Obesity | Definition, Causes, Health Effects, & Facts

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border-right-sm border-left-sm open"> <div class="drawer d-flex flex-column open"> <div class="left-rail-section-content"> <div class="topic-left-rail-header text-truncate bg-gray-50 position-relative text-right d-flex align-items-center"> <div class="tlr-title px-20 py-15 text-left"> <em class="material-icons text-gray-400 d-lg-none" data-icon="toc"></em> <a class="font-serif font-weight-bold text-black link-blue" href="https://www.britannica.com/science/obesity">obesity</a> </div> <button aria-label="Close" class="js-sections-close-button btn-link btn-sm btn d-lg-none position-absolute top-0 p-10 right-0" > <em class="material-icons font-26" data-icon="close"></em> </button> </div> <div class="section-content pl-10 pr-20 pl-sm-50 pr-sm-60 pl-lg-5 pr-lg-10 pt-10 pt-lg-0 bg-gray-50 clear-catfish-ad"> <div class="toc mb-20"> <div class="font-serif font-14 font-weight-bold mx-15 mb-15 mt-20"> Table of Contents </div> <ul class="list-unstyled my-0" data-level="h1"><li data-target="#ref1"><div class="pl-25"><a class="link-gray-900 w-100" href="/science/obesity">Introduction</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref279330"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/science/obesity#ref279330">Defining obesity</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref279331"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/science/obesity#ref279331">The obesity epidemic</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref279332"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/science/obesity#ref279332">Childhood obesity</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref279333"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/science/obesity/Causes-of-obesity">Causes of obesity</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref279334"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/science/obesity/Causes-of-obesity#ref279334">Health effects of obesity</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li><li data-target="#ref279335"><div class="d-flex align-items-center"><div class="ml-25"></div><a class="w-100 link-gray-900" href="/science/obesity/Treatment-of-obesity">Treatment of obesity</a></div><div class="ml-40 toc-drawer sub-toc-drawer"></div></li></ul> <a class="toc-extra-link link-gray-900" href="https://www.britannica.com/science/obesity/additional-info">References & Edit History</a> <a class="toc-extra-link link-gray-900" href="/facts/obesity">Quick Facts & Related Topics</a> </div> <div class="tlr-media-slider pb-10 mb-30"> <a class="section-header link-gray-900 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They write new content and verify and edit content received from contributors.</div> </a> <div data-popper-arrow></div> </div> <span class="btn btn-link editor-link p-0 qa-byline-link gtm-byline font-12 byline-contributor text-decoration-underline"> The Editors of Encyclopaedia Britannica</span></div> <div class="last-updated font-12 font-serif"> <span class="text-gray-700"> Last Updated: <time datetime="2025-03-10T00:00:00CDT" >Mar 10, 2025</time> •</span> <a class="byline-edit-history" href="https://www.britannica.com/science/obesity/additional-info#history" rel="nofollow">Article History</a> </div></div> </div> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button d-none d-sm-block js-sections-inline-button module-spacing btn d-lg-none"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <div class="d-flex d-sm-none flex-row"> <button class="d-flex d-lg-none btn btn-outline-blue border rounded-sm shadow-sm mobile-toc-button gtm-mobile-toc-inline-button js-sections-inline-button module-spacing"> <em class="material-icons mr-5 ml-n10 my-n5 md-icon" data-icon="toc"></em> Table of Contents </button> <button class="ai-ask-button btn btn-sm border-2 btn-outline-red-400 border-red-400 module-spacing js-inline-ai-ask-button p-10 ml-5"> Ask the Chatbot </button> </div> <div class="js-qf-module qf-module px-40 px-sm-20 py-15 mx-auto module-spacing font-14 bg-gray-50 rounded"> <div class="facts-list mt-10"> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Also called: </dt> <dd>corpulence or fatness</dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> </div> <div class=""> <div class="js-fact mb-10 line-clamp clamp-3"> <dl> <dt>Related Topics: </dt> <dd><a href="/science/nutritional-disease" topicid="422916">nutritional disease</a></dd> <dd><a href="/topic/exercise-physical-fitness" topicid="197976">exercise</a></dd> <dd><a href="/science/pickwickian-syndrome" topicid="459493">pickwickian syndrome</a></dd> <dd><a href="/science/childhood-obesity" topicid="2047337">childhood obesity</a></dd> <dd><a href="/science/central-obesity" topicid="1536830">central obesity</a></dd> </dl> <button class="js-more-btn d-none btn btn-unstyled font-12 bg-gray-50" aria-label="Toggle more/less fact data"> <em class="js-content link-blue">(Show more)</em> </button> </div> <div class="text-center"> <a class="btn btn-sm btn-link p-0" href="/facts/obesity"> See all related content </a> </div> </div> </div> </div><div class="bg-gray-50 p-15 rounded module-spacing recent-news d-flex flex-column float-false"> <div> <h2 class="font-weight-bold font-14 m-0 d-inline"> News <span class="text-gray-600">•</span> </h2> <div class="recent-news-item first-recent-news-item d-inline"> <a class="font-14 gtm-ap-news-link" href="https://www.nia.nih.gov/news/timeframe-8-hour-restricted-eating-irrelevant-weight-loss" rel="nofollow">Timeframe of 8-hour restricted eating irrelevant to weight loss</a> <span class="font-14 text-gray-600"> <span>•</span> Mar. 6, 2025, 9:41 PM ET (National Institute on Aging (.gov)) <button class="btn btn-link d-inline p-0 font-12 js-toggle-recent-news"> <span class="text-gray-500">...</span><span>(Show more)</span> </button> </span> </div> </div> <div class="rest-of-recent-news-items"> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://www.news-medical.net/news/20250306/Study-finds-Pacific-children-struggling-with-micronutrient-intake-and-obesity.aspx" rel="nofollow">Study finds Pacific children struggling with micronutrient intake and obesity</a> <span class="font-14 text-gray-600"> <span>•</span> Mar. 6, 2025, 3:33 AM ET (News-Medical) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://www.news-medical.net/news/20250305/Melatonin-protects-skeletal-muscle-from-damage-caused-by-diabesity.aspx" rel="nofollow">Melatonin protects skeletal muscle from damage caused by "diabesity"</a> <span class="font-14 text-gray-600"> <span>•</span> Mar. 5, 2025, 11:55 PM ET (News-Medical) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://www.reuters.com/business/healthcare-pharmaceuticals/obesity-rates-soaring-globally-monumental-social-failure-study-says-2025-03-03/" rel="nofollow">Obesity rates soaring globally in 'monumental social failure', study says</a> <span class="font-14 text-gray-600"> <span>•</span> Mar. 4, 2025, 12:26 AM ET (Reuters) </span> </div> <div class="recent-news-item mt-5"> <a class="font-14 gtm-ap-news-link" href="https://www.news-medical.net/news/20250227/Artificial-sweeteners-may-reduce-metformine28099s-effectiveness-in-weight-and-glucose-control.aspx" rel="nofollow">Artificial sweeteners may reduce metformin’s effectiveness in weight and glucose control</a> <span class="font-14 text-gray-600"> <span>•</span> Feb. 28, 2025, 6:55 AM ET (News-Medical) </span> </div> <button class="js-toggle-recent-news d-flex btn btn-unstyled font-14 pr-10 rounded-sm mt-10" aria-label="Toggle additional news items"> Show less <em class="material-icons" data-icon="expand_less"></em> </button> </div> </div><span class="marker before-article"></span><section data-level="1" id="ref1"><span class="marker PREMOD1 mod-inline"></span><p class="topic-paragraph"><strong><span id="ref201039"></span>obesity</strong>, excessive accumulation of body fat, usually caused by the <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="consumption" href="https://www.merriam-webster.com/dictionary/consumption" data-type="MW">consumption</a> of more <a href="https://www.britannica.com/science/calorie" class="md-crosslink " data-show-preview="true">calories</a> than the body can use. The excess calories are then stored as fat, or <span id="ref1242719"></span><a href="https://www.britannica.com/science/adipose-tissue" class="md-crosslink " data-show-preview="true">adipose tissue</a>. Overweight, if moderate, is not necessarily obesity, particularly in muscular or large-boned individuals.</p><span class="marker MOD1 mod-inline"></span></section> <span class="marker h2"></span><section data-level="1" id="ref279330"> <h2 class="h1">Defining obesity</h2> <span class="marker PREMOD2 mod-inline"></span><div class="assemblies"><div class="w-100"><figure class="md-assembly m-0 mb-md-0 card card-borderless print-false" data-assembly-id="72928" data-asm-type="image"><div class="md-assembly-wrapper card-media" data-type="image"><a href="https://cdn.britannica.com/30/73630-004-0FFB5466/Height-weight-chart-Body-Mass-Index.jpg" class="gtm-assembly-link position-relative d-flex align-items-center justify-content-center media-overlay-link card-media" data-href="/media/1/423747/72928"><picture><source media="(min-width: 680px)" srcset="https://cdn.britannica.com/30/73630-004-0FFB5466/Height-weight-chart-Body-Mass-Index.jpg"><img src="https://cdn.britannica.com/30/73630-004-0FFB5466/Height-weight-chart-Body-Mass-Index.jpg?w=300" alt="body mass index for adults" data-width="365" data-height="330" loading="eager"></picture><button class="magnifying-glass btn btn-circle position-absolute shadow btn-white top-10 right-10" aria-label="Zoom in"><em class="material-icons link-blue" data-icon="zoom_in"></em></button></a></div><figcaption class="card-body"><div class="md-assembly-caption text-muted font-14 font-serif line-clamp"><span><a class="gtm-assembly-link md-assembly-title font-weight-bold d-inline font-sans-serif mr-5 media-overlay-link" href="https://cdn.britannica.com/30/73630-004-0FFB5466/Height-weight-chart-Body-Mass-Index.jpg" data-href="/media/1/423747/72928">body mass index for adults</a><button class="js-more-btn d-none btn btn-unstyled font-12 bg-white js-content" aria-label="Toggle more/less fact data"><span class="link-blue">(more)</span></button></span></div></figcaption></figure></div></div><p class="topic-paragraph">Obesity was traditionally defined as an increase in body weight that was greater than 20 percent of an individual’s ideal body weight—the weight associated with the lowest risk of death, as determined by certain factors, such as age, height, and gender. Based on these factors, <span id="ref1242720"></span><a href="https://www.britannica.com/science/overweight" class="md-crosslink " data-show-preview="true">overweight</a> could then be defined as a 15–20 percent increase over ideal body weight. However, today the definitions of overweight and obesity are based primarily on measures of height and weight—not <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="morbidity" href="https://www.merriam-webster.com/dictionary/morbidity" data-type="MW">morbidity</a>. These measures are used to calculate a number known as <span id="ref1002706"></span><a href="https://www.britannica.com/science/body-mass-index" class="md-crosslink " data-show-preview="true">body mass index</a> (BMI). This number, which is central to determining whether an individual is clinically defined as obese, parallels fatness but is not a direct measure of body fat. Interpretation of BMI numbers is based on weight status groupings, such as underweight, healthy weight, overweight, and obese, that are adjusted for age and sex. For all adults over age 20, BMI numbers correlate to the same weight status designations; for example, a BMI between 25.0 and 29.9 equates with overweight and 30.0 and above with obesity. <span id="ref1070199"></span>Morbid obesity (also known as extreme, or severe, obesity) is defined as a BMI of 40.0 or higher. (<em>See</em> <a href="https://www.britannica.com/science/nutritional-disease/Alcohol#ref247877" class="md-crosslink " data-show-preview="true">nutritional disease: Diet and chronic disease</a>.)</p><span class="marker MOD2 mod-inline"></span> <div class="feature-block callout"><div class="font-weight-bold"><strong>What do you think?</strong></div><ul><li><div><strong><a href="https://www.britannica.com/procon/obesity-debate" class="md-crosslink " data-show-preview="true">Should Obesity Be Treated as a Disease?</a></strong></div></li></ul><p class="topic-paragraph"><strong>Explore the ProCon debate</strong></p></div> </section> <span class="marker h3"></span><section data-level="1" id="ref279331"> <h2 class="h1">The obesity epidemic</h2> <span class="marker PREMOD3 mod-inline"></span><p class="topic-paragraph">Body weight is influenced by the interaction of multiple factors. There is strong evidence of genetic predisposition to fat accumulation, and obesity tends to run in families. However, the rise in obesity in populations <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="worldwide" href="https://www.britannica.com/dictionary/worldwide" data-type="EB">worldwide</a> since the 1980s has outpaced the rate at which genetic <a href="https://www.britannica.com/science/mutation-genetics" class="md-crosslink " data-show-preview="true">mutations</a> are normally incorporated into populations on a large scale. In addition, growing numbers of persons in parts of the world where obesity was once rare have also gained excessive weight. According to the <a href="https://www.britannica.com/topic/World-Health-Organization" class="md-crosslink " data-show-preview="true">World Health Organization</a> (WHO), which considered global obesity an <span id="ref1242721"></span><a href="https://www.britannica.com/science/epidemic" class="md-crosslink " data-show-preview="true">epidemic</a>, in 2016 more than 1.9 billion adults (age 18 or older) worldwide were overweight and 650 million, representing 13 percent of the world’s adult population, were obese.</p><span class="marker MOD3 mod-inline"></span> <span class="marker PREMOD4 mod-inline"></span><p class="topic-paragraph">The prevalence of overweight and obesity varied across countries, across towns and cities within countries, and across populations of men and women. In <a href="https://www.britannica.com/place/China" class="md-crosslink autoxref " data-show-preview="true">China</a> and Japan, for instance, the obesity rate for men and women was about 5 percent, but in some cities in China it had climbed to nearly 20 percent. In 2005 it was found that more than 70 percent of Mexican women were obese. WHO survey <a class="md-dictionary-link md-dictionary-tt-off eb" data-term="data" href="https://www.britannica.com/dictionary/data" data-type="EB">data</a> released in 2010 revealed that more than half of the people living in countries in the <a href="https://www.britannica.com/place/Pacific-Islands" class="md-crosslink autoxref " data-show-preview="true">Pacific Islands</a> region were overweight, with some 80 percent of women in <a href="https://www.britannica.com/place/American-Samoa" class="md-crosslink autoxref " data-show-preview="true">American Samoa</a> found to be obese.</p><span class="marker MOD4 mod-inline"></span> </section> <span class="marker h4"></span><section data-level="1" id="ref279332"> <h2 class="h1"><span id="ref1225851"></span><a href="https://www.britannica.com/science/childhood-obesity" class="md-crosslink ">Childhood obesity</a></h2> <span class="marker PREMOD5 mod-inline"></span><p class="topic-paragraph">Childhood obesity has become a significant problem in many countries. Overweight <span id="ref1242891"></span><a href="https://www.britannica.com/science/childhood-diseases-and-disorders" class="md-crosslink " data-show-preview="true">children</a> often face stigma and suffer from emotional, psychological, and social problems. Obesity can adversely affect a child’s education and future socioeconomic status. In 2004 an estimated nine million American children over age 6, including teenagers, were overweight, or obese (the terms were typically used interchangeably in describing excess fatness in children). Moreover, in the 1980s and 1990s the prevalence of obesity had more than doubled among children age 2 to 5 (from 5 percent to 10 percent) and age 6 to 11 (from 6 percent to 15 percent). By 2015, 20 percent of children age 6 to 19 were obese in the <a href="https://www.britannica.com/place/United-States" class="md-crosslink autoxref " data-show-preview="true">United States</a>. Further estimates in some rural areas of the country indicated that more than 30 percent of school-age children suffered from obesity. Similar increases were seen in other parts of the world. In the United Kingdom, for example, the prevalence of obesity among children age 2 to 10 had increased from 10 percent in 1995 to 14 percent in 2003, and data from a study conducted there in 2007 indicated that 23 percent of children age 4 to 5 and 32 percent of children age 10 to 11 were overweight or obese. By 2016, WHO data indicated, worldwide some 41 million children age 5 or under were overweight or obese.</p><a class="link-module shadow-sm d-block qa-quiz-module" href="/quiz/a-visit-with-the-word-doctor-medical-vocabulary-quiz" data-link-module-iframe-link=""> <img loading="lazy" src="https://cdn.britannica.com/28/254328-131-8CF54640/Yorkshire-terrier-dressed-as-doctor.jpg" alt="A Yorkshire terrier dressed up as a veterinarian or doctor on a white background. (dogs)" class="rounded-sm mr-15" width="70" /> <div class="line-clamp clamp-5"> <div class="module-title bg-green">Britannica Quiz</div> <div class="font-weight-semi-bold mt-5">A Visit with the Word Doctor: Medical Vocabulary Quiz</div> </div> </a><span class="marker MOD5 mod-inline"></span> <span class="marker PREMOD6 mod-inline"></span><p class="topic-paragraph">In 2005 the American Academy of Pediatrics called obesity “the pediatric <a class="md-dictionary-link md-dictionary-tt-off mw" data-term="epidemic" href="https://www.merriam-webster.com/dictionary/epidemic" data-type="MW">epidemic</a> of the new millennium.” Overweight and obese children were increasingly diagnosed with <a href="https://www.britannica.com/science/hypertension" class="md-crosslink " data-show-preview="true">high blood pressure</a>, elevated <a href="https://www.britannica.com/science/cholesterol" class="md-crosslink " data-show-preview="true">cholesterol</a>, and type II <a href="https://www.britannica.com/science/diabetes-mellitus" class="md-crosslink " data-show-preview="true">diabetes mellitus</a>—conditions once seen almost exclusively in adults. In addition, overweight children experience <a href="https://www.britannica.com/science/fracture-of-bone" class="md-crosslink " data-show-preview="true">broken bones</a> and problems with <a href="https://www.britannica.com/science/joint-skeleton" class="md-crosslink " data-show-preview="true">joints</a> more often than normal-weight children. The long-term consequences of obesity in young people are of great concern to pediatricians and <a href="https://www.britannica.com/topic/public-health" class="md-crosslink autoxref " data-show-preview="true">public health</a> experts, because obese children are at high risk of becoming obese adults. Experts on longevity have concluded that today’s American youth might “live less healthy and possibly even shorter lives than their parents” if the rising prevalence of obesity is left unchecked.</p><span class="marker MOD6 mod-inline"></span> <span class="marker PREMOD7 mod-inline"></span><p class="topic-paragraph"><a class="md-dictionary-link md-dictionary-tt-off eb" data-term="Curbing" href="https://www.britannica.com/dictionary/Curbing" data-type="EB">Curbing</a> the rise in childhood obesity was the aim of the Alliance for a Healthier Generation, a partnership formed in 2005 by the American Heart Association, former U.S. president <a href="https://www.britannica.com/biography/Bill-Clinton" class="md-crosslink autoxref " data-show-preview="true">Bill Clinton</a>, and the children’s television network Nickelodeon. The alliance intended to reach children through a vigorous public awareness campaign. Similar projects followed, including American <a href="https://www.britannica.com/topic/first-lady-United-States-title" class="md-crosslink autoxref " data-show-preview="true">first lady</a> <span id="ref1172792"></span><a href="https://www.britannica.com/biography/Michelle-Obama" class="md-crosslink " data-show-preview="true">Michelle Obama</a>’s Let’s Move! program, launched in 2010, and campaigns against overweight and obesity were made in other countries as well.</p><div class="module-spacing"> <DIV class="marketing-INLINE_SUBSCRIPTION marketing-content" data-marketing-id="INLINE_SUBSCRIPTION"><style> .student-promo-banner-wrapper { container-type: inline-size; margin-bottom: 15px; } @container (min-width: 475px) { .student-promo-banner { flex-direction: row; } .student-promo-banner-img-wrapper { margin-bottom: 0; margin-right: 10px; justify-content: flex-start; } .student-promo-banner-text-wrapper { text-align: left; margin-bottom: 0px; margin-left: 10px; } .student-promo-banner-button-wrapper { margin-right: 0; } }</style> <div class="student-promo-banner-wrapper"> <div class="student-promo-banner d-flex flex-column align-items-center bg-blue rounded p-20"> <div class="student-promo-banner-img-wrapper mb-20 mr-0 d-flex justify-content-center"> <img class="rounded" style="max-width: 100px; min-width: 80px" src="https://cdn.britannica.com/marketing/BlueThistle.webp" /> </div> <div class="student-promo-banner-text-wrapper ml-0 mb-10 text-center text-white"> <div class="h2 mb-10">Get Unlimited Access</div> <div class="h4 font-weight-semi-bold">Try Britannica Premium for free and discover more.</div> </div> <div class="student-promo-banner-button-wrapper d-flex justify-content-center align-items-center ml-auto mr-auto"> <a class="btn btn-m btn-orange" href="https://premium.britannica.com/premium-membership/?utm_source=premium&utm_medium=inline-cta&utm_campaign=august-2024">Subscribe</a> </div> </div> </div> </DIV></div><div class="one-good-fact-module"> </div><span class="marker MOD7 mod-inline"></span> <span class="marker PREMOD8 mod-inline"></span><p class="topic-paragraph">Efforts were also under way to develop more-effective childhood obesity-prevention strategies, including the development of methods capable of predicting infants’ risk of later becoming overweight or obese. One such tool reported in 2012 was found to successfully predict newborn obesity risk by taking into account newborn weight, maternal and paternal BMI, the number of members in the newborn’s household, maternal occupational status, and maternal smoking during <a href="https://www.britannica.com/science/pregnancy" class="md-crosslink autoxref " data-show-preview="true">pregnancy</a>.</p><span class="marker MOD8 mod-inline"></span> </section> <span class="marker end-of-content"></span><span class="marker after-article"></span></div> <div id="chatbot-simplify-root"></div> <div id="chatbot-root"></div> </div> </div> </div> <div class="ai-dialog-placeholder"></div> </div> </div> <aside class="col-md-da-320"></aside> </div> </div> </div> </div> </article> </div> </div> </div> </div> </main> <div id="md-footer"></div> <noscript><iframe src="//www.googletagmanager.com/ns.html?id=GTM-5W6NC8" height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>  <script> window.ap3c = window.ap3c || {}; var ap3c = window.ap3c; ap3c.cmd = ap3c.cmd || []; ap3c.cmd.push(function() { ap3c.init('ZO4siT4cLwnykPnzZWJtd3Byb2Q', 'https://engage.email.britannica.com/'); ap3c.track({v: 0}); }); ap3c.activity = function(act) { ap3c.act = (ap3c.act || []); ap3c.act.push(act); }; var s, t; s = document.createElement('script'); s.type = 'text/javascript'; s.src = "https://engage.email.britannica.com/app.js"; t = document.getElementsByTagName('script')[0]; t.parentNode.insertBefore(s, t); </script> <script class="marketing-page-info" type="application/json"> {"pageType":"Topic","templateName":"DESKTOP","pageNumber":1,"pagesTotal":3,"pageId":423747,"pageLength":1018,"initialLoad":true,"lastPageOfScroll":false} </script> <script class="marketing-content-info" type="application/json"> [] </script> <script src="https://cdn.britannica.com/mendel-resources/3-133/js/libs/jquery-3.5.0.min.js?v=3.133.62"></script> <script type="text/javascript" data-type="Init Mendel Code Splitting"> (function() { $.ajax({ dataType: 'script', cache: true, url: 'https://cdn.britannica.com/mendel-resources/3-133/dist/topic-page.js?v=3.133.62' }); })(); </script> <script class="analytics-metadata" type="application/json"> {"leg":"C","adLeg":"C","userType":"ANONYMOUS","pageType":"Topic","pageSubtype":null,"articleTemplateType":"PAGINATED","gisted":false,"pageNumber":1,"hasSummarizeButton":false,"hasAskButton":true,"hasAiTopQuestions":false,"hasSimplifyButton":false} </script> <script type="text/javascript"> EBStat={accountId:-1,hostnameOverride:'webstats.eb.com',domain:'www.britannica.com', json:''}; </script> <script type="text/javascript"> ( function() { $.ajax( { dataType: 'script', cache: true, url: '//www.britannica.com/webstats/mendelstats.js?v=1' } ) .done( function() { try {writeStat(null,EBStat);} catch(err){} } ); })(); </script> <div id="bc-fixed-dialogue"></div> </body> </html>

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Obesity | Definition, Causes, Health Effects, & Facts | Britannica