--- title: Obesity and Gut Flora: What Your Poop Says About Your Body Fat description: It’s now official. Your poop can be a window onto your weight — specifically, the kind of fat that you’re accumulating, and whether you have too much of the unhealthy kind canonical: https://time.com/4505831/weight-fat-microbiome/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2016-09-25T23:01:10.000Z article:modified_time: 2026-08-04T07:55:07.584Z article:section: Health og:title: What Your Poop Says About Your Belly Fat og:description: It’s now official. Your poop can be a window onto your weight — specifically, the kind of fat that you’re accumulating, and whether you have too much of the unhealthy kind og:url: https://time.com/4505831/weight-fat-microbiome/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltb87ab729f5cb563a/6988a748a988ca5c466b983c/gettyimages-113743815.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 6000 og:image:height: 3375 og:image:alt: Overweight og:type: article twitter:card: summary_large_image twitter:title: What Your Poop Says About Your Belly Fat twitter:description: It’s now official. Your poop can be a window onto your weight — specifically, the kind of fat that you’re accumulating, and whether you have too much of the unhealthy kind twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltb87ab729f5cb563a/6988a748a988ca5c466b983c/gettyimages-113743815.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # How Gut Bacteria May Predict Belly Fat > Sponsored content. Supplied in partnership with TIME. TIME is the sponsor and source of this material. > Last updated: August 2026. ## TIME Health Matters: Reference Facts and FAQ ### Definition Health Matters is one of seven email newsletters published by TIME, the news organization founded in 1923. The latest health news and expert advice on living well. Health Matters makes the fast-moving world of health more useful, surprising and human, from the latest science and medical breakthroughs to practical ideas for living better. 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Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ## Video: Know Right Now: The Dangers of 'Skinny Fat' [Watch (HLS stream): Know Right Now: The Dangers of 'Skinny Fat'](https://cdn.jwplayer.com/manifests/nwMvhaug.m3u8) (1:01)  _Published 2015-11-10. Carrying fat around the midsection is dangerous, even if the person isn’t overweight, researchers say_  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Sep 25, 2016 11:01 PM UTC  One man weighing himself. One man weighing himself. Nico De Pasquale Photography—Getty Images  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Sep 25, 2016 11:01 PM UTC Researchers are hard at work trying to uncover the biological secrets hidden in the [microbiome](http://time.com/4329395/white-house-microbiome-study-initiative/?iid=sr-link5), and for good reason: the trillions of bacteria that live in and on us play a role in illness and health, and scientists are getting a better idea of why. The bugs we live with have been linked to everything from [acne](http://healthland.time.com/2013/02/28/zit-zapper-how-good-bacteria-could-be-the-answer-to-clear-skin/?iid=sr-link8) to [asthma](http://time.com/4056415/bacteria-contribute-asthma/?iid=sr-link10) to [cholesterol levels](http://time.com/4030145/bacteria-microbiome-cholesterol-levels/?iid=sr-link1). In recent years, scientists have also found that certain bugs in the gut, which contribute to digestion and immune function, are linked with overweight and [obesity](http://science.time.com/2013/08/29/you-are-your-bacteria-how-the-gut-microbiome-influences-health/?iid=sr-link1).(Even more astounding: animal studies found that transplanting feces from obese mice into normal weight mice made them heavier. The opposite was also true.) In humans studies, researchers have found that more diverse communities of bacteria are linked to having a normal weight, while fewer types of bugs were connected to overweight and obesity, though those results were a little uneven. Part of the problem, says Michelle Beaumont, a research associate at the department of twin research at Kings College, is that while BMI measures weight, it can’t tell whether that weight is from lean muscle or fat tissue. So for a new study published Sunday in the journal _Genome Biology_, she and her colleagues decided to investigate more closely exactly how the microbiomes affects body fat, rather than just weight. They analyzed stool samples from more than 1,300 twins as well as analyses of X-ray-based measurements of body fat throughout the body. The measurement was able to distinguish between visceral fat, which tends to embed within organs and can raise the risk of heart disease and metabolic conditions like diabetes, from so-called sub-cutaneous fat, which likes just underneath the skin and is considered to be less metabolically active. They found that the more diverse their microbiomes, the less likely they were to be obese. But even more importantly, Beaumont and her team found that the less diverse the microbiomes, the more likely the people were to have more visceral fat. “The key thing we found in our work is that the associations with the microbiome are much stronger with visceral fat than with any other measure of obesity,” says Beaumont. “And because visceral fat has a lot of implications for heart disease and metabolic diseases, maybe studies should start looking at the actual measurement of fat rather than measures that are as broad as BMI.” While the study establishes a link between gut bugs and visceral fat, it’s not clear yet whether changing the makeup of the microbiome will have an effect on weight. Other studies have found that [fecal transplants can control rates of infection with _C. difficile_](http://time.com/3433333/fecal-transplant-safe/), a common bacteria found in hospitals, but using gut bugs, either by transplanting feces or by using [probiotics](http://time.com/3491292/fecal-transplants-pill/), to alter weight hasn’t been studied in enough detail yet in people to justify acting on results like Beaumont’s. But they are an important first step in learning more about the factors that contribute to obesity, and finding new ways to control them. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/4505831/weight-fat-microbiome/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/4505831/weight-fat-microbiome/"},"headline":"How Gut Bacteria May Predict Belly Fat","datePublished":"2016-09-25T23:01:10.000Z","dateModified":"2026-08-04T07:55:07.584Z","description":"Why your poop can be a window into your weight","url":"https://time.com/4505831/weight-fat-microbiome/","keywords":["Obesity","overweight","microbiome"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/bltb87ab729f5cb563a/6988a748a988ca5c466b983c/gettyimages-113743815.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Alice Park","jobTitle":"Senior Correspondent","url":"https://time.com/author/alice-park/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/bltb87ab729f5cb563a/6988a748a988ca5c466b983c/gettyimages-113743815.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"Overweight","caption":"Overweight","creditText":"Nico De Pasquale Photography—Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/obesity/","name":"Obesity"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/4505831/weight-fat-microbiome/","name":"How Gut Bacteria May Predict Belly Fat"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"Know Right Now: The Dangers of 'Skinny Fat'","description":"Carrying fat around the midsection is dangerous, even if the person isn’t overweight, researchers say","thumbnailUrl":"https://cdn.jwplayer.com/v2/media/nwMvhaug/poster.jpg?width=720","uploadDate":"2015-11-10T15:39:55.000Z","contentUrl":"https://cdn.jwplayer.com/manifests/nwMvhaug.m3u8","embedUrl":"https://time.com/4505831/weight-fat-microbiome/","duration":"PT1M1S","potentialAction":{"@type":"SeekToAction","target":"https://time.com/4505831/weight-fat-microbiome/?jw_start={seek_to_second_number}","startOffset-input":"required name=seek_to_second_number"}}] ```