Ketogenic Diet for Obesity and Diabetes: Do the Benefits Outweigh the Risks?

There’s growing popularity of the “fad” ketogenic diet for obesity and type 2 diabetes, but is it backed by evidence?

Type 2 diabetes and obesity are highly correlated and management of the two often requires major diet and lifestyle modifications. Weight loss is essentially achieved by caloric restriction, but over the years many “fad” diets have caught the attention of the public, including patients with type 2 diabetes. A few major trends have come and gone, including the Atkins diet and Paleo diet; currently the ketogenic diet is catching the attention of millions of people across the world. It is important for clinicians and patients with diabetes to understand the clinical evidence or lack thereof that supports the exercise of the ketogenic diet. As this diet, which emphasizes the elimination of nearly all carbohydrates, consuming moderate amounts of protein and high levels of fat, continues to gain popularity, there is concern in the medical community regarding the benefits vs risks from a lifestyle focused on these dietary habits.

The basis of the ketogenic diet is to put and maintain the body in a state of ketosis. This is different from diabetic ketosis, when the body produces excess amounts of ketones due to a lack of insulin production. On the ketogenic diet, the body enters physiological ketosis within 3-4 days during which stored fat is broken down to ketones for fuel in the absence of carbohydrates. This diet often leads to successful weight loss from the burning of fat, the inherent reduction of calories associated with reduced carbohydrate intake, and increased satiety from ketones in the blood.

Type 2 diabetes is characterized by carbohydrate intolerance due to insulin resistance and deficiency. Steady, reduced consumption of carbohydrates, such as in the ketogenic diet, can improve glycemic control. Also, subsequent weight loss can aid in improving insulin resistance. While this is all true, it is important to note that there is little evidence showing that ketogenic diets improve glycemic control, independent of weight loss. One non-randomized study of the ketogenic diet in patients with type 2 diabetes displayed a 1.3% reduction in HbA1C over one year, but its non-randomized and self-selected population does not offer very dependable conclusions. A meta-analysis of randomized long-term studies compared ketogenic diets to low-fat diets for weight loss in patients with type 2 diabetes and no difference between the groups was reported for glycemic control. Another recent study compared three equicaloric diets with varying carbohydrate intake amounts, and the low-carbohydrate diet displayed the largest decrease in metabolic syndrome risk factors in patients with obesity and metabolic syndrome.

While reduction of carbohydrate intake can be of great benefit to patients with type 2 diabetes, there are many benefits that come from healthful carbohydrates: those that contain high content of fiber and are unrefined. When discussing carbohydrates, it is easy to automatically think of white rice, pasta, white bread, high sugar cereals, fruit juices and French fries and immediately associate eliminating carbohydrates with being beneficial, but think again. There are tremendous benefits from healthy carbohydrates such as whole grains, fruits, and legumes. A systematic review found that consumption of whole grains was associated with dose-dependent reduction in risk for coronary heart disease, cardiovascular disease, total cancer and all-cause mortality. While similar evidence has been found for fruits and legumes as well, almost all nutrition experts recommend that nearly all refined carbohydrate foods be avoided, while including healthful carbohydrates in the daily diet of all persons. Currently, with the trends of low or no carb diets, such as the ketogenic diet, there is not much distinction between healthy and unhealthy carbohydrates, leading to assumptions that all carbohydrates are bad. This poses a risk for patients to miss out on significant health benefits from high fiber carbohydrates including good digestive health, improved blood glucose levels, potential decreased risk of colorectal cancer, improved skin health and cardiovascular outcomes.

Additional risks associated with the ketogenic diet include several, ranging in severity. Many reports of the “keto flu” describe the induction phase as a period of fatigue, weakness and gastrointestinal disturbances. Effects from a literature review of ketogenic diets for treatment of pediatric epilepsy report side effects as severe as cardiac arrhythmias from selenium deficiency. Other documented adverse effects include constipation, diarrhea, nephrolithiasis, headaches, restricted growth, bone fractures, and multiple vitamin and mineral deficiencies.

While the trend of the ketogenic diet continues, it is important for clinicians and patients with type 2 diabetes and obesity to be aware of the benefits vs. risks, as well as the lack of supporting evidence that the keto diet can help treatment of disease.

Practice Pearls:

• The ketogenic diet, based on very low carbohydrate, moderate protein, and high fat intake, has been growing extremely popular, sparking interest in patients with type 2 diabetes and obesity.
• There is currently no evidence to prove that ketogenic diet improves glycemic control, independent of weight loss, and patients may be missing crucial dietary nutrients from skipping healthful carbohydrates.
•  It is important to educate patients on the benefits vs risks of the ketogenic diet, based on evidence based medical literature.

References:

Joshi, Shivam. “The Ketogenic Diet for Obesity and Diabetes.” JAMA Internal Medicine, 15 July 2019, jamanetwork.com/journals/jamainternalmedicine/fullarticle/2737919.

Paoli, Antonio. “Ketogenic Diet for Obesity: Friend or Foe?” International Journal of Environmental Research and Public Health, vol. 11, no. 2, 2014, pp. 2092–2107., doi:10.3390/ijerph110202092.

Bueno  NB, de Melo  IS, de Oliveira  SL, da Rocha Ataide  T. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials.  Br J Nutr. 2013;110(7):1178-1187. doi:10.1017/S0007114513000548

Hallberg  SJ, McKenzie  AL, Williams PT,  et al. Effectiveness and safety of a novel care model for the management of type 2 diabetes at 1 year: an open-label, non-randomized, controlled study.  Diabetes Ther. 2018;9(2):583-612. doi:10.1007/s13300-018-0373-9

 Amber Satz, PharmD Candidate, LECOM School of Pharmacy