In an age where all nutritional information is just one click away, we find people who tell you how fattening food is while they drink their coffee with a chunk of butter.  It is not unusual to hear claims like: “Carbs are the problem”, “Insulin is responsible for your being fat” or “Calories don´t matter if you do a ketogenic diet”.Before presenting why all these claims are incorrect, I would like to emphasize that I have nothing against low carb diets and that even I use them as a tool for many of my athletes when I am after improving body composition, however, the reason is not due to a ‘metabolic advantage’ with other diets, but much more simple reasons.

Creating a caloric deficit

Many people who argue against the CICO theory fall into the trap of believing that we are dealing with a static system, when we are actually talking about a dynamic in which our body varies its response according to the caloric intake. In other words, the amount of calories we ingest affect the amount of calories we expend. It has been shown in several studies (1-6) that when we increase the caloric intake (and thus increasing body weight) it can lead to increases in the total daily energy expenditure (TDEE), while when we cut down our caloric intake, we are reducing the amount of calories we burn in a day. In this way, we will see that de actual long term weight loss will be inferior than expected (7) regardless of whether we are on a low or high carb diet. Even so, we have to take into account that the person’s behavior will influence more their weight loss results than the metabolic adaptations.

When we consider the dieter’s behavior, we can observe that most of them underestimate their intake or overestimate their expenditure (8-13), even though they know that the researchers themselves are watching them (14). On the other hand, we find that when the person know the amount of calories he or she has expended, they feel freer to ingest palatable foods. (15). Considering that nowadays, most people use wearable devices that overestimate expenditure during training (16), the difference between reported calories vs actual caloric intake is even larger. This is one of the reasons why we find inconsistencies when we compare low carb vs low fat diets in conditions where subjects are free to do what they want.

Another limitation is that many of the studies used at favoring low carb diets have a superior protein intake, consequently we wouldn’t be speaking about high carb diets vs high fat diets, but about high protein diets vs low protein diets. This is a major factor since when we increase protein we lose less fat free tissue, our appetite is reduced and even (in a modest way) we increase TDEE (17-23).

So, what happens when we control the calorie and protein amount in both diets?

When we review the studies in which both parameters are controlled for, we see there are no significant differences. Golay et al (24, 25) reported that when protein and caloric intake were identical during a severe caloric deficit, there was no difference in fat loss between having 15% or 45% of the total energy intake in the form of carbohydrates. Hall et al (26) reached the same conclusion in their study, where they reported no difference in fat loss between a ketogenic diet and a moderate carbohydrate diet when calories and proteins where matched. Further, a meta-analysis performed by Johnston  et al (27) concluded that the difference between both diets had a minor difference of only 0.2kg (0.44lb) for a whole year.

Adapted from Hall et al (2016).

Adapted from Johnson et al (2014).

And here is where the real problem is: Every diet fails in the long term if there is no adherence.  

Regardless of the diet’s carbohydrate intake, we see that in the period from 6 months to a year is when most people regain part of the lost weight (metabolic adaptations, lack of adherence to the diet, more hunger…) Thus, blaming carbs as the only cause for obesity makes no sense at all.

On the other hand, is there evidence that you can loss a lot of weight while consuming a very high carbohydrate diet .The answer is yes!

For that we have to call upon the 40’s, when Walter Kempner’s diet known as ‘the rice diet’ made the spotlight. This diet is based exclusively on rice, vegetables and fruit, which made the carbohydrate intake over 90%. Leaving aside the fact that we´re not talking about an ‘optimal’ diet due to the lack of protein and fat intake, it really helps us understand how carb intakes over 500g, could make someone lose more than 45kg (99lb) of body weight (reaching over 100kg (220lb) in some guy) if they are in a caloric deficit (28).


Subjects from Walter Kempner’s study.

Currently, we have populations like the Kitavas or the Okinawas where the carbohydrate intake is reported to be over 70 and 90% of their  total caloric intake respectively and somehow, they don’t exhibit obesity nor 21st century diseases because their caloric intake isn’t high (29-35). It would be expected  that within a framework where the caloric intake (mainly carbs) is very high, our body would shift from the usage of fatty acids to carbs as a main source of energy. This fact will make no time for the ingested fat to oxidize completely and therefore be stored in the form of triglycerides and fat tissue. Thus, we can say that whenever we speak about caloric surplus, the dietary fat storage will be more effective than the carb surplus and therefore, lipogenesis would not occur easily again, at least in humans.

At the end of the day, it is energy balance that determines fat loss to a greater or lesser extent and not if you are following a high or a low carbohydrate diet. Adherence to the diet is an important cornerstone if we want to achieve long term fat loss and to accomplish this, we have to educate people making them see that whether they follow a high carbohydrate diet or a high fat diet, you can achieve your goals as long as you are in a caloric deficit and you find a diet that is sustainable for you in the long run.


1. Foster GD, Wadden TA, Kendrick ZV, Letizia KA, Lander DP, Conill AM. The energy cost of walking before and after significant weight loss. Med Sci Sports Exerc. 1995 Jun;27(6):888-94.

2. R.N. Kulkarni & Shetty, PS. Net mechanical efficiency during stepping in chronically energy-deficient human subjects. Annals of Human Biology Volume 19, 1992 – Issue 4. Pages 421-425

3. Leibel RL, Rosenbaum M, and Hirsch J. Changes in energy expenditure resulting from altered body weight. N Engl J Med 332: 621–628, 1995.

4. Levine JA, Eberhardy NL, and Jensen MD. Role of nonex- ercise activity thermogenesis in resistance to fat gain in humans. Science 283: 212–214, 1999.

5 Müller MJ1, Geisler C1. From the past to future: from energy expenditure to energy intake to energy expenditure. Eur J Clin Nutr. 2017 Mar;71(3):358-364

6. Rosenbaum M1, Vandenborne K, Goldsmith R, Simoneau JA, Heymsfield S, Joanisse DR, Hirsch J, Murphy E, Matthews D, Segal KR, Leibel RL. Effects of experimental weight perturbation on skeletal muscle work efficiency in human subjects. Am J Physiol Regul Integr Comp Physiol. 2003 Jul;285(1):R183-92.

7. Thomas DM1, Martin CK, Lettieri S, Bredlau C, Kaiser K, Church T, Bouchard C, Heymsfield SB.. Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule.

8. J H de Vries, P L Zock, R P Mensink, and M B Katan. Underestimation of energy intake by 3-d records compared with energy intake to maintain body weight in 269 nonobese adults.

9. Hirvonen T1, Männistö S, Roos E, Pietinen P. Increasing prevalence of underreporting does not necessarily distort dietary surveys. Eur J Clin Nutr. 1997 May;51(5):297-301.

10. Scagliusi FB1, Polacow VO, Artioli GG, Benatti FB, Lancha AH Jr. Selective underreporting of energy intake in women: magnitude, determinants, and effect of training. J Am Diet Assoc. 2003 Oct;103(10):1306-13.

11. Barbara C. Olendzki, RD MPH, Yunsheng Ma, MD, PhD, James R. Hebert, MSPH, ScD, Sherry Pagoto, PhD, Philip Merriam, MSPH, Milagros Rosal, PhD, and Ira S. Ockene, MD. Underreporting of energy intake and associated factors in a Latino population at risk of developing type 2 diabetes. J Am Diet Assoc. 2008 Jun; 108(6): 1003–1008.

12. Rennie KL1, Coward A, Jebb SA. Estimating under-reporting of energy intake in dietary surveys using an individualised method. Br J Nutr. 2007 Jun;97(6):1169-76

13. Lichtman SW1, Pisarska K, Berman ER, Pestone M, Dowling H, Offenbacher E, Weisel H, Heshka S, Matthews DE, Heymsfield SB. Discrepancy between self-reported and actual caloric intake and exercise in obese subjects. N Engl J Med. 1992 Dec 31;327(27):1893-8.

14. Muhlheim LS1, Allison DB, Heshka S, Heymsfield SB. Do unsuccessful dieters intentionally underreport food intake? Int J Eat Disord. 1998 Nov;24(3):259-66

15. McCaig DC, Hawkins LA1, Rogers PJ. Licence to eat: Information on energy expended during exercise affects subsequent energy intake. Appetite. 2016 Dec 1;107:323-329.

16. Nelson MB1, Kaminsky LA, Dickin DC, Montoye AH. Validity of Consumer-Based Physical Activity Monitors for Specific Activity Types. Med Sci Sports Exerc. 2016 Aug;48(8):1619-28

17. Pasiakos SM1, Cao JJ, Margolis LM, Sauter ER, Whigham LD, McClung JP, Rood JC, Carbone JW, Combs GF Jr, Young AJ. Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial. FASEB J. 2013 Sep;27(9):3837-47

18. John W. Apolzan,Nadine S. Carnell,3 Richard D. Mattes, and Wayne W. Campbell. Inadequate Dietary Protein Increases Hunger and Desire to Eat in Younger and Older Men

19. Hall WL1, Millward DJ, Long SJ, Morgan LM. Casein and whey exert different effects on plasma amino acid profiles, gastrointestinal hormone secretion and appetite. Br J Nutr. 2003 Feb;89(2):239-48.

20. Hochstenbach-Waelen A1, Veldhorst MA, Nieuwenhuizen AG, Westerterp-Plantenga MS, Westerterp KR. Comparison of 2 diets with either 25% or 10% of energy as casein on energy expenditure, substrate balance, and appetite profile

21. Paddon-Jones D1, Westman E, Mattes RD, Wolfe RR, Astrup A, Westerterp-Plantenga M. Protein, weight management, and satiety. Am J Clin Nutr. 2008 May;87(5):1558S-1561S

22. Leidy HJ, Carnell NS, Mattes RD, Campbell WW. Higher protein intake preserves lean mass and satiety with weight loss in pre-obese and obese women. Obesity (Silver Spring). 2007 Feb;15(2):421-9.

23. Jaapna Dhillon et al. The Effects of Increased Protein Intake on Fullness: A Meta-Analysis and Its Limitations. Journal of the academy of nutrition and dietetics June 2016Volume 116, Issue 6, Pages 968–983

24. Golay A1, Allaz AF, Morel Y, de Tonnac N, Tankova S, Reaven G. Similar weight loss with low- or high-carbohydrate diets. Am J Clin Nutr. 1996 Feb;63(2):174-8.

25. Golay A1, Eigenheer C, Morel Y, Kujawski P, Lehmann T, de Tonnac N. Weight-loss with low or high carbohydrate diet? Int J Obes Relat Metab Disord. 1996 Dec;20(12):1067-72.

26. Kevin D Hall,3* Kong Y Chen,3 Juen Guo,3 Yan Y Lam,4 Rudolph L Leibel,5 Laurel ES Mayer,5 Marc L Reitman,3 Michael Rosenbaum,5 Steven R Smith,6 B Timothy Walsh,5 and Eric RavussinEnergy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men. AJCN. July 6, 2016

27. Johnston BC, Kanters S, Bandayrel K, Wu P, Naji F, Siemieniuk RA, Ball GD, Busse JW, Thorlund K, Guyatt G1, Jansen JP, Mills EJ. Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA. 2014 Sep 3;312(9):923-33

28. Walter Kempner, MD; Barbara C. Newborg, MD; Ruth L. Peschel, MD; et al. Treatment of Massive Obesity With Rice/Reduction Diet Program An Analysis of 106 Patients With at Least a 45-kg Weight Loss. Arch Intern Med. 1975;135(12):1575-1584

29. Lindeberg S1, Nilsson-Ehle P, Terént A, Vessby B, Scherstén B. Cardiovascular risk factors in a Melanesian population apparently free from stroke and ischaemic heart disease: the Kitava study. J Intern Med. 1994 Sep;236(3):331-40.

30. Lindeberg S1, Eliasson M, Lindahl B, Ahrén B. Low serum insulin in traditional Pacific Islanders–the Kitava Study. Metabolism. 1999 Oct;48(10):1216-9.

31. Lindeberg S1, Lundh B. Apparent absence of stroke and ischaemic heart disease in a traditional Melanesian island: a clinical study in Kitava. J Intern Med. 1993 Mar;233(3):269-75.

32. Lindeberg S1, Berntorp E, Nilsson-Ehle P, Terént A, Vessby B. Age relations of cardiovascular risk factors in a traditional Melanesian society: the Kitava Study. Am J Clin Nutr. 1997 Oct;66(4):845-52.

33. Cockerham WC1, Yamori Y. Okinawa: an exception to the social gradient of life expectancy in Japan. Asia Pac J Clin Nutr. 2001;10(2):154-8

34. Willcox BJ1, Willcox DC, Todoriki H, Fujiyoshi A, Yano K, He Q, Curb JD, Suzuki M. Caloric restriction, the traditional Okinawan diet, and healthy aging: the diet of the world’s longest-lived people and its potential impact on morbidity and life span. Ann N Y Acad Sci. 2007 Oct;1114:434-55.

35. Natalia S. Gavrilova and Leonid A. Gavrilov. Comments on Dietary Restriction, Okinawa Diet and Longevity. Gerontology. 2012 Apr; 58(3): 221–223