‘Eating less’ does not help – The science behind why this is terrible advice

Something struck me in my academic studies of energy requirements, and it was that when at first they calculated them way back when before the ‘obesity epidemic’, they were estimated to be at 3000 calories (Nieman, 2018). So now I have to ask, why is it that experts and non-experts alike believe in calorie restriction? Why is this a problem only now, and not a hundred years ago? Not that I personally think there is anything morally wrong with taking space or that health cannot be achieved at any weight, but if this is something a client asks me about, how much benefit does calorie restriction offer, and what are the risks involved? If we think this is “good for them”, why is it good, and can this good be achieved otherwise?

There are unfortunately not many new studies that measure the long term effects of dieting. A book with a great first chapter on metabolism explains really well, with the help of overeating and undereating studies from the last century, why our metabolism is so adaptive resilient to weight change (Andrew Jenkinson, 2020). Using the calories in-calories out framework, the weight loss surgeon who wrote the book does the math and shows that if this were true in that simple form, the average American would have gained 26 kg over a year, instead of the observed 6kg in the 80s. Jenkinson (2020) goes into the theory that homeostatic feedback loops complicate this equation to make it harder to lose weight, and Memon et al. (2020) see “hormonal disturbances, interactions with the gut microbiome, lack of sleep, and socioeconomic status” as additional confounders, making calorie restrictive diets an illogical solution.

Old studies cited by Jenkinson (2020) have found that long-term under-eating causes excess weight regain and, similar to the review of (Memon et al., 2020), drastic changes the basal metabolic rate and body composition, and also changes the mechanisms of appetite. On body composition, calorie restriction has been found in one study not to cause changes in abdominal adiposity (Redman & Ravussin, 2011), which interesting, because usually this is the specific type of body adiposity that is associated with disease.

So I am still asking, is restricting calories and losing some fat “good for us”? The study by Redman and Ravussin (2011) mentions how thyroid hormones are affected for the worse on such an intervention, yet applaud in the short term follow-up of 6 months that their subjects report improved eating disorder behaviors, mostly the ones associated with overeating. Why I find this disturbing is because they also state “After 6 months, CR participants reported an increased desire to eat and a decreased satisfaction of appetite.”(Redman & Ravussin, 2011). Who wants to live like that, without exhibiting the behaviors and actions associated with disordered eating, but still have a constant desire to eat and disordered appetite? Is that really sustainable long-term? This is also disturbing because hypothyroid patients are often encouraged by laymen and  health professionals alike to eat less. The science clearly shows that this is very harmful.

Memon et al. (2020) find that disordered eating is caused by dieting. They cite a very interesting study that found that non-dieters when asked to taste/ rate a food did as was expected, namely ate more to rate a food if they had done so on an empty stomach, but ate less on this test if they had been given a meal beforehand. Dieters however did the exact opposite, and restricted their taste test on empty stomachs, but ate more if they had had a meal before.

In a review on the benefits and risks of weight loss (Ryan, 2005), the author lists cholecystitis as one of the risks and mentions that the risk of osteoporosis is decreased in overweight individuals. “Weight loss was found to have a lower mortality rate in obese people with comorbid conditions but was associated with a higher mortality rate in the healthy obese.”(Memon et al., 2020). To show also that health benefits can occur irrespective of size and changes in weight, a study found that markers of metabolic syndrome were reversed within just one month on a low carb-high fat diet, and even though the participants ate more saturated fatty acids and did not lose any weight, their lipid profile improved (Hyde et al., 2019).

Lastly, I find it important to mention that a study has found that weight discrimination increased mortality by 60%, and that “The effect of weight discrimination on mortality was generally stronger than other forms of discrimination and was comparable to other established risk factors, such as history of smoking and disease burden. … These findings suggest the possibility that the stigma associated with weight is more harmful than actual overweight or obesity itself.”(Sutin et al., 2015). This form of discrimination is observed in doctors, nutritionists, and psychologists (Schvey, 2010).

References

Andrew Jenkinson. (2020). Metabology for beginners. In Why we eat (too much) (pp. 3–30). Penguin Random House.
Hyde, P. N., Sapper, T. N., Crabtree, C. D., LaFountain, R. A., Bowling, M. L., Buga, A., Fell, B., McSwiney, F. T., Dickerson, R. M., Miller, V. J., Scandling, D., Simonetti, O. P., Phinney, S. D., Kraemer, W. J., King, S. A., Krauss, R. M., & Volek, J. S. (2019). Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss. JCI insight, 4(12), e128308. https://doi.org/10.1172/jci.insight.128308

Memon, A. N., Gowda, A. S., Rallabhandi, B., Bidika, E., Fayyaz, H., Salib, M., & Cancarevic, I. (2020). Have our attempts to curb obesity done more harm than good? Cureus, 12(9), e10275. https://doi.org/10.7759/cureus.10275
Nieman, D. (2018). Nutritional Assessment (7th ed.). McGraw-Hill Higher Education (US). https://bookshelf.vitalsource.com/books/9781259169748

Redman, L. M., & Ravussin, E. (2011). Caloric Restriction in Humans: Impact on Physiological, Psychological, and Behavioral Outcomes. Antioxidants & Redox Signaling, 14(2), 275–287. https://doi.org/10.1089/ars.2010.3253
Ryan, D. (2005). Risks and benefits of weight loss: Challenges to obesity research. European Heart Journal Supplements, 7(suppl_L), L27–L31. https://doi.org/10.1093/eurheartj/sui083

Schvey, N. (2010, April 1). Weight bias in health care. Journal of Ethics | American Medical Association. Retrieved April 1, 2022, from https://journalofethics.ama-assn.org/article/weight-bias-health-care/2010-04

Sutin, A. R., Stephan, Y., & Terracciano, A. (2015). Weight Discrimination and Risk of Mortality. Psychological science, 26(11), 1803-1811. https://doi.org/10.1177/0956797615601103