So many people have asked me recently about the ketogenic “keto” diet and the benefits — and the drawbacks — of severe carbohydrate restriction.

Is the keto diet the “magic pill” for ending weight and health struggles, as a certain Netflix documentary would like us to believe?  As you’ll see, absolutely not. What’s more, keto diets can actually be quite harmful to your health.

What happens in your body when you’re on a ketogenic diet

A ketogenic diet is one that limits carbohydrate intake to the point at which the “starvation response” is triggered in the body. This starvation response mobilizes stored fat and breaks it down as a way to produce acetyl coenzyme A (CoA) — the body’s backup energy source in place of the glucose it isn’t getting when we don’t or can’t eat carbohydrates.

Most standard keto diets pair the low carbs with high fat and moderate protein intake, but when weight loss is the goal, there’s often a limit on fat intake as well to encourage reduced calorie intake (since fatty foods are typically higher in calories too).

The benefits of ketogenic diets

Keto diets do have legitimate benefits when it comes to weight loss, but as you’ll see below, the risks may outweigh the benefits.

Short-term weight loss. Reducing carbohydrate intake and monitoring caloric intake will offer the body only one place to turn for energy: body fat stores. A strict ketogenic regimen can produce steady and reliable weight loss in most otherwise healthy overweight adults in the course of a few months. (I’ll get to the “but…” in a moment.)

Short-term improvement in blood sugar. Individuals who eat a standard diet who do not have diabetes, prediabetes, or insulin resistance tend to have blood glucose levels in the range of 80–120 mg/dL. Those on a ketogenic diet, however, typically have blood glucose levels between 65–80 mg/dL. Before you say, “holy hypoglycemia!” keep in mind that the body adjusts to these levels in part by producing more CoA.  So for someone who might be on the borderline of diabetes and wants to better manage blood sugar levels, a keto diet can be a good place to start — although there’s a “but…” associated with this as well!

When keto diets become harmful to your health

While we evolved to use glucose as our primary energy source, our ancestors couldn’t always rely on carbohydrate-rich plant foods being available all the time. So the ability to use fats as a source of glucose (whether from animal foods they ate or by burning their own adipose tissue during times of famine) was an effective short-term backup plan. The operative phrase is “short-term.”

Because there are definitely harmful long-term effects of ketones in the body:

Keto diets acidify the body. Ketosis, which is the name for production of ketones in general, and its more dangerous, dysfunctional variant ketoacidosis (a life-threatening buildup of ketones that happens most often in diabetic individuals) results in lower blood pH — in other words, acidosis.

I’ve talked before about how acid-forming foods can be harmful to bones, but chronic low-grade acidosis has health impacts well beyond bone health. It can potentially increase risk of cancer development and progression; increases production of the stress hormone cortisol; and potentially causes the development of kidney disorders such as kidney stones (Robey, 2012; Pizzorno, 2015).

Keto diets can promote fatty liver disease and insulin resistance. This is where those two “but…” caveats from earlier come in… There is evidence in mice — and to a lesser extent in humans — that long-term use of keto diets promotes development of nonalcoholic fatty liver disease and (paradoxically) insulin resistance (Schugar & Crawford, 2012; Ellenbroek et al., 2014). The increase in insulin resistance is likely related to longer-term increases in cortisol.

So, while the short-term benefit for blood sugar and other cardiovascular makers exists with keto diets, in the long term, regulating blood sugar and other aspects of cardio health is better achieved through a balanced diet paired with regular exercise.

Keto diets are NOT the best choice for long-term weight loss

Although a keto diet may be a good starting point for shaving off pounds, it probably isn’t something you want to stick with over time — more than, say, a few months — especially if you have a family history or personal tendency toward diabetes, insulin resistance, kidney dysfunction or fatty liver disease.

This includes finding ways to gradually include a healthier set of carbs into your food choices. My favorites are nutrient-rich, alkalizing starchy vegetables like root vegetables and squash, which are full of complex carbohydrates, rather than the standards of bread and sweets.

References

Ellenbroek JH, van Dijck L, Tons HA, Rabelink TJ, Carlotti F, Ballieux BE, de Koning EJ. Long-term ketogenic diet causes glucose intolerance and reduced β- and α-cell mass but no weight loss in mice. Am J Physiol Endocrinol Metab. 2014 Mar 1;306(5):E552-8. doi: 10.1152/ajpendo.00453.2013. Epub 2014 Jan 7.

Kosinski C, Jornayvaz FR. Effects of ketogenic diets on cardiovascular risk factors: Evidence from animal and human studies. Nutrients. 2017 May 19;9(5). pii: E517. doi: 10.3390/nu9050517.

Kosinski C, Jornayvaz FR. [Ketogenic diets: the miraculous solution?] Rev Med Suisse. 2017 May 31;13(565):1145-1147.

Nei M, Ngo L, Sirven JI, Sperling MR. Ketogenic diet in adolescents and adults with epilepsy.
Seizure. 2014 Jun;23(6):439-42. doi: 10.1016/j.seizure.2014.02.015. Epub 2014 Mar 12.

Paoli A, Rubini A, Volek JS, Grimaldi KA. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. Eur J Clin Nutr. 2013 Aug;67(8):789-96. doi: 10.1038/ejcn.2013.116. Epub 2013 Jun 26.

Pizzorno J. Acidosis: An old idea validated by new research. Integr Med (Encinitas). 2015 Feb; 14(1): 8–12.

Robey, IF. Examining the relationship between diet-induced acidosis and cancer. Nutr Metab (Lond). 2012; 9: 72. Published online 2012 Aug 1. doi:  10.1186/1743-7075-9-72

Schugar RC, Crawford PA. Low-carbohydrate ketogenic diets, glucose homeostasis, and nonalcoholic fatty liver disease. Curr Opin Clin Nutr Metab Care. 2012 Jul;15(4):374-80. doi: 10.1097/MCO.0b013e3283547157.