What is a Keto Diet?
A keto (short for ketogenic) diet is a high fat, moderate protein, very low carbohydrate diet that places the body in a state of nutritional ketosis.
Ketosis is a metabolic state in which the body runs primarily on fats and ketone bodies, instead of carbohydrates (i.e. glucose).
Ketone bodies (or “ketones”, for short) are by-products of fat metabolism generated by the liver from the breakdown of adipose tissue (body fat) and dietary fats. Our cells can then oxidize (“burn”) these ketones for energy production.
You see, when you are in a state of nutritional ketosis, there is not enough glucose available (the primary source of energy for our cells) to meet demand. In order for you to keep living, the body switches to its “backup” energy system, which is fueled by fat and ketones (like BHB).
How to Set Up A Keto Diet?
Keto diets are structured such that they facilitate the transition to and maintain a state of nutritional ketosis.
In order to do this, you basically need to starve the body of glucose.
As such, keto diets have individuals consuming large amounts of dietary fat, “adequate” amounts of protein, and virtually no carbohydrates.
In terms of some “tangible” numbers, a typical keto diet may contain the following macronutrient ratios:
- Fat: 75%
- Protein: 15-20%
- Carbohydrates: 5-10%
Again, it’s worth reinforcing that these percentages are rough estimates and will vary from one individual to another.
For instance, the amount of carbohydrates one person can eat on a keto diet can drastically differ from how much another person does based on several factors including genetics, body comp, and physical activity levels.
For example, an individual who engages in high-intensity exercise multiple times per week will be able to consume a greater amount of carbohydrates and protein than a sedentary individual while still remaining in ketosis.
The reason for this is that intense physical activity (resistance-training, sprinting, rowing, etc.) is highly glycolytic, which is a fancy way of saying it uses glucose primarily for energy.
Since you’re burning through greater amounts of glucose and glycogen (stored glucose) when performing this type of exercise, you create a larger metabolic “sink” that can help absorb greater amounts of glucose, yet still remain in ketosis.
What Foods Can I Eat on a Ketogenic Diet?
Seeing as the typical keto diet contains ~70-75% of your daily calories from fat, expect to consume primarily fatty foods, some meat, and very little carbohydrates.
Here is a list of foods deemed “OK” by the majority of keto diet pundits:
- Fatty cuts of meat: Steak, bacon, dark meat poultry, sausage, bacon, etc.
- Fatty fish: Salmon, mackerel, tuna, trout, etc.
- Beef tallow
- Healthy oils: olive oil, MCT oil, coconut oil, etc.
- Nuts (in moderation): almonds, macadamia nuts, cashews, etc.
- Seeds (in moderation): pumpkin, chia, flax, etc.
- Low-carb vegetables: Broccoli, kale, spinach, peppers, squash, etc.
- Condiments: Herbs, spices, salt and pepper
What Foods Can I Not Eat on a Ketogenic Diet?
Following up on the previous section, basically any food that is high in carbohydrates (fruit, starchy vegetables, processed foods in the store) are off limits on the keto diet.
More specifically, if you want to follow a keto diet, avoid these foods:
- Grains: Wheat, barley, rye, rice, pasta, bread, oatmeal, cereal, etc.
- Most fruit: Except small servings of low-carb fruit like strawberries or blueberries
- Beans and legumes: black beans, pinto beans, lentils, chickpeas, peanuts, etc.
- Root vegetables: Potatoes, sweet potatoes, carrots, etc.
- Processed foods with added sugar: Soda, fruit juice, smoothies, cake, cookies, ice cream, candy, etc.
- Sugary sauces and condiments: ketchup, store-bought salad dressings, BBQ sauce, etc.
- Unhealthy fats: Processed vegetable oils, trans fats, etc..
- Alcohol: most mixed drinks contain a lot of sugar, which can prevent you from staying in or achieving ketosis
Benefits of the Keto Diet
Ketosis and keto diets have received a considerable amount of attention over the years from the scientific community and has been the subject of numerous studies, especially compared to some of the other fad diets lurking around the nutrition sphere.
Benefits documented in scientific research that can be attributed to being in a state of nutritional ketosis or following a keto diet for several weeks includes:[1,2,3,4]:
- Decreased blood sugar levels (as measured by HbA1c),
- Improvements in insulin sensitivity (as measured by HOMA-IR)
- Reductions in markers of inflammation (as measured by white blood cell count and C-reactive protein)
- Improved cholesterol profile
- Weight loss
- Decreased risk in certain types of cancer
- Potential reductions in epileptic seizures
- Increased longevity (in rodents)
Now, it bears mentioning that the benefits listed above are NOT exclusive to being in a state of ketosis or keto diets.
Similar improvements in body composition and metabolic health have been documented when individuals followed other forms of reduced calorie diets (such as higher carb, lower fat diets like the Mediterranean Diet), suggesting that the benefits of keto diets may be more attributed to individuals losing weight and increasing levels of physical activity than purely abandoning carbohydrates and eating high amounts of dietary fat.[5,6,7,8]
Drawbacks of the Keto Diet
As great as the hype surrounding the keto diet seems to be, it isn’t all rainbows and sunshine, especially during the first days and weeks.
You’ve likely consumed a relatively high carb diet for most of your life. As such, your body has optimized the carbohydrate metabolizing pathways over the years, which means when you all of a sudden pull the plug on the body’s primary source of energy, there’s going to be some “adjustments” that will occur as your body transitions to running on its alternative energy source.
During this “transitory” phase, the body will experience a state described as the “keto flu”, which basically involves feelings of:
- Brain fog
- Difficulty concentrating
- Muscle aches
Researchers have also observed a laundry list of other potential drawbacks when placing individuals on keto diets[10,11,12]:
- Bad breath
- Reduced athletic performance
- “Keto” Rash
- Muscle weakness
- Low blood sugar
- Poor sleep
Furthermore, any time a diet completely eliminates (or severely reduces) the intake of an entire macronutrient group, there is a significant increase in the chance for micronutrient deficiencies to occur.
In the case of keto, common nutrient deficiencies include:
- Biotin (B7)
- Folate (B9)
- Vitamin D
Finally, the ketogenic diet can be fairly meticulous (especially in the early days of the diet), which may not be ideal for those who prefer not to have to check their blood ketones or urinate on keto sticks every day.
The greatest factor that impacts whether a diet is successful (and therefore your ability to keep the weight off) is compliance.
For some people, the keto diet is not a sustainable way to live their lives or requires too much micromanagement. Plus, any diet that completely eliminates healthy foods like fruits, root vegetables, etc requires further inspection and consideration before jumping into head first.
Do I Need to Follow a Keto Diet to Burn Fat and Lose Weight?
No, you do not have to follow a keto diet in order to lose weight.
The reason for this is that the only “requirement” there is in order to lose weight is that you are in an energy deficit.
In other words, so long as you burn more calories per day than you consume, you will lose weight.
Much of the marketing for the keto diet centers around “increasing fat burning” and they’re not wrong. When you eliminate carbohydrates from the diet and replace it with dietary fat, your body has no choice but to burn fat for fuel...that is if it wants to remain alive.
Remember, “burning fat” is not the same thing as “losing weight.”
You can be burning fat 24 hours per day, but if you are not in an energy deficit, you will not lose weight, no matter how little carbohydrate or how much fat you eat.
Can you lose weight on a keto diet?
But, you can also lose weight following a lot of other diets that don’t completely eliminate an entire macronutrient.
The Bottom Line on the Keto Diet
The keto diet is a high fat, moderate protein, ultra low carb diet that places the body in a state of ketosis. It was originally developed for the treatment of epileptic seizures in children.
It has received increasing interest today due to some research it may support weight loss and improve markers of metabolic health. However, it remains to be seen if these improvements are a direct result of being in ketosis or is it a result of improving body composition and increasing levels of physical activity.
For some, a keto diet may be an enjoyable and sustainable way to eat. For others, the diet is tedious and restrictive, meaning the likelihood of sticking to it for the long term is unlikely.
- Bueno, N. B., de Melo, I. S. V., de Oliveira, S. L., & 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. The British Journal of Nutrition, 110(7), 1178–1187. https://doi.org/10.1017/S0007114513000548
- Dashti HM, Mathew TC, Hussein T, et al. Long-term effects of a ketogenic diet in obese patients. Exp Clin Cardiol. 2004;9(3):200–205.
- Allen BG, Bhatia SK, Anderson CM, et al. Ketogenic diets as an adjuvant cancer therapy: History and potential mechanism. Redox Biol. 2014;2:963–970. doi:10.1016/j.redox.2014.08.002
- Hallböök T, Ji S, Maudsley S, Martin B. The effects of the ketogenic diet on behavior and cognition. Epilepsy Res. 2012;100(3):304–309. doi:10.1016/j.eplepsyres.2011.04.017
- Clamp LD, Hume DJ, Lambert EV, Kroff J. Enhanced insulin sensitivity in successful, long-term weight loss maintainers compared with matched controls with no weight loss history. Nutr Diabetes. 2017;7(6):e282. Published 2017 Jun 19. doi:10.1038/nutd.2017.31
- Ross, R. (2003). Does Exercise Without Weight Loss Improve Insulin Sensitivity? Diabetes Care, 26(3), 944 LP – 945. https://doi.org/10.2337/diacare.26.3.944
- Le T, Flatt SW, Natarajan L, et al. Effects of Diet Composition and Insulin Resistance Status on Plasma Lipid Levels in a Weight Loss Intervention in Women. J Am Heart Assoc. 2016;5(1):e002771. Published 2016 Jan 25. doi:10.1161/JAHA.115.002771
- Ng, T. W. K., Watts, G. F., Barrett, P. H. R., Rye, K.-A., & Chan, D. C. (2007). Effect of Weight Loss on LDL and HDL Kinetics in the Metabolic Syndrome. Diabetes Care, 30(11), 2945 LP – 2950. https://doi.org/10.2337/dc07-0768
- Masood W, Uppaluri KR. Ketogenic Diet. [Updated 2019 Mar 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499830/
- D C Harvey CJ, Schofield GM, Williden M, McQuillan JA. The Effect of Medium Chain Triglycerides on Time to Nutritional Ketosis and Symptoms of Keto-Induction in Healthy Adults: A Randomised Controlled Clinical Trial. J Nutr Metab. 2018;2018:2630565. Published 2018 May 22. doi:10.1155/2018/2630565
- Gupta L, Khandelwal D, Kalra S, Gupta P, Dutta D, Aggarwal S. Ketogenic diet in endocrine disorders: Current perspectives. J Postgrad Med. 2017;63(4):242–251. doi:10.4103/jpgm.JPGM_16_17
- 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), 1030-1036.e1. https://doi.org/10.1016/j.jpeds.2014.12.018