"Calories in, calories out" and macronutrient intake: the hope, hype, and science of calories

One of the central tenets in obesity prevention and management is caloric restriction. This perspective presents salient features of how calories and energy balance matter, also called the "calories in, calories out" paradigm. Determinants of energy balance and relationships to dietary macronutrient content are reviewed. The rationale and features of the carbohydrate-insulin hypothesis postulate that carbohydrate restriction confers a metabolic advantage. According to this model, a large amount of fat intake is enabled without weight gain. Evidence concerning this possibility is detailed. The relationship and application of the laws of thermodynamics are then clarified with current primary research. Strong data indicate that energy balance is not materially changed during isocaloric substitution of dietary fats for carbohydrates. Results from a number of sources refute both the theory and effectiveness of the carbohydrate-insulin hypothesis. Instead, risk for obesity is primarily determined by total calorie intake.

Keywords: CHO-insulin hypothesis; NuSI; calories in, calories out; energy expenditure; laws of thermodynamics; low-carbohydrate diet; metabolic adaptation; metabolic advantage; obesity; thermic effect of food.

Copyright © 2017 the American Physiological Society.

Similar articles

Raben A, Astrup A. Raben A, et al. Int J Obes Relat Metab Disord. 1996 Mar;20 Suppl 2:S24-30. Int J Obes Relat Metab Disord. 1996. PMID: 8646268 Review. No abstract available.

Ludwig DS, Ebbeling CB. Ludwig DS, et al. JAMA Intern Med. 2018 Aug 1;178(8):1098-1103. doi: 10.1001/jamainternmed.2018.2933. JAMA Intern Med. 2018. PMID: 29971406 Free PMC article. Review.

Prentice AM, Poppitt SD. Prentice AM, et al. Int J Obes Relat Metab Disord. 1996 Mar;20 Suppl 2:S18-23. Int J Obes Relat Metab Disord. 1996. PMID: 8646267 Review. No abstract available.

Swithers SE, Davidson TL. Swithers SE, et al. Physiol Behav. 2005 Dec 15;86(5):669-80. doi: 10.1016/j.physbeh.2005.08.056. Epub 2005 Oct 21. Physiol Behav. 2005. PMID: 16243368

Manco M, Mingrone G. Manco M, et al. Curr Opin Clin Nutr Metab Care. 2005 Jul;8(4):431-9. doi: 10.1097/01.mco.0000172585.09762.8e. Curr Opin Clin Nutr Metab Care. 2005. PMID: 15930970 Review.

Cited by

La Porta CAM, Zapperi S. La Porta CAM, et al. Front Public Health. 2024 Aug 7;12:1421509. doi: 10.3389/fpubh.2024.1421509. eCollection 2024. Front Public Health. 2024. PMID: 39171297 Free PMC article.

Dhokte S, Czaja K. Dhokte S, et al. Nutrients. 2024 Mar 30;16(7):1015. doi: 10.3390/nu16071015. Nutrients. 2024. PMID: 38613048 Free PMC article. Review.

Alexander L, Christensen SM, Richardson L, Ingersoll AB, Burridge K, Golden A, Karjoo S, Cortez D, Shelver M, Bays HE. Alexander L, et al. Obes Pillars. 2022 Jan 10;1:100005. doi: 10.1016/j.obpill.2021.100005. eCollection 2022 Mar. Obes Pillars. 2022. PMID: 38085928 Free PMC article.

Bays HE, Golden A, Tondt J. Bays HE, et al. Obes Pillars. 2022 Aug 10;3:100034. doi: 10.1016/j.obpill.2022.100034. eCollection 2022 Sep. Obes Pillars. 2022. PMID: 37990730 Free PMC article.

Ludwig DS. Ludwig DS. Philos Trans R Soc Lond B Biol Sci. 2023 Oct 23;378(1888):20220211. doi: 10.1098/rstb.2022.0211. Epub 2023 Sep 4. Philos Trans R Soc Lond B Biol Sci. 2023. PMID: 37661740 Free PMC article. Review.