It is widely assumed that the fundamental cause of obesity is an energy imbalance between calories consumed and calories expended (”Calories In, Calories Out”).
According to known laws of physics, however, this century-old obesity paradigm must be fallacious. The relevant physical law in terms of body mass regulation is the Law of Conservation of Mass, not the Law of Conservation of Energy.
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Thus, the key to achieve weight and fat loss is to create an imbalance between the nutrient mass intake and the corresponding mass elimination that results from the excretion of nutrient oxidation (”burning”) end-products (1,2,3,4).
Weight gain will take place as nutrient mass ingestion increases even if associated calories are kept at ”weight-maintenance” level. These notions follow from the Law of Conservation of Mass which states, in the context of oxidation reactions, that the mass of the reactants equals the mass of the products with no mass present in the released heat (”Calories Out”).
Therefore, the accumulation of 1 g of either protein, fat, or carbohydrate increases body mass by exactly 1 g independent of the macronutrient’s energy content (”Calories In”). The oxidation of 1 g of any stored macronutrient, on the other hand, reduces body mass by 1 g as the oxidation products are eliminated with the amount of burned calories being inconsequential.
It follows that weight and fat losses produced by isocaloric (i.e., same calorific value) dietary interventions are dependent on the diet’s macronutrient composition. To understand this assertion, consider a 1,300 kcal low-fat diet with calories distributed as 20% fat, 65% carbohydrate and 15% protein. By Atwater factors, the mass intake is this regimen is about 289g.
In contrast, a similar calculation for a 1,300 kcal low-carbohydrate diet, with calories sorted as 70% fat, 15% carbohydrate and 15% protein, reduces mass ingestion to around 199g. This example is, in fact, the norm and not an exception, as a given level of energy intake always requires substantially less nutrient mass when the energy proportion from fat increases. This a consequence of the high caloric density (kcal/g) of fat in comparison to carbohydrate or protein.
As a result, if the daily mass loss in the two diets is similar, then the low-carbohydrate diet will result in greater weight and fat loss versus the low-fat diet since in the former mass intake is 90g (289g – 199g) smaller than in the latter. Such expectation is independent of the characteristic metabolic effects of each diet (e.g., carbohydrate-induced insulin secretion).
In summary, the key to weight and fat loss is to create negative mass balance, not negative energy balance. A recently proposed mass balance model (MBM; ”Mass In, Mass Out”) describes the temporal evolution of body weight and body composition under a wide variety of feeding experiments, and it provides a highly accurate description of the very best human experimental feeding data.
References
- Manninen AH. Chronic positive mass balance is the actual etiology of obesity: time for a paradigm shift? Available at SSRN: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4084218&fbclid=IwAR2YrRC2QK5-1OyMSZWK8_dcHkcqE6YrXKqtuZtbyKnCUcXERkIq2kZgDR4
- Arencibia-Albite F, Manninen AH. The energy balance theory: an unsatisfactory model of body composition fluctuations. medRxiv 2020.10.27.20220202; doi: https://doi.org/10.1101/2020.10.27.20220202
- Arencibia-Albite F, Manninen AH. The mass balance model perfectly fits both Hall et al. underfeeding data and Horton et al. overfeeding data. medRxiv 2021.02.22.21252026; doi: https://doi.org/10.1101/2021.02.22.21252026
- Arencibia-Albite F. Serious analytical inconsistencies challenge the validity of the energy balance theory. Heliyon. 2020 Jul 10;6(7):e04204. doi: 10.1016/j.heliyon.2020.e04204. Erratum in: Heliyon. 2020 Sep 14;6(9):e04609. PMID: 32685707; PMCID: PMC7355950. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7355950/
By Anssi H. Manninen, Executive Director, MBM Research Group