Medical Perspectives | Cardio-Metabolic

March 06, 2021

Camille Ann R. Santos, MD

Would you believe that you can go on a diet eating bacon, lechon, and chicharon, and lose a significant amount of weight? Ketogenic diet, which is recently gaining popularity, has actually been around for almost a hundred years. This high fat, low carb diet which was originally intended to treat epilepsy is now used for weight loss and reduction of blood sugar level among diabetics. It works by putting the body in the state of "ketosis," which utilizes fats instead of sugar as the source of energy, turning the body into a fat-burning machine. A typical "keto diet"  would consist of 75% fats, 20% protein, and 5% carbohydrates.


Fat is not the culprit

One reason why the ketogenic diet has not quickly gained popularity as an effective weight loss intervention is probably its controversial high fat content. There are very few dieticians and physicians who would recommend this diet because of the belief that fats are linked to cardiovascular diseases. However, it has been proven by several scientific studies that a high fat diet is not bad for the body. In fact, a low carb/high fat diet was scientifically proven to decrease total cholesterol, triglyceride levels, LDL and VLDL levels and increase HDL levels.3,4,5,6,7 If fat is not the culprit, then why does it have such a bad rep? It turns out that the current widely accepted dietary guidelines were largely influenced by the sugar industry. In an article published by JAMA Internal Medicine, newly discovered documents revealed that, in the 1960s, a trade group called The Sugar Research Association paid Harvard scientists to produce  “scientific” studies that minimize the association between sugar and heart disease and shift the blame on fat and cholesterol.8 Last year, The New York Times published an article revealing that the Coca-Cola company has paid scientists to downplay the link between sugar and obesity.9


What are the benefits of a ketogenic diet?

Many scientific studies have showed positive effects of ketogenic diet. These include decreased body mass index (BMI) and cardiovascular disease risk,3,10,11 improved blood sugar control and insulin sensitivity amongst diabetics,12,13,14 decreased LDL and increased HDL levels,3,4,5,6,7 increased mental performance,15,16 and reduced acne.17 It has also been proven to improve symptoms in patients with epilepsy,18 Parkinson's disease,2 and polycystic ovarian syndrome (PCOS).19


How does ketogenic diet work?

When the body goes into a fasting state, it mobilizes the sugar stores in the liver and muscle. When the stores get depleted, fat stores are mobilized to form "ketones" which become the body’s new source of energy. In a ketogenic diet, the body thinks that it is in a fasting state due to the very low carbohydrate intake, so the metabolism shifts to ketosis and burns fat in the process.2


What are keto-friendly foods?

Only 20 to 50 grams of carbohydrates per day is allowed for the body to go into ketosis. Most keto advocates would recommend not taking any sources of carbohydrates at all so as to allocate the 20-50 g/day to "hidden carbs" found in foods such as vegetables and nuts. Table 1 lists down the foods that can and cannot be eaten in a ketogenic diet.


Table 1. Ketogenic diet food guide

Zero to Low Carb Foods


Moderate Carb Foods

EAT moderately

High Carb Foods


  • Meat (pork, beef, chicken, fish)
  • Egg
  • Butter
  • Full fat cream
  • Unprocessed cheese
  • Green leafy vegetables
  • Avocados
  • Mushrooms
  • Healthy oils (olive oil, coconut oil, avocado oil, etc)
  • Salt and pepper
  • Black coffee/tea
  • Sweeteners such as liquid stevia, erythritol



  • Nuts and seeds
  • Nightshades (cucumber, eggplant,
  • tomatoes, etc)
  • Full fat dairy products
  • Strawberries and blueberries
  • Any grains (rice, oatmeal, cereal, bread, pasta, etc)
  • All forms of sugar (white sugar, brown sugar, honey, agave, muscovado, etc)
  • Fruits except avocado
  • Beans or legumes
  • Root vegetables and tubers (potatoes, onion, carrots, etc)
  • Low-fat or diet products
  • Ketchup or other condiments high in sugar
  • Unhealthy fat such as vegetable oil
  • Alcohol
  • Artificial sweeteners such as Splenda, Equal


What are the side effects of ketogenic diet?

Some people have reported experiencing “keto flu” during the first couple of weeks of ketogenic diet. It may present as fatigue, headache, nausea, cramps, poor energy and mental function, increased hunger, sleep issues, digestive discomfort, and decreased exercise performance.

It is believed to be caused by the diuretic effect of a low carbohydrate diet, resulting in water and  electrolyte losses. It is advised to drink lots of water and ensure adequate sodium, potassium, and magnesium intake.


What are the effects of ketogenic diet on exercise?

Studies have shown that ketogenic diet does not affect the aerobic endurance of athletes, which makes it suitable for endurance training.20 It may cause symptoms of hypoglycemia in those who do exercises that require bursts of energy and strength. However, there have been personal accounts that doing strength training on a ketogenic diet is possible. This can be achieved once the body is “keto-adapted” which takes around 3 to 4 weeks.




  1. Wheless, JW. History of the ketogenic diet. Epilepsia 49 (2008): 3–5. doi:10.1111/j.1528-1167.2008.01821.x
  2. Gasior M, Rogawski MA, Hartman AL. Neuroprotective and disease-modifying effects of the ketogenic diet. Behavioural pharmacology. 2006;17(5-6):431-439.
  3. Bueno, Nassib Bezerra, et al. “Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials.” British Journal of Nutrition 110.07 (2013): 1178-1187.
  4. Brinkworth, Grant D., et al.“Long-term effects of a very-low-carbohydrate weight loss diet compared with an isocaloric low-fat diet after 12 mo.” The American journal of clinical nutrition 90.1 (2009): 23-32.
  5. Wood, Richard J., et al. “Carbohydrate restriction alters lipoprotein metabolism by modifying VLDL, LDL, and HDL subfraction distribution and size in overweight men.” The Journal of Nutrition 136.2 (2006): 384-389.
  6. Westman, Eric C., et al. “Effect of a low-carbohydrate, ketogenic diet program compared to a low-fat diet on fasting lipoprotein subclasses.” International journal of cardiology 110.2 (2006): 212-216.
  7. Dashti, H. M., Mathew, T. C., Hussein, T., Asfar, S. K., Behbahani, A., Khoursheed, M. A., … Al-Zaid, N. S. . Long-term effects of a ketogenic diet in obese patients. Experimental & Clinical Cardiology, 2004:9(3), 200–205.
  8. Kearns CE, Schmidt LA, Glantz SA. Sugar Industry and Coronary Heart Disease ResearchA Historical Analysis of Internal Industry Documents. JAMA Intern Med. 2016;176(11):1680–1685. doi:10.1001/jamainternmed.2016.5394
  9. O'Connor, Anahad. “Coca-Cola Funds Scientists Who Shift Blame for Obesity Away From Bad Diets.” The New York Times, The New York Times, 9 Aug. 2015, Accessed 3 Oct. 2017.
  10. Gardner, Christopher D., et al. “Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial.” Jama 297.9 (2007): 969-977.
  11. Hession, M., et al. “Systematic review of randomized controlled trials of low‐carbohydrate vs. low‐fat/low‐calorie diets in the management of obesity and its comorbidities.” Obesity reviews 10.1 (2009): 36-50.
  12. Yancy Jr, William S., et al. “A low-carbohydrate, ketogenic diet to treat type 2 diabetes.” Nutr Metab (Lond) 2 (2005): 34.
  13. Westman, Eric C., et al. “The effect of a low-carbohydrate, ketogenic diet versus a low-glycemic index diet on glycemic control in type 2 diabetes mellitus.” Nutr Metab (Lond) 5 (2008): 36.
  14. Hussain, Talib A., et al. “Effect of low-calorie versus low-carbohydrate ketogenic diet in type 2 diabetes.” Nutrition 28.10 (2012): 1016-1021.
  1. Yudkoff, M., Daikhin, Y., Melo, T. M., Nissim, I., Sonnewald, U., & Nissim, I. (2007). “The Ketogenic Diet and Brain Metabolism of Amino Acids: Relationship to the Anticonvulsant Effect.” Annual Review of Nutrition, 27, 415–430.
  2. Boden, Guenther, et al. “Effect of a low-carbohydrate diet on appetite, blood glucose levels, and insulin resistance in obese patients with type 2 diabetes.” Annals of internal medicine 142.6 (2005): 403-411.
  3. Paoli A, Grimaldi K, Toniolo L, Canato M, Bianco A, Fratter A, Nutrition and Acne: Therapeutic Potential of Ketogenic Diets. Skin Pharmacol Physiol 2012;25:111-117
  4. Henderson, C. Beth, et al. “Efficacy of the ketogenic diet as a treatment option for epilepsy: meta-analysis.” Journal of child neurology 21.3 (2006): 193-198.
  5. Mavropoulos JC, Yancy WS, Hepburn J, Westman EC. The effects of a low-carbohydrate, ketogenic diet on the polycystic ovary syndrome: A pilot study. Nutrition & Metabolism. 2005;2:35. doi:10.1186/1743-7075-2-35.
  6. Phinney SD. Ketogenic diets and physical performance. Nutrition & Metabolism. 2004;1:2. doi:10.1186/1743-7075-1-2.



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