The Pareto Principle
The 80/20 diet is based on the Pareto Principle, an economic rule stating that 80% of consequences (or outputs) come from 20% of causes (inputs). It suggests eating nutritious foods for 80% of the time and relaxing on the remaining 20%. This way of eating is not a diet plan, but rather a mindset and is open to individual interpretation. The point of the principle is to recognise that most things in life are not distributed evenly.
The Pareto Principle applied to many other facets of life as well making it a well-known phenomenon. For example, research has shown that 20% of books account for 80% of all library lending. The founder of the principle was Italian economist Vilfredo Pareto in 1906. 20% of Italians held 80% of the nation’s wealth. Applying this to an eating plan is one way to achieve good nutrition without depriving oneself of eating joyfully. Wikipedia defines this principle as follows: “The Pareto principle states that for many outcomes, roughly 80% of consequences come from 20% of causes. In 1941, management consultant Joseph M. Juran developed the concept in the context of quality control and improvement after reading the works of Italian sociologist and economist Vilfredo Pareto, who wrote in 1906 about the 80/20 connection while teaching at the University of Lausanne. In his first work, Pareto showed that approximately 80% of the land in the Kingdom of Italy was owned by 20% of the population. The Pareto principle is only tangentially related to the Pareto efficiency.
The link between the Pareto Principle and eating habits/plans/diets has been published in “The 80/20 Pareto Diet: The magical power of intermittent fasting for a slim body and a smart mind” by David De Angelis (2019) (self-published by the author). This book claims to present a model of "intermittent fasting" representing an "ancient secret", but rediscovered by itself in modern times and always supported by more scientific research to support its validity and effectiveness, not only in terms of weight (fat mass) ), but also in terms of longevity and physical and mental well-being. The “ancient secret” being the Pareto Principle, which had absolutely nothing to do with an eating plan. The book claims “Simple principles, great results! And supported by numerous scientific studies!
I cannot find any scientific studies to support the Pareto Principle 80:20 of eating. If the author claims that the 80/20 Pareto Diet is in fact just intermittent fasting (one day out of 5 each week where you drastically reduce calorie intake), then the evidence even for that is not great. In an Annual Review of Nutrition paper (Patterson and Sears 2017) the conclusion was that “Modified fasting regimens appear to promote weight loss and may improve metabolic health. Several lines of evidence also support the hypothesis that eating patterns that reduce or eliminate nighttime eating and prolong nightly fasting intervals may result in sustained improvements in human health” This is not really convincing evidence when the words “appear to promote weight loss” and “may improve metabolic health” are used, much like the supportive information on individual vitamins, minerals and fat-loss supplements. To date, only three long-term (1 year) trials have evaluated Intermittent Fasting (IMF) as a weight loss strategy, where none of the studies showed significant differences between IMF and Daily Caloric Restriction (DCR) in weight loss (Trepanowski et al. 2017; Carter et al. 2018; Headland et al. 2019). It should be noted that each of these studies had limitations, which prohibited drawing generalizable conclusions about the relative long-term efficacy of IMF compared to DCR for obesity (Ostendorf et al. 2022).
The link between the two is completely fictitious, and there is no supportive data to suggest that this planned method of eating is healthy and/or useful in people losing body fat. The two days a week of restrictive calorie consumption (2 and 7) comes somewhat close and most eating plans allow for one “cheat” day a week where you don’t strictly adhere to healthy eating and/or restricting calories, which is 14% of the week – this is because your body starts to slow its metabolic rate under a regime where daily calorie intake is not sufficient to sustain all your body’s repair, growth and maintenance including exercise calorie output, so as a consequence it will start to draw upon stores of body fat as a fuel – that is the general philosophy. So by having a so called cheat day your body is not in a continual downward spiral of a slowing metabolic rate. Your body always wants to maintain where it is at and doesn’t intuitively know that you are “overweight” or “obese”. A recent publication by van Galen et al. (2023) showed alarmingly that obese patients have severely impaired brain responses after ingesting food and that this impaired neural response is not restored after diet-induced weight loss. This impaired neural responses most likely contributes to overeating and ongoing resistance to nutrient signals after eating. This may explain the high rate of weight regain after successful weight loss due to calorie restriction. This highlights the need to increase activity and exercise as a method of weight loss by comparison with calorie restriction.
References
Carter S, Clifton PM, Keogh JB (2018) Effect of intermittent compared with continuous energy restricted diet on glycemic control in patients with type 2 diabetes: a randomized noninferiority trial. JAMA Network Open 1(3), e180756.
De Angelis, D (2019) The 80/20 Pareto Diet: The magical power of intermittent fasting for a slim body and a smart mind.
Headland ML, Clifton PM, Keogh JB. (2019) Effect of intermittent compared to continuous energy restriction on weight loss and weight maintenance after 12 months in healthy overweight or obese adults. International Journal of Obesity 43(10):2028–36.
Ostendorf, DM, Caldwell, AE, Zaman, A. et al. (2022) Comparison of weight loss induced by daily caloric restriction versus intermittent fasting (DRIFT) in individuals with obesity: study protocol for a 52-week randomized clinical trial. Trials 23, 718. https://doi.org/10.1186/s13063-022-06523-2
Patterson, RE and Sears, DD (2017) Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition 37, https://doi.org/10.1146/annurev-nutr-071816-064634
Trepanowski JF, Kroeger CM, Barnosky A, et al. (2017) Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults: A randomized clinical trial. JAMA Intern Med. 177(7), 930–8. https:// doi. org/ 10. 1001/ jamai nternmed. 2017. 0936.
van Galen, K.A., Schrantee, A., ter Horst, K.W. et al. (2023) Brain responses to nutrients are severely impaired and not reversed by weight loss in humans with obesity: a randomized crossover study. Nature Metabolism, 5, 1059–1072. https://doi.org/10.1038/s42255-023-00816-9
Dr David Cook
Senior Research Scientist
Get up to Move.
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