Do Calories Matter on a Keto Diet?

Picture of nutrition facts label highlighting calories

Among the numerous health and performance benefits of the ketogenic diet, weight loss is rapidly emerging as a prime incentive to go keto! The fat burning effects of the low-carb, high fat keto diet are driven by nutritional ketosis - a normal metabolic state marked by high levels of ketones in the blood. Nutritional ketosis occurs when low insulin levels resulting from carb restriction prompt the release of body fat to be burned or converted to ketones for energy. Extra dietary fat also contributes to ketone production. 

Since “what you eat” on the keto diet is central to its weight loss effects, is “how much you eat” important? Is it necessary to track calories on the keto diet?

Let’s backup a bit and first take a close look at the fierce debate surrounding energy balance, i.e, “calories in, calories out”.....

Are all Calories Created Equal?

The first law of thermodynamics (or the law of conservation of energy) states that energy cannot be created or destroyed. When applied to weight control, this law translates to the basic formula: 

weight gain = energy (calories) in - energy (calories) out

According to this traditional viewpoint, a calorie is a calorie. To lose weight, you must create a calorie deficit by either eating less or burning more. To gain weight, you need to add calories.

In other words, calories are all that matters. The type of food you eat is unimportant.

However, the opposing (and more realistic) position maintains that, while calories still count, the type of food you eat impacts the amount of energy you expend, and the way you expend energy affects what foods you eat. Consider, for example, the thermic effect of food. It takes significantly more energy to process and digest protein than carbohydrate or fat. In one study, twice as much energy was expended after meals on a high-protein diet versus a high carbohydrate, low-fat diet.1 

Another study compared the effects of three diets differing in macronutrient (carb, fat, protein) composition on energy expenditure during weight loss maintenance. Weight loss causes resting energy expenditure (metabolic rate) to go down, which predisposes to weight regain. Results of the study showed that the very low carb (and highest protein) diet had the LEAST effect on reducing resting energy expenditure following weight loss.2 

The loss of energy as heat through the thermic effect of food is consistent with the second law of thermodynamics, which states that some energy is always lost in any chemical reaction. In other words, you can’t break even. The concept of “ a calorie is a calorie” defies this law.3 

Pie Chart of Thermic Effect of Food

Apart from the thermic effect of food, hormonal changes associated with different types of food are also important. Diets that are high in carbs cause increased secretion of the hormone insulin. Whereas elevated insulin levels drive fat storage, low insulin promotes fat burning.4,5 

It’s clear, then, that the type of food you eat can affect energy expenditure and fat loss. Now let’s flip that. Can burning calories through physical activity influence what you eat and whether those ingested calories are stored or burned for energy? Yes, by affecting food reward regions in the brain. Acute bouts of aerobic exercise have been shown to significantly suppress appetite and hunger while increasing satiety and fullness.6 Exercise in the form of resistance (weight) training can enhance insulin sensitivity,7 which results in reduced insulin secretion.8 Less insulin favors fat burning over fat storage.

To sum up, weight loss results from burning more calories than you consume. Calories matter. However, the macronutrient composition of the calories you eat matters more. Different foods have substantially different metabolic and hormonal effects in the body. What you eat (as well as how you burn calories) can change how much you eat and whether you will store or burn those calories. Therefore, all calories are NOT created equal.

Now let’s go back to the ketogenic diet….

Keto and Weight Loss

A review of 13 randomized controlled trials (1415 patients) found that people on the ketogenic diet lost significantly more weight than people on low fat diets. They also kept the weight off for 12 months or more.9 While the diets in these studies contained no more than 50 grams of carbohydrate (in accordance with a typical keto diet plan), low-carb diets with more generous amounts of carbohydrate (≥ 120 gm/day) showed similar results (more weight loss with low-carb than low-fat) in a review of 17 randomized controlled trials (Sackner-Bernstein2015). More recently, type 2 diabetics lost 12% of their body weight after one year in diet-induced ketosis.10 

Some people will argue that weight loss from low-carb diets is mostly water weight. While initially there is certainly water loss from glycogen depletion, studies have demonstrated that weight loss from a keto diet lasting a few weeks or longer is predominantly fat.5,11 

There’s no disputing it....the keto diet is very effective for promoting major weight loss...but how? 

Picture of Lettuce Next to a Skillet Filled with an Omelette

Two general theories have been put forth to explain the superior weight loss associated with the low-carb, keto diet...

Metabolic Advantage

According to one hypothesis, low-carb diets have a distinct “metabolic advantage” over diets with higher carbohydrate content (calories being equal).3 This metabolic advantage is essentially an increase in the expenditure of energy (calories) on the low-carb diet. Factors that may account for this higher rate of calorie burning include:

  1. Higher energy costs associated with protein. As described above, the thermic effect of protein is high. Greater protein intake on the keto diet is more energetically costly. In addition, when carb intake is very low, protein is used to make glucose via a process called gluconeogenesis. The energy cost for this is estimated to be ~ 400 to 600 calories/day.12 
  2. Increased ability to burn fat. Keto-adaptation more than doubles the rate of fat burning compared to a high-carb diet.13 In addition, lower levels of insulin trigger fat burning, reduce fat storage, and increase lean mass.4,5 

Published studies have established that a metabolic advantage of low-carb diets can occur.4,3,14 A recent pilot study - though flawed and biased against low-carb eating - showed a significant increase in energy expenditure (100-150 calories/day) associated with a ketogenic diet (Hall2016). If sustained, this would lead to ~ 10 to 15 pounds of fat lost, or not gained, over a year.

Appetite Suppression

A very common symptom of the ketogenic diet is appetite suppression.15 Feeling more full and satisfied and less hungry may be linked to higher intake of protein and fat. The state of nutritional ketosis also contributes to reduced appetite via two mechanisms. Ketosis suppresses ghrelin - a hormone that increases hunger,16 while high levels of the ketone beta-hydroxybutyrate may act directly as a satiety signal.17 Exogenous ketosis induced by HVMN Ketone - a ketone ester drink - also decreases appetite and ghrelin.18 

Image of person holding their hungry demonstrating lack of appetite

While both appetite suppression and higher energy expenditure likely play a role in low-carb weight loss, they may not always act independently. For example, the increase in body temperature resulting from the greater energy cost of higher protein consumption translates into feelings of satiety (Westerterp2004) (Feinman2007).

Now....let’s return to the main question at it necessary to track calories on keto?

Calorie counting and keto: summary and conclusion

The debate about whether or not to focus on calorie counting for weight loss rages on. Yes, calories certainly matter. But is it necessary to track them?

Counting calories is obviously important for anyone trying to adhere to a calorie-controlled diet for weight loss. However, cutting calories (and thus tracking them) is ineffective for long-term weight reduction.The body defends its body weight by slowing metabolism19 and increasing hunger. The underlying metabolic issues such as insulin resistance have not been resolved. They persist. This failed traditional approach of calorie deprivation has been used for decades while obesity rates continue to soar. The vast majority of overweight people are unable to lose much weight and keep it off.20 

Strict control of calorie balance is especially unnecessary on the ketogenic diet. The keto diet is consistent with the foods we were designed to eat. A diet low in starchy/sugary carbs and favoring proteins and fats, along with fiber-rich vegetables, was the mainstay for humans for thousands of years. Satiating proteins and fats promote satiety and help control blood sugar to reduce cravings. Resting metabolic rate increases somewhat, and does not continue to spiral downward as the body sheds excess fat. As you become more fat- and keto-adapted, you burn calories at a higher clip. Furthermore, elevated levels of ketones (beta-hydroxybutyrate) reduce inflammation.21 

Thus, body weight is self-regulated on the keto diet. No real need to track calories. The keto diet emphasizes the types of food over quantity of food consumed. This is the best approach to reducing obesity, as well as related disorders such as diabetes and cardiovascular diseases.22 

Nevertheless, counting calories on keto may be useful for people who are not getting results. These individuals may be unknowingly consuming too many fats such as coconut oil, for example, in order to increase ketones. Tracking calories may help them get a reality check on what normal portion sizes look like.

  1. Johnston, C. S., Day, C. S., & Swan, P. D. (2002). Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. J Am Coll Nutr, 21(1), 55-61.

  2. Ebbeling, C. B., Swain, J. F., Feldman, H. A., Wong, W. W., Hachey, D. L., Garcia-Lago, E., & Ludwig, D. S. (2012). Effects of dietary composition on energy expenditure during weight-loss maintenance. Jama, 307(24), 2627-2634.

  3. Feinman, R. D., & Fine, E. J. (2004). "A calorie is a calorie" violates the second law of thermodynamics. Nutr J, 3, 9.

  4. Feinman, R. D., & Fine, E. J. (2007). Nonequilibrium thermodynamics and energy efficiency in weight loss diets. Theor Biol Med Model, 4, 27.

  5. Volek, J.S., Sharman, M.J., Love, D.M., Avery, N.G., Gomez, A.L., Scheett, T.P., and Kraemer, W.J. (2002). Body composition and hormonal responses to a carbohydrate-restricted diet. Metabolism 51.

  6. Evero, N., Hackett, L. C., Clark, R. D., Phelan, S., & Hagobian, T. A. (2012). Aerobic exercise reduces neuronal responses in food reward brain regions. J Appl Physiol (1985), 112(9), 1612-1619.

  7. Black, L. E., Swan, P. D., & Alvar, B. A. (2010). Effects of intensity and volume on insulin sensitivity during acute bouts of resistance training. J Strength Cond Res, 24(4), 1109-1116.

  8. Ahren, B., & Thorsson, O. (2003). Increased insulin sensitivity is associated with reduced insulin and glucagon secretion and increased insulin clearance in man. J Clin Endocrinol Metab, 88(3), 1264-1270.

  9. Bueno, N. B., de Melo, I. S., 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. Br J Nutr, 110(7), 1178-1187.

  10. Hallberg, S. J., McKenzie, A. L., Williams, P. T., Bhanpuri, N. H., Peters, A. L., Campbell, W. W., . . . Volek, J. S. (2018). Effectiveness and Safety of a Novel Care Model for the Management of Type 2 Diabetes at 1 Year: An Open-Label, Non-Randomized, Controlled Study. Diabetes Ther.

  11. Willi, S. M., Oexmann, M. J., Wright, N. M., Collop, N. A., & Key, L. L., Jr. (1998). The effects of a high-protein, low-fat, ketogenic diet on adolescents with morbid obesity: body composition, blood chemistries, and sleep abnormalities. Pediatrics, 101(1 Pt 1), 61-67.

  12. Paoli A, Rubini A, Volek JS, Grimaldi KA. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. European Journal of Clinical Nutrition. 2013;67(8):789-796. doi:10.1038/ejcn.2013.116.

  13. Volek, J.S., Freidenreich, D.J., Saenz, C., Kunces, L.J., Creighton, B.C., Bartley, J.M., Davitt, P.M., Munoz, C.X., Anderson, J.M., Maresh, C.M., et al. (2016). Metabolic characteristics of keto-adapted ultra-endurance runners. Metabolism 65, 100-110.

  14. Manninen AH. Metabolic Effects of the Very-Low-Carbohydrate Diets: Misunderstood “Villains” of Human Metabolism. Journal of the International Society of Sports Nutrition. 2004;1(2):7-11. doi:10.1186/1550-2783-1-2-7.

  15. Gibson, A.A., Seimon, R.V., Lee, C.M., Ayre, J., Franklin, J., Markovic, T.P., Caterson, I.D., and Sainsbury, A. (2015). Do ketogenic diets really suppress appetite? A systematic review and meta-analysis. Obes. Rev. 16, 64-76.

  16. Sumithran, P., Prendergast, L. A., Delbridge, E., Purcell, K., Shulkes, A., Kriketos, A., & Proietto, J. (2013). Ketosis and appetite-mediating nutrients and hormones after weight loss. Eur J Clin Nutr, 67(7), 759-764.

  17. Johnstone, A. M., Horgan, G. W., Murison, S. D., Bremner, D. M., & Lobley, G. E. (2008). Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum. Am J Clin Nutr, 87(1), 44-55.

  18. Stubbs BJ, Cox PJ, Evans RD, Cyranka M, Clarke K, De wet H. A Ketone Ester Drink Lowers Human Ghrelin and Appetite. Obesity (Silver Spring). 2018;26(2):269-273.

  19. Martin, C. K., Heilbronn, L. K., de Jonge, L., DeLany, J. P., Volaufova, J., Anton, S. D., . . . Ravussin, E. (2007). Effect of calorie restriction on resting metabolic rate and spontaneous physical activity. Obesity (Silver Spring), 15(12), 2964-2973.

  20. Kraschnewski, J. L., Boan, J., Esposito, J., Sherwood, N. E., Lehman, E. B., Kephart, D. K., & Sciamanna, C. N. (2010). Long-term weight loss maintenance in the United States. Int J Obes (Lond), 34(11), 1644-1654.

  21. Youm, Y.-H., Nguyen, K.Y., Grant, R.W., Goldberg, E.L., Bodogai, M., Kim, D., D'Agostino, D., Planavsky, N., Lupfer, C., Kanneganti, T.D., et al. (2015). The ketone metabolite [beta]-hydroxybutyrate blocks NLRP3 inflammasome-mediated inflammatory disease. Nat. Med. 21, 263-269.

  22. Malhotra, A., DiNicolantonio, J. J., & Capewell, S. (2015). It is time to stop counting calories, and time instead to promote dietary changes that substantially and rapidly reduce cardiovascular morbidity and mortality. Open Heart, 2(1), e000273.

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