The ketogenic diet has hit the internet with a vengeance, replacing paleo as this years favorite fad diet. Both fitness enthusiasts and the everyday person alike have been turning to keto as a way to lose weight and get their eating back on track. Ketogenic marketing is wrapped in a powerful narrative claiming that keto can adapt your body to lose fat 24/7 and help boost brain function, but how much of this narrative is actually aligned with the truth?

What is the ketogenic diet?

The ketogenic diet is a low carb diet which replaces the calories traditionally consumed through carbohydrates with calories from fat. Here is a breakdown of the macronutrient shift:

Macronutrient Recommendations by the 2015 Dietary Guidelines

55% Carbohydrates

20% Protein

25% Fat

The Ketogenic Diet

5% Carbohydrates

20% Protein

75% Fat

Physiology of the Ketogenic Diet

When someone eats a very low carb diet, their blood glucose and insulin levels drop dramatically. This drop in insulin triggers the enzyme lipase to break down stored fatty acids, which are then delivered to and processed by the liver to create ketones. These ketones can then in turn be used by the body to make energy in the absence of glucose. This state of producing ketones in for energy is known as ketosis.

Historic Use of the Ketogenic Diet

The ketogenic diet was invented in the early 1920s as a medical cure for seizures in children. Some research has shown that the production of ketones can influence neurotransmitter activity in a way that reduces the chances of epileptic seizures. It was a last ditch attempt for children who could not be treated effectively by anti-epileptic seizure medication. A clinical trial at Great Ormond Street Hospital in 2008 showed 40% of child participants who started the diet had the number of their seizures reduced by over half and were able to reduce their medication.

The Ketogenic Diet for Weight Loss

Recently, the ketogenic diet has become a diet used for weight loss; the theory being that a state of ketosis causes an increase in fatty acid breakdown which leads to increase in fat loss. Additionally, there is research showing that a state of ketosis decreases the body’s level of ghrelin, the hormone that causes hunger symptoms. This is likely one reason why many people who try the ketogenic diet report feeling better than they ever have on any other fad diet.

Although the theory behind keto causing weight loss seems promising on paper, the current research on the efficacy of the ketogenic diet on long term weight loss is much less promising. It is undeniable that, at least initially, the keto diet will result in weight loss. This should be expected, as most people who abruptly eliminate an entire food group will in turn eat less than they did before, because their food choices are much more limited. It is also the case that keto will result in a drastic loss of water weight because glycogen, the storage form of glucose, holds and stores water. Depleting glycogen stores with a low carb diet will inevitably result in considerable water loss.

Water weight loss is one thing, but when people say they want to lose weight what they really mean to say is that they want to lose fat, and keto may not be the best method of fat loss. One study researching fat loss in individuals following keto found that the participants following the ketogenic diet lost about the same amount of fat as the participants following a more traditional diet with same number of calories. Although the ketogenic diet resulted in more rapid body weight loss initially, the total fat loss between both participant groups was essentially equal. This suggests that any long term weight loss seen through following keto is more so due to a calorie deficit as opposed to ketosis or hunger suppression.

Concerns Surrounding the Ketogenic Diet

Nutrient Deficiencies

Several essential micronutrients are found in plant based foods. If your consumption of fruits and vegetables is severely limited, you are at a higher risk for many micronutrient deficiencies. A few micronutrients to be particularly aware of while following keto include biotin, pantothenic acid, vitamin K, sodium, and potassium. Lack of fiber is also a concern.

Hyperlipidemia

Long term adherence to an extremely high fat diet may increase your risk of hyperlipidemia, particularly if the fat you’re consuming is primarily saturated fat.

Keto Flu

Some people who try keto complain of symptoms referred to as keto flu; fatigue, dizziness, irritability, difficulty sleeping, and sugar cravings. Thankfully, the symptoms usually only last the first few weeks.

Loss of Muscle Mass

Insulin promotes muscle growth by essentially “unlocking” the muscle to allow amino acids in. The drop of blood insulin associated with keto may hinder this process, and lead to loss of muscle mass. Alternatively, a visible loss of muscular size may instead be due to the water lost with depleted muscle glycogen. At this point, it is unclear how much of a concern loss of muscle mass is, however, it is something to keep in mind.

Sustainability

Sustainability is a concern of any elimination diet; how long can someone realistically limit their food choices so dramatically? The answer is different for everyone, but it is important to determine the practicality for yourself, particularly when considering how your food choices may influence social interactions such as visiting restaurants or attending parties.

The biggest problem we have with the current research on keto is that little of it examines long term effects past much more than 6 months. For this reason, it is difficult to determine with confidence the potential health benefits/complications of the diet.

Takeaways

For long term success at weight loss, it is easiest to simplify your diet as much as possible. Adding more fruits and vegetables to your diet as opposed to restricting major food groups has repeatedly proven weight loss results without adverse consequences.
Stop looking for a quick fix. Keto is appealing because it is fast acting, but it is not likely to result in the weight loss you are looking for.
More long term research is needed to confidently define the health consequences of the ketogenic diet, particularly its effect on sustainable weight loss.

References:

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 Oct;110(7):1178-87.

Erlanson-Albertsson, C, and J Mei. “The Effect of Low Carbohydrate on Energy Metabolism.”International Journal of Obesity, vol. 29, no. S2, 2005, doi:10.1038/sj.ijo.0803086.

Gibson, A. A., et al. “Do Ketogenic Diets Really Suppress Appetite? A Systematic Review and Meta-Analysis.” Obesity Reviews, vol. 16, no. 1, 2014, pp. 64–76., doi:10.1111/obr.12230.

Liu, Yeou-Mei Christiana, et al. “Can Children With Hyperlipidemia Receive Ketogenic Diet for Medication-Resistant Epilepsy?” Journal of Child Neurology, vol. 28, no. 4, 2013, pp. 479–483., doi:10.1177/0883073813476140.

Paoli, A, et al. “Beyond Weight Loss: a Review of the Therapeutic Uses of Very-Low-Carbohydrate (Ketogenic) Diets.” European Journal of Clinical Nutrition, vol. 67, no. 8, 2013, pp. 789–796., doi:10.1038/ejcn.2013.116.

Sumithran, P, et al. “Ketosis and Appetite-Mediating Nutrients and Hormones after Weight Loss.” European Journal of Clinical Nutrition, vol. 67, no. 7, 2013, pp. 759–764., doi:10.1038/ejcn.2013.90.

Wheless, James W. “History of the Ketogenic Diet.” Epilepsia, vol. 49, 2008, pp. 3–5., doi:10.1111/j.1528-1167.2008.01821.x.

Yancy, William S., et al. “A Low-Carbohydrate, Ketogenic Diet versus a Low-Fat Diet To Treat Obesity and Hyperlipidemia.” Annals of Internal Medicine, vol. 140, no. 10, 2004, p. 769., doi:10.7326/0003-4819-140-10-200405180-00006.