{"id":516431,"date":"2025-10-21T07:30:21","date_gmt":"2025-10-21T07:30:21","guid":{"rendered":"https:\/\/www.europesays.com\/uk\/516431\/"},"modified":"2025-10-21T07:30:21","modified_gmt":"2025-10-21T07:30:21","slug":"whats-the-cap-on-human-energy-expenditure-elite-athletes-reveal-metabolic-ceiling","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/uk\/516431\/","title":{"rendered":"What\u2019s the cap on human energy expenditure? Elite athletes reveal \u2018metabolic ceiling\u2019"},"content":{"rendered":"<p> <img decoding=\"async\" class=\"figure__image\" alt=\"Competitors race over a sand dune during a marathon in the southern Moroccan Sahara desert.\" loading=\"lazy\" src=\"https:\/\/www.europesays.com\/uk\/wp-content\/uploads\/2025\/10\/d41586-025-03389-7_51582330.jpg\"\/><\/p>\n<p class=\"figure__caption u-sans-serif\">Ultra-runners face a limit on how much energy they can expend.Credit: Jean-Philippe Ksiazek\/AFP via Getty<\/p>\n<p>The human body has a \u2018metabolic ceiling\u2019 that even the most extreme athletes cannot surpass. A study<a href=\"#ref-CR1\" data-track=\"click\" data-action=\"anchor-link\" data-track-label=\"go to reference\" data-track-category=\"references\">1<\/a> published today in the journal Current Biology finds that over a prolonged period \u2014 of 30 weeks or more \u2014 that ceiling is about 2.4 times an athlete\u2019s basal metabolic rate (BMR), the minimum amount of energy the body needs per day for essential tasks, such as breathing.<\/p>\n<p>For short periods, people can burn up to about ten times their BMR. Researchers have previously proposed that the body has a metabolic limit<a href=\"#ref-CR2\" data-track=\"click\" data-action=\"anchor-link\" data-track-label=\"go to reference\" data-track-category=\"references\">2<\/a> of around 2.5 times BMR over extended periods, but it has never been properly tested until now, says Andrew Best, a biological anthropologist at Massachusetts College of Liberal Arts in North Adams and a co-author of the work.<\/p>\n<p>Best and his colleagues recruited 14 high-endurance athletes \u2014 ultra-runners, cyclists and triathletes. Participants drank doubly labelled water containing deuterium and oxygen-18, which are heavy isotopes of hydrogen and oxygen. Once ingested, both deuterium and oxygen-18 will be lost from the body in the form of water, through urine and sweat. However, some of the oxygen-18 will also exit the body in the form of exhaled carbon dioxide.<\/p>\n<p>By tracing the quantity of these molecules that were flushed out in urine, the scientists were able to calculate the amount of CO2 exhaled, and, from this, estimate the number of calories the athletes burnt. This allowed the team to trace the athletes\u2019 energy output as they did activities \u2014 such as competitions \u2014 in real time, rather than measuring them on treadmills in a laboratory, says Best. <\/p>\n<p>Hitting the ceiling<\/p>\n<p>During multi-day competitions, some athletes burnt around 9,000 calories a day. But over longer periods \u2014 30 and 52 weeks \u2014 their energy expenditure averaged about 2.4 times their BMR. The results show that even the most extreme athletes reach a metabolic ceiling that it is exceptionally difficult to exceed.<\/p>\n<p>The researchers also found that when athletes devoted more energy to running, cycling and swimming, they unconsciously cut back on using energy elsewhere, such as walking or fidgeting.<\/p>\n","protected":false},"excerpt":{"rendered":"Ultra-runners face a limit on how much energy they can expend.Credit: Jean-Philippe Ksiazek\/AFP via Getty The human body&hellip;\n","protected":false},"author":2,"featured_media":516432,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[35,3965,1549,3966,445,70,16,15],"class_list":{"0":"post-516431","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-energy","9":"tag-humanities-and-social-sciences","10":"tag-metabolism","11":"tag-multidisciplinary","12":"tag-obesity","13":"tag-science","14":"tag-uk","15":"tag-united-kingdom"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@uk\/115410988867090401","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/516431","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/comments?post=516431"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/516431\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media\/516432"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media?parent=516431"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/categories?post=516431"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/tags?post=516431"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}