The latest diet craze is focused on low-carbohydrate, and very-low-carbohydrate (aka the ketogenic/keto) diets; hailed as eating plans that deliver weight loss, reduced cravings, improved insulin response, and lower A1C results. While this may be a quick fix, at inception, the results, and adherence, can be short-lived.
What is low carb
Confusion exists surrounding these diets because low carb has been poorly defined in the research. Studies range from 45% calories from carb – all the way down to 20 grams /day. The American Diabetes Association (ADA) nutrition consensus paper, defines low carb as 26-45% of calories from carbohydrates and very-low-carb as less than 26%. A meal plan is considered “keto” or ketogenic, when carb reserves are so low the body must break down fat for energy, releasing a by-product called ketones. This can occur in the very-low-carb diets (less than 50 grams carb/day).
In 2019, the Journal of Clinical Lipidology provided a review of current evidence and recommendations on very-low-carbohydrate (including keto) diets. They found the keto diet may improve triglycerides and HDL cholesterol, blood sugar control, and reductions in diabetes medications. However, variable effects were found on LDL cholesterol. However, after one year, A1C levels were the same as those who followed a low-calorie diet. At approximately two years, there were no differences for most cardiometabolic risk markers.
While some studies of very-low-carb diets have been carried out for two years, long-term evidence is lacking. Research often falls short because control groups are missing, and such a restrictive diet can be challenging to follow long term leading to high drop-out rates.
In the 2018, article, “Ketogenic diets: boon or bane?” published in the Indian Journal of Medical Research, the author states, “Long-term low-carbohydrate diets with increased fat consumption have been hypothesized to stimulate inflammatory pathways, oxidative stress, and promote biological ageing … Furthermore, many feel weak and frustrated and start increasing the carbohydrate intake, and soon they are back to their original weight and diabetes control.”
Many very-low-carb dieters report side effects (usually from dehydration) that can last anywhere from one day to one week including: light headedness, difficulty exercising, poor sleep, muscle cramps, irritability, mood swings, constipation, vomiting, fatigue, hypoglycemia, increased blood uric acid (a risk factor for gout), and vitamin and mineral deficiencies. Emergency room visits and admissions for dehydration, electrolyte disturbances, and hypoglycemia are not uncommon.
Not for Everyone
While many people are experimenting with very-low carb diets, it is important individuals are aware these diets can fall short nutritionally. The majority of fruits, starchy vegetables, pulses, whole-grains, and dairy products are restricted, which provide rich sources of nutrients, antioxidants, and phytochemicals not found in fats or proteins. Additionally, fiber intake, without these foods, is often inadequate in very-low carbohydrate diets. Fiber is critical food for the gut bacteria and short-chain fatty acids which help control inflammation, support immune function, and maintain overall gut health. Furthermore, the types of fats consumed should be considered carefully. Depending on the source for recipes / advice, the type of fat promoted may come from saturated sources like coconut oil, palm oil, bacon, and butter.
The ADA does not recommend very-low-carb eating plans for people with chronic kidney disease, eating disorders, women who are pregnant, or lactating, or people using specific diabetes medicines. Adopting a very-low-carb diet can also lead to hypoglycemia and careful monitoring of blood sugar is recommended. The Academy of Nutrition and Dietetics adds these diets are not appropriate for those with pancreatic disease, liver conditions, thyroid issues, or gallbladder disease (or those who have had their gallbladder removed).
With the various elements to consider, all individuals considering a restrictive carbohydrate diet, should discuss it with their healthcare provider and registered dietitian first.
While very-low-carb diets are generating a buzz for quick results, the short-term benefits and possible health risks may make these diets more difficult, or risky, to adhere to as a lifestyle. More research must be conducted before we can truly understand the full potential and/or pitfalls this diet could provide.
By Mandy Seay, RD, LD, CDCES
Evert AB, Dennison M, Gardner CD, et al. Nutrition therapy for adults with diabetes or prediabetes: a consensus report. Diabetes Care 2019;42:731–54. 10.2337/dci19-0014
Kirkpatrick CF, Bolick JP, Kris-Etherton PM, Sikand G, Aspry KE, Soffer DE, et al. Review of current evidence and clinical recommendations on the effects of low-carbohydrate and very-low-carbohydrate (including ketogenic) diets for the management of body weight and other cardiometabolic risk factors: a scientific statement from the National Lipid Association Nutrition and Lifestyle Taskforce. J Clin Lipidol. In review.
Joshi S., Ostfeld R.J., McMacken M. The Ketogenic Diet for Obesity and Diabetes-Enthusiasm Outpaces Evidence. JAMA Intern. Med. 2019;179:1163–1164. doi: 10.1001/jamainternmed.2019.2633.
Gordon B. What is the Ketogenic Diet? https://www.eatright.org/health/weight-loss/fad-diets/what-is-the-ketogenic-diet. Published May 15, 2019. Accessed February 23, 2020.