'''ケトーシス'''({{lang-en-short|ketosis}})には、[[生理的ケトーシス]]と病理的ケトーシスがある。'''ケトーシス'''({{lang-en-short|ketosis}})は、[[ケトン体]]([[3-ヒドロキシ酪酸]])が増加することである。[[ケトン体]]は空腹時や運動時に増加する<ref>Puchalska P, Crawford PA. Multi-dimensional Roles of Ketone Bodies in Fuel Metabolism, Signaling, and Therapeutics. Cell Metab. 2017 Feb 7;25(2):262-284. {{doi|10.1016/j.cmet.2016.12.022}}. {{PMID|28178565}}; {{PMCID|5313038}}.</ref><ref> Vidali S, Aminzadeh S, Lambert B, Rutherford T, Sperl W, Kofler B, Feichtinger RG. Mitochondria: The ketogenic diet--A metabolism-based therapy. Int J Biochem Cell Biol. 2015 Jun;63:55-9. {{doi|10.1016/j.biocel.2015.01.022}}. Epub 2015 Feb 7. {{PMID|25666556}}.</ref>。また[[ケトン体]]の健康効果を期待して[[ケトン供与体]]を摂取したりして[[ケトン体]]を増加させることもある。これを[[生理的ケトーシス]]と呼ぶ<ref>Cox PJ, Kirk T, Ashmore T, Willerton K, Evans R, Smith A, Murray AJ, Stubbs B, West J, McLure SW, King MT, Dodd MS, Holloway C, Neubauer S, Drawer S, Veech RL, Griffin JL, Clarke K. Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes. Cell Metab. 2016 Aug 9;24(2):256-68. {{doi|10.1016/j.cmet.2016.07.010}}. Epub 2016 Jul 27. {{PMID|27475046}}.</ref><ref>Soto-Mota A, Vansant H, Evans RD, Clarke K. Safety and tolerability of sustained exogenous ketosis using ketone monoester drinks for 28 days in healthy adults. Regul Toxicol Pharmacol. 2019 Dec;109:104506. {{doi|10.1016/j.yrtph.2019.104506}}. Epub 2019 Oct 23. {{PMID|31655093}}.</ref><ref>Soto-Mota A, Norwitz NG, Clarke K. Why a d-β-hydroxybutyrate monoester? Biochem Soc Trans. 2020 Feb 28;48(1):51-59. {{doi|10.1042/BST20190240}}. {{PMID|32096539}}; {{PMCID|7065286}}. </ref>。最近[[ケトンエステル]]などの有力な[[ケトン供与体]]が開発されているので、ヒトにおける[[生理的ケトーシス]]の研究が蓄積されつつある<ref>Soto-Mota A, Norwitz NG, Clarke K. Why a d-β-hydroxybutyrate monoester? Biochem Soc Trans. 2020 Feb 28;48(1):51-59. {{doi|10.1042/BST20190240}}. {{PMID|32096539}}; {{PMCID|7065286}}.</ref><ref>Myette-Côté É, Caldwell HG, Ainslie PN, Clarke K, Little JP. A ketone monoester drink reduces the glycemic response to an oral glucose challenge in individuals with obesity: a randomized trial. Am J Clin Nutr. 2019 Dec 1;110(6):1491-1501. {{doi|10.1093/ajcn/nqz232}}. {{PMID|31599919}}; {{PMCID|6885474}}.</ref>。また[[ケトンエステル]]などの[[ケトン供与体]]による[[生理的ケトーシス]]においては有害な事象が起こらなかったという報告が多数ある<ref>Soto-Mota A, Vansant H, Evans RD, Clarke K. Safety and tolerability of sustained exogenous ketosis using ketone monoester drinks for 28 days in healthy adults. Regul Toxicol Pharmacol. 2019 Dec;109:104506. {{doi|10.1016/j.yrtph.2019.104506}}. Epub 2019 Oct 23. {{PMID|31655093}}.</ref><ref>Clarke K, Tchabanenko K, Pawlosky R, Carter E, Todd King M, Musa-Veloso K, Ho M, Roberts A, Robertson J, Vanitallie TB, Veech RL. Kinetics, safety and tolerability of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate in healthy adult subjects. Regul Toxicol Pharmacol. 2012 Aug;63(3):401-8. {{doi|10.1016/j.yrtph.2012.04.008}}. Epub 2012 May 3. {{PMID|22561291}}; {{PMCID|3810007}}.</ref>。
獣医領域においては、以下のような病理的ケトーシスが問題となることがある。主に[[乳牛]]において乳量が低下する場合が問題となる<ref>Benedet A, Manuelian CL, Zidi A, Penasa M, De Marchi M. Invited review: β-hydroxybutyrate concentration in blood and milk and its associations with cow performance. Animal. 2019 Aug;13(8):1676-1689. {{doi|10.1017/S175173111900034X}}. Epub 2019 Mar 11. {{PMID|30854998}}.</ref><ref>Ježek J, Cincović MR, Nemec M, Belić B, Djoković R, Klinkon M, Starič J. Beta-hydroxybutyrate in milk as screening test for subclinical ketosis in dairy cows. Pol J Vet Sci. 2017 Sep 26;20(3):507-512. {{doi|10.1515/pjvs-2017-0061}}. {{PMID|29166271}}.</ref>。[[糖質]]および[[脂質]]の代謝障害により、体内の[[ケトン体]]が異常に増量し、臨床症状を示す状態。'''ケトン症'''とも呼ばれる。血中のケトン体が増量した状態を'''ケトン血症'''、尿中のケトン体が増量した状態を'''ケトン尿症'''、乳中のケトン体が増量した状態を'''ケトン乳症'''と呼び区別する。臨床症状を伴わないケトン体の増量はケトーシスとはみなされない。
^Cox PJ, Kirk T, Ashmore T, Willerton K, Evans R, Smith A, Murray AJ, Stubbs B, West J, McLure SW, King MT, Dodd MS, Holloway C, Neubauer S, Drawer S, Veech RL, Griffin JL, Clarke K. Nutritional Ketosis Alters Fuel Preference and Thereby Endurance Performance in Athletes. Cell Metab. 2016 Aug 9;24(2):256-68. doi:10.1016/j.cmet.2016.07.010. Epub 2016 Jul 27. PMID27475046.
^Soto-Mota A, Vansant H, Evans RD, Clarke K. Safety and tolerability of sustained exogenous ketosis using ketone monoester drinks for 28 days in healthy adults. Regul Toxicol Pharmacol. 2019 Dec;109:104506. doi:10.1016/j.yrtph.2019.104506. Epub 2019 Oct 23. PMID31655093.
^Myette-Côté É, Caldwell HG, Ainslie PN, Clarke K, Little JP. A ketone monoester drink reduces the glycemic response to an oral glucose challenge in individuals with obesity: a randomized trial. Am J Clin Nutr. 2019 Dec 1;110(6):1491-1501. doi:10.1093/ajcn/nqz232. PMID31599919; PMC6885474.
^Soto-Mota A, Vansant H, Evans RD, Clarke K. Safety and tolerability of sustained exogenous ketosis using ketone monoester drinks for 28 days in healthy adults. Regul Toxicol Pharmacol. 2019 Dec;109:104506. doi:10.1016/j.yrtph.2019.104506. Epub 2019 Oct 23. PMID31655093.
^Clarke K, Tchabanenko K, Pawlosky R, Carter E, Todd King M, Musa-Veloso K, Ho M, Roberts A, Robertson J, Vanitallie TB, Veech RL. Kinetics, safety and tolerability of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate in healthy adult subjects. Regul Toxicol Pharmacol. 2012 Aug;63(3):401-8. doi:10.1016/j.yrtph.2012.04.008. Epub 2012 May 3. PMID22561291; PMC3810007.
^Benedet A, Manuelian CL, Zidi A, Penasa M, De Marchi M. Invited review: β-hydroxybutyrate concentration in blood and milk and its associations with cow performance. Animal. 2019 Aug;13(8):1676-1689. doi:10.1017/S175173111900034X. Epub 2019 Mar 11. PMID30854998.
^Ježek J, Cincović MR, Nemec M, Belić B, Djoković R, Klinkon M, Starič J. Beta-hydroxybutyrate in milk as screening test for subclinical ketosis in dairy cows. Pol J Vet Sci. 2017 Sep 26;20(3):507-512. doi:10.1515/pjvs-2017-0061. PMID29166271.