failure) and –The immediate causes are unclear, though at least some cases are due to severe selenium deficiency. The picture is muddied by the fact that some kids were fed large quantities of corn oil in past as a means of maintaining ketosis. Nonetheless, it suggests further uncertainties with prolonged ketosis. Constipation is the rule–as virtual elimination of dietary carbohydrates also means virtual elimination of prebiotic fibers that nourish bowel flora. Over time, this leads to metabolic distortions including a drop in HDL cholesterol, rise in triglycerides, rise in small LDL particles that lead to heart disease, rise in insulin resistance and blood sugar, rise in blood pressure, even if these parameters initially improved on the diet. This is also due to dysbiosis and lack of prebiotic fibers. While this has not yet been tracked in children, in adults we can expect that these distortions in bowel flora will, over time, also lead to heightened inflammation (bowel and elsewhere), diverticular disease (.e.g., diverticulitis), and colorectal cancer. Yes: prolonged ketosis can add substantially to risk for colon cancer. Other peculiar gastrointestinal complications of prolonged ketosis have also been observed, such as protein-losing enteropathies.

is the rule–as virtual elimination of dietary carbohydrates also means virtual elimination of prebiotic fibers that nourish bowel flora. Over time, this leads to metabolic distortions including a drop in HDL cholesterol, rise in triglycerides, rise in small LDL particles that lead to heart disease, rise in insulin resistance and blood sugar, rise in blood pressure, even if these parameters initially improved on the diet. This is also due to dysbiosis and lack of prebiotic fibers. While this has not yet been tracked in children, in adults we can expect that these distortions in bowel flora will, over time, also lead to heightened inflammation (bowel and elsewhere), diverticular disease (.e.g., diverticulitis), and colorectal cancer. Yes: prolonged ketosis can add substantially to risk for colon cancer. Other peculiar gastrointestinal complications of prolonged ketosis have also been observed, such as protein-losing enteropathies. Diminished bacterial species diversity—Not unexpectedly, deprivation of prebiotic fibers leads to a reduction in bacterial species diversity, especially beneficial Bifidobacteria, while E. coli proliferates. Recall that increased species diversity is a consistent marker for health.

While many of the problems that develop with prolonged ketosis may be addressed simply by minding intake of prebiotic fibers, not all are, such as selenium deficiency and stunted growth. (Note that the ideal intake of prebiotic fibers, the level we aim for in Wheat Belly and Undoctored programs, is 20 or more grams per day.) Some have argued that higher beta-hydroxybutyrate ketone levels that develop with a ketogenic diet is all you need to do to maintain healthy bowel flora, but this is a huge extrapolation that does not make sense in light of the newest insights into the microbiome and its metabolites. It ignores the role of hundreds of other microbial metabolites that are required and/or produced that are changed with prolonged deprivation of prebiotic fibers. Also, some have blamed the adverse long-term effects in kids on the seizure medications they take, but the side-effects of, say, drugs such as tegretol, valproic acid, or topiramate do not include the above phenomena.

If you want to use a ketogenic diet as a health tool, it would be wise to do so for no more than a few weeks at a time, as nobody knows how long is too long. And, of course, the period of time during which ketosis is safe can vary from individual to individual. Breaking ketosis is as easy as upping protein intake or having a glass of wine or whole piece of fruit.

Like the stress response, ketosis is a natural, physiological adaptation designed for short-term responses. In other words, an acute stress response to some danger or threat that involves increased adrenaline and cortisol release, increased heart rate and blood pressure, and heightened alertness is normal and can even save your life. But, if the stress response becomes chronic, as it may with divorce, prolonged caretaking of an impaired child or demented adult, PTSD, financial struggles, etc., then the stress response can have terrible health implications that include increased risk for Alzheimer’s dementia, heart disease, dysbiosis, inflammation, diabetes, and cancer. The same applies to ketosis: Acutely, ketosis is a normal physiological adaptation that serves us during periods of carbohydrate or calorie deprivation. Chronically, however, peculiar things happen with consequences that range from constipation, to selenium deficiency and cardiomyopathies, to colon cancer.

Another one of my concerns long-term is that many people are being persuaded to remain on a ketogenic diet over a long period. In 3, 5, or 10 years, we are going to see a sharp rise in colon cancer cases. People in conventional dietary circles will then point fingers at all of us engaged in unconventional dietary advice and we will be lumped together and labeled as dangerous fads. The key is to be smarter and to view ketogenic dieting as the short-term tool/response it is, not as a solution to all health struggles.

Also, be aware that, while diet can be an extremely powerful tool to regain control over many aspects of health, diet by itself remains insufficient for full health. Just as filling up the gas tank of your car with quality gasoline helps your car run well, but other aspects of your car need attention over time (change the oil, tune-ups, new tires on occasion, etc.), so it goes with diet. We must also pay attention to vitamin D and iodine status, the potential for common endocrine disruptions such as thyroid dysfunction, efforts to cultivate bowel flora, and other issues. Focus on diet as a start, not as an end.

So be ketotic—but just don’t stay ketotic for too long. Like an acute stress response, use it to your advantage but don’t allow it to become a chronic impairment of health.