Evidence Based Nutrition

The ketogenic diet has gained a lot of attention in recent years mainly due to the effects it has on weight loss but is the hype real about this diet, what are the facts and what is the science saying about keto.

Firstly, what is the ketogenic diet? Keto is a form of a low-carb diet however, keto places a strict limit on the number of carbs one is to consume. A typical ketogenic diet reduces carbs to 10% of macronutrient intake or lower, that is just around 50g of carbohydrates a day, to put that into perspective 50g of carbohydrates is the equivalent of 3 slices of whole-grain bread, 1 cup of chickpeas or 2 medium apples (24). Protein is limited at 20% while the rest, 70% or more, is fat (15). The keto diet was initially created over 100 years ago as an effective method to help control seizures in children and as a treatment for those with epilepsy and schizophrenia which it still is used for to this day (24, 9). However, the recent popularity of this diet has come not from its treatment benefits but the effect it has as a rapid weight loss strategy. The goal of this diet is to enter a state of nutritional ketosis so that the body will switch from using its glycogen stores to fat as a source of energy (22). The lack of glucose available places the body under stress placing it in a state of ketosis which is where the name comes from for the keto diet (6). Our bodies do this because our ancestors in our hunter-gatherer days would experience periods where food was not available, so this was a way of using stored energy (fat) to keep our bodies working, this also happens naturally during pregnancy and infancy (8). Ketosis is a metabolic state in which your body cannot get the preferred fuel of glucose therefore breaks down the fat in your body to turn them into ketones (8). Before this, however, your body will pull any stored glycogen from the liver and will temporarily break down protein to release glucose (6). Once fully depleted insulin levels decrease so then the body starts using fat, however, the brain requires 120g of glucose a day to function and cannot use fat as an energy source directly, so the liver makes ketone bodies from stored fat which are then used for energy in the absence of glucose (6, 18). This switch of prime energy source from carbohydrates to fat is exactly why this works as a weight-loss method if this can be sustained. There are some side effects at first when starting the keto diet that may prevent some from persevering with the diet. Your body has an adjustment period as carb intake drastically changes this could affect, workout performance, feelings of low energy, a cloudy mental state, hunger, sleeping problems, nausea and digestive discomfort (3). These effects are temporary and will pass after the first few weeks or you can ease into a keto diet by starting a low carb diet and reducing carbs until intake is 10% or lower so that these effects may not be so bad.

Benefits of Keto

We all have ketones these are chemicals produced in the liver which are sent out into the bloodstream for alternate uses of energy, for example, people with diabetes may have a higher level of ketones as glucose is not being absorbed due to not enough insulin being produced (8). The keto diet is another way to produce these ketone bodies but what effect does this have on the human body. 

It is mostly used these days as a weight-loss strategy, more specifically to reduce body fat. Studies do show that low carb diets such as the keto diet are effective weight-loss strategies, and the keto diet does this by using the stored fat as an energy source instead of the preferred carbohydrates. One hypothesis on why this works so well is because fats and protein increase the sense of fullness, therefore, reducing the need to overeat creating a calorie deficit (20). Limiting the food options may also create a caloric deficit which is key to effective weight loss success however all weight loss methods involve a calorie deficit so is the keto diet more effective than any other weight loss diet? Well, the keto diet can produce a more rapid weight loss compared to others which are due to what is previously mentioned about creating a fuller feeling, limiting options and switching prime fuel source to stored fat but I do not think this means it is a better weight loss diet (20). A meta-analysis (2013) of 13 studies that lasted longer than 1 year researched whether keto was better for weight loss compared to other diets. Bueno et al., (2013) found that the keto diet was associated with less than one kilogram of additional weight loss when compared to high-carbohydrate and low-fat diets strategies. This difference was statistically significant however, may not be considered clinically significant other studies have found the keto diet is effective but is not superior when it comes to weight loss compared to other diets (5).    

Studies have shown other benefits for using the keto diet, a study in 2012 on 23 older adults with mild cognitive impairment were randomised into either the high carb group or low carb group. After 6-weeks they found improvements in the low carb group for verbal memory performance, weight, waist circumference, fasting glucose, and fasting insulin. Concluding that dietary ketosis can enhance memory when there is mild cognitive impairment, therefore, could be useful for those at risk of Alzheimer’s disease (12). It is also thought that ketone body metabolism offers a metabolic advantage that could enhance exercise performance (9). An older study from Phinney et al., (1980) found in mildly obese untrained individuals could sustain prolonged exercise at a level of 60% V02 max with almost no carbohydrates. Also, after 6-weeks and a mean weight loss of 7.1kg, there was a significant increase (155%) in treadmill time when compared to baseline, from 168 minutes to 259 (19). 

Risks of Keto

Along with the benefits of keto also comes risks and some negatives of participating in this strict diet. Firstly, the keto diet is difficult to adhere to because of the restrictions and adjustment period, it is found that more than half are unable to stick with it therefore this diet may not be suitable for everyone (21). For example, this diet may be more challenging for a woman as they are more sensitive to changes in diet and weight (25). This diet could be risky for those with diabetes, some research has suggested it can help with blood sugar control however, others have shown it to increase blood cholesterol levels risking cardiovascular health (16). It may also increase the risk of ketoacidosis in those with diabetes which is when too many ketones are produced and floating around in the blood, this can cause the body to think it is starving when it is not and can lead to further complications which can be life-threatening (1, 8). Low carb diets may also, in the long term, increase blood cholesterol levels a study compared low carb diets and low-fat diets with the primary outcome being weight loss however data was collected on lipid levels. After 2 years results found no difference in weight loss, body composition or bone mineral density. However, the low carb group had a higher increase in HDL (good cholesterol) levels (23%) and was found to have less of a reduction in LDL cholesterol (bad cholesterol), although initially had a greater reduction in diastolic blood pressure compared to the low-fat group (7). A meta-analysis by Bueno et al., (2013) found that keto works for short term weight loss and can lower blood pressure however, it can also increase LDL cholesterol. 

If you are taking medications, you should consult your doctor before proceeding as the keto diet causes changes in body chemistry which can have major effects on any medications you may be taking (3). This shows how this diet is not for everyone like anything however the major concern for this diet is the long-term effects it has more specifically the deficiencies it may cause as it excludes an entire food group that has essential nutrients (6). The cost of not eating whole grains, fruits, legumes, high fibre foods that are some of the most health-promoting foods may do harm (10). As well as deficiencies other adverse effects potentially include nephrolithiasis, constipation, halitosis, muscle cramps, headaches, diarrhoea, restricted growth in children, bone fractures and pancreatitis (10). 

Long-Term

There has not been much research on the long-term effects of the keto diet on overall health and weight maintenance. Most of the long-term studies on this diet look at the impact the diet has on those with paediatric seizure disorders, although, one 10-year study found side effects of keto on epilepsy management which included constipation, high triglycerides, high cholesterol, diarrhoea, lethargy, iron deficiency, and vomiting (26). There is a worry about the long-term health effects of this diet, but not enough research has been done so we currently are not able to refer to the keto diet as a long-term strategy however, there is no doubt it works well as a short-term diet strategy (6). 

Keto for Athletes and Sport/Exercise Performance

Ketone bodies are used as an alternative source of energy to glucose for the brain and other tissues (2) and it has been suggested that they are more energy-efficient than glucose or fatty acids (9). Studies on whether the keto diet has any positive benefits on exercise performance have been mixed with some saying no difference in time to exhaustion (TTE) (23) and others saying similar TTE compared to high carbohydrate diets (19). Studies measured aerobic and anaerobic performance when on a keto diet and found no significant difference in increase of strength or power when compared to control therefore anaerobic performance does not benefit athletes or trained individuals on the keto diet (27). Aerobic performance has interesting findings as acute adaptation finds decreases in metabolic efficiency however, long-term endurance athletes take up keto as a lifestyle and remain competitive in marathons, ironman’s, triathlons, and cycling (13). Studies have also found that once adapted to the keto diet, endurance performance is not affected even compared to those on a high carbohydrate diet and in some cases is improved (14). Those on keto become better at using fat, fat oxidation improves, therefore the reason endurance performance is not affected and even in some cases improved could be due to fat being a slower, steady supply of energy whereas carbs are more instant and finite (9). On the other hand, studies have shown that those that train on keto diets then switch back to carbs have been found to be less efficient at using carbohydrates and could see a deterioration in performance (21). Studies are mixed on the benefits of keto in exercise and sports performance however long-term health effects remain a concern for both athletes and the general population that participate in keto. 

Conclusion

The science behind keto has shown the positives and negatives of this diet. It was originally used for those that suffer from epilepsy and seizures which works very well even to this day. However, it has gained popularity due to the improved fat oxidation which in turn causes rapid weight loss which there is no question it is also incredibly effective at doing if keto can be adhered. There is also evidence that keto can improve mental performance and potentially endurance performance. However, those with health conditions specifically diabetes may want to be careful, if ketone bodies become too high in the blood this can lead to some serious life-threatening problems. Also, those on any medication should seek advice from their doctor before proceeding. Keto is a hard diet to adhere to and may not be for everyone, this could interfere with social eating and harm your relationship with food. (24). People see a high-fat diet and use this as an excuse to adopt unhealthy eating over-indulging in processed meats and saturated fats which is known to be dangerous (6). A well planned out keto diet can be effective especially if the goal is weight loss however, the long-term effect of this diet is unknown, but researchers have their concerns. The concerns mainly include vital nutrient deficiencies, LDL and overall cholesterol-raising potential, also would not be a sustainable diet but more research is needed in the long term. Any diet that results in weight loss do so due to reduced calorie intake keto is no different therefore the focus should be on the quality of carbohydrates rather than cutting them out altogether this is not necessary for weight loss. As with any diet, weight is usually added back on once ending the diet period which is why changing the way you eat permanently by changing the types of foods you consume will in the long run be better for your weight management.

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References

1. Blanco JC, Khatri A, Kifayat A, Cho R, Aronow WS. (2019) ‘Starvation Ketoacidosis due to the Ketogenic Diet and Prolonged Fasting – A Possibly Dangerous Diet Trend’. Am J Case Rep.;20:1728-1731. Published 2019 Nov 22. doi:10.12659/AJCR.917226
2. Bowler, A. and Polman, R. (2020) ‘Role of a Ketogenic Diet on Body Composition, Physical Health, Psychosocial Well-Being and Sports Performance in Athletes: A Scoping Review’. Sports, 8(131) pp.1-16.
3. Brewster, J., (2017). ‘The Keto Diet: What is it and is it right for you?’. [Blog] I’ll Pump You Up, Available at: <https://illpumpyouup.com/keto-diet-is-it-for-you/&gt; [Accessed 17 January 2022].
4. Bueno NB, de MeloI S ,de Oliveira SL, da Rocha Ataide T. (2013). ‘Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials.’ Br J Nutr.;110(7):1178-1187. doi:10.1017/ S0007114513000548
5. Dyson, P., (2015). Low Carbohydrate Diets and Type 2 Diabetes: What is the Latest Evidence?. Diabetes Therapy, 6, pp.411-424.
6. F. Giroux, N., 2020. The Keto Diet and Long-Term Weight Loss: Is it a Safe Option?. Inquiries Journal, 12(10), p.1.
7. Foster GD et al. (2010). ‘Weight and metabolic outcomes after 2 years on a low-carbohydrate versus low-fat diet; a randomized trial’. Ann Intern Med. ;153(3):147–15
8. Habib, C., (2020). Ketosis and the Keto Diet. Naturopathic Currents, 80(3), pp.1-3.
9. Harvey, K., Holcomb, L. and Kolwicz, S. (2019) ‘Ketogenic Diets and Exercise Performance’. Nutrients, 11(2296) pp.1-16.
10. Joshi, S., Ostfeld, R. and McMacken, M., (2019). The Ketogenic Diet for Obesity and Diabetes—Enthusiasm Outpaces Evidence. JAMA Internal Medicine, 179(9), p.1163.
11. Joshi, S., Ostfeld, R. J., & Mcmacken, M. (2019). The Ketogenic Diet for Obesity and Diabetes—Enthusiasm Outpaces Evidence. JAMA Internal Medicine, 179(9), 1163. doi: 10.1001/jamainternmed.2019.2633
12. Krikorian, R., et al. “Dietary Ketosis Enhances Memory in Mild Cognitive Impairment.” Neurobiology of Aging, Vol. 33, No. 2 (2012): 425.e19–27.
13. McSwiney, F., Doyle, L., Plews, D. and Zinn, C., (2019). Impact Of Ketogenic Diet On Athletes: Current Insights. Open Access Journal of Sports Medicine, 10, pp.171-183.
14. McSwiney, F., Wardrop, B., Hyde, P., Lafountain, R., Volek, J. and Doyle, L., (2018). Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes. Metabolism, 81, pp.25-34.
15. O’connor, A. (2019, August 20). The Keto Diet Is Popular, but Is It Good for You? Retrieved from https://www.nytimes.com/2019/08/20/well/eat/the-keto-diet-is-popular-but-is-it-good-for-you.html
16. O’Neill B, Raggi P. (2020) ‘The ketogenic diet: Pros and cons. Atherosclerosis’.;292:119-126. doi:10.1016/j.atherosclerosis.2019.11.021
17. Paoli, A., Bianco, A. and Grimaldi, K. (2015) ‘The Ketogenic Diet and Sport: A Possible Marriage?’. Exercise and Sport Sciences Reviews, 43(3) pp.153-162.
18. Paoli, A., Rubini, A., Volek, J. S., & Grimaldi, K. A. (2013). Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. European Journal of Clinical Nutrition, 67(8), 789–796. doi: 10.1038/ejcn.2013.116
19. Phinney, S.D.; Horton, E.S.; Sims, E.A.; Hanson, J.S.; Danforth, E., Jr.; LaGrange, B.M. (1980). ‘Capacity for Moderate Exercise in Obese Subjects after Adaptation to a Hypocaloric, Ketogenic Diet’. J. Clin. Investig., 66, 1152–1161.
20. R, O., B, G. and KR., U. (2021) ‘Low Carbohydrate Diet’. In: StatPearls. StatPearls Publishing,.
21. Sankoff, D., (2021). Is the Keto Diet Healthy for Endurance Athletes?. [Blog] Training Peaks, Available at: <https://www.trainingpeaks.com/blog/is-the-keto-diet-healthy-for-endurance-athletes/&gt; [Accessed 17 January 2022].
22. Shaikh, S., Mohamed, M., Mujeeb, A., Shaikh, F. and Harris, B., (2020). Euglycemic Diabetic Ketoacidosis Precipitated by a Keto Diet: Importance of Dietary History in Diagnosis. Cureus, 12(9), p.e10199.
23. Shaw, D.M.; Merien, F.; Braakhuis, A.; Maunder, E.; Dulson, D.K. (2019). ‘Effect of a Ketogenic Diet on Submaximal Exercise Capacity and Efficiency in Runners’. Med. Sci. Sports Exerc. 
24. Shim, R., (2021). The Keto Diet: Part 1 What’s the evidence. [Blog] The Jiu Jitsu Dietitian, Available at: <https://www.rachshim.com/nutrition/the-ketogenic-diet-should-i-go-low-carb-to-make-weight&gt; [Accessed 17 January 2022].
25. Wells, S., 2020. Keto diet: Is it different for Women? A Guide. [Blog] Shawn Wells the ingredientologist, Available at: <https://shawnwells.com/2020/03/fasting-and-keto-guide-for-women-how-its-different-than-for-men-part-2/&gt; [Accessed 17 January 2022].
26. Wibisono, C., Rowe, N., Beavis, E., Kepreotes, H., Mackie, F. E., Lawson, J. A., & Cardamone, M. (2015). Ten-Year Single-Center Experience of the Ketogenic Diet: Factors Influencing Efficacy, Tolerability, and Compliance. The Journal of Pediatrics, 166(4). doi: 10.1016/j.jpeds.2014.12.018
27. Wilson, J.M.; Lowery, R.P.; Roberts, M.D.; Sharp, M.H.; Joy, J.M.; Shields, K.A.; Partl, J.; Volek, J.S.; D’Agostino, D. (2017). ‘The Effects of Ketogenic Dieting on Body Composition, Strength, Power, and Hormonal Profiles in Resistance Training Males’. J. Strength Cond. Res.