# Even sillier question: Gain or lose weight when you fart? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [August 3, 2023, 9:25pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023 "2023-08-03T21:25:47Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [August 3, 2023, 9:25pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/1 "2023-08-03T21:25:47Z")
Clearly you lose _mass_. That’s not the question. I suspect that the flatus consists of CO2 and CH4. The latter is lighter than air and the former heavier, but I suspect that for people, the CO2 predominates by a lot (I don’t know about cows). So which is it? ---
**Author:** ![Jackmannii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jackmannii/32/311_2.png) [@Jackmannii](https://boards.straightdope.com/u/Jackmannii)\ **Post date:** [August 3, 2023, 9:33pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/2 "2023-08-03T21:33:20Z")
I admit I don’t know, but foresee a hellacious diet book. “Fart Your Way To A Slimmer You: The All-Bean Diet” ---
**Author:** ![CairoCarol](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cairocarol/32/3825_2.png) [@CairoCarol](https://boards.straightdope.com/u/CairoCarol)\ **Post date:** [August 3, 2023, 9:39pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/3 "2023-08-03T21:39:15Z")
Assuming farts have the same density as the air we breathe, I’m gonna go with “neither.” This is my reasoning: You could cup your hands around emptiness (that is, air) and imagine that the chamber you’ve created is airtight. Now, squeeze your palms together and let the trapped air escape. Would this have any impact on your weight? No. ---
**Author:** ![WildaBeast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wildabeast/32/6_2.png) [@WildaBeast](https://boards.straightdope.com/u/WildaBeast)\ **Post date:** [August 3, 2023, 9:56pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/4 "2023-08-03T21:56:22Z")
> [@Hari\_Seldon](#): > > I suspect that the flatus consists of CO2 and CH4. _Mythbusters_ actually analyzed the contents of a flatus once. I’ll see if I can track down their findings. ---
**Author:** ![Folly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/folly/32/3219_2.png) [@Folly](https://boards.straightdope.com/u/Folly)\ **Post date:** [August 3, 2023, 10:06pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/5 "2023-08-03T22:06:23Z")
According to this [cite/site](https://www.ncbi.nlm.nih.gov/books/NBK417/), flatulence is almost all nitrogen, oxygen, carbon dioxide, hydrogen, and methane. The amount of methane is affected by genetics, while the amount of hydrogen is affected by colonic flora\*. It doesn’t really get into percentage ranges though that I can see. \*band name ---
**Author:** ![WildaBeast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wildabeast/32/6_2.png) [@WildaBeast](https://boards.straightdope.com/u/WildaBeast)\ **Post date:** [August 3, 2023, 10:16pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/6 "2023-08-03T22:16:06Z")
> [@Folly](#): > > It doesn’t really get into percentage ranges though that I can see. That’s why I was hoping to find the _Mythbusters_ data – if I remember correctly they did get into percentages for their experiment. Unfortunately, while I can find a lot of sites that state they found the myth “Can you suffocate on your own flatulence?” was busted, none of them go into any details of their test. ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [August 3, 2023, 10:24pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/7 "2023-08-03T22:24:03Z")
This is a great conversation starter for the dinner table. Plus we have beans on the menu tonight. Should be a brisk discussion. I’ll let you know what my geniuses come up with. 🫢 ---
**Author:** ![Spiderman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spiderman/32/230_2.png) [@Spiderman](https://boards.straightdope.com/u/Spiderman)\ **Post date:** [August 3, 2023, 11:35pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/8 "2023-08-03T23:35:11Z")
> [@Beckdawrek](#): > > I’ll let you know what my geniuses come up with. What they come up with at the dinner table…or later on? 😳 ---
**Author:** ![ParallelLines](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/parallellines/32/3575_2.png) [@ParallelLines](https://boards.straightdope.com/u/ParallelLines)\ **Post date:** [August 4, 2023, 3:04am UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/9 "2023-08-04T03:04:50Z")
I too didn’t find a detailed fart summary from Mythbusters, but this [article](https://www.muscleandfitness.com/features/active-lifestyle/anatomy-fart/) says: > 59% nitrogen, 21% hydrogen, 9% carbon dioxide, 7% methane and 4% oxygen—all essentially odorless. (Less than 1% is what makes farts stink.) ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [August 4, 2023, 3:32am UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/10 "2023-08-04T03:32:34Z")
> [@CairoCarol](#): > > Assuming farts have the same density as the air we breathe, I’m gonna go with “neither.” It’s gas under pressure (relative to the outside air), so it’ll be denser than the same gases once they’re released. For that reason, I’ll guess that you lose weight during the event. ---
**Author:** ![Sauron](https://avatars.discourse-cdn.com/v4/letter/s/ce7236/32.png) [@Sauron](https://boards.straightdope.com/u/Sauron)\ **Post date:** [August 4, 2023, 11:48am UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/11 "2023-08-04T11:48:14Z")
Didn’t Cecil write a column on this years ago? I’ll track it down later if I have time (and if it exists). ---
**Author:** ![RitterSport](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rittersport/32/6326_2.png) [@RitterSport](https://boards.straightdope.com/u/RitterSport)\ **Post date:** [August 4, 2023, 11:58am UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/12 "2023-08-04T11:58:16Z")
It must be that you lose weight. First of all, as the OP says, you lose mass, but I doubt you become any less buoyant – that is, you don’t float more in the air due to being denser, to offset the mass lost. As @Robot_Arm mentions, that gas is under pressure. When you fill up a balloon with air, it weighs more than an empty balloon. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 4, 2023, 12:36pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/13 "2023-08-04T12:36:15Z")
> [@RitterSport](#): > > When you fill up a balloon with air, it weighs more than an empty balloon. The balloon is the exact analogy as it depends on what gas it is filled up with. Helium filled balloons float remember. That calculation is not complex even if I’m too lazy to do it, assuming those percentages are correct. I _highly_ doubt intestinal gases are under enough pressure to significantly change density. Given how much more hydrogen and methane than room air I’d guess less … _except_ even a few … um … bits of particulate material … in there easily fill the scale the other way. And I am quite sure most farts have some aerosolized solids. Lose weight. ---
**Author:** ![RitterSport](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rittersport/32/6326_2.png) [@RitterSport](https://boards.straightdope.com/u/RitterSport)\ **Post date:** [August 4, 2023, 12:38pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/14 "2023-08-04T12:38:12Z")
> [@DSeid](#): > > aerosolized solids. Ew. 🤢 ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [August 4, 2023, 12:58pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/15 "2023-08-04T12:58:00Z")
And even if you don’t want to think about that, there is a higher _water vapor_ content of any gases in the body than in room air, which also adds significantly to density relative to room air. A factor to consider in the other direction though is _temperature_? Internal gas is often warmer than room air so less dense. ---
**Author:** ![Thudlow\_Boink](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thudlow_boink/32/320_2.png) [@Thudlow\_Boink](https://boards.straightdope.com/u/Thudlow_Boink)\ **Post date:** [August 4, 2023, 1:03pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/16 "2023-08-04T13:03:21Z")
I assume that, if you’ve been drinking [Fizzy Lifting Drinks](https://wonka.fandom.com/wiki/Fizzy_Lifting_Drinks), farting makes you gain weight. ---
**Author:** ![hibernicus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hibernicus/32/2802_2.png) [@hibernicus](https://boards.straightdope.com/u/hibernicus)\ **Post date:** [August 4, 2023, 1:38pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/17 "2023-08-04T13:38:04Z")
In order to establish whether the release of gas results in an increase or reduction of your measured weight, you would need to consider both the change in mass (i.e. the mass of gas released) and the change in volume of your body. Buoyancy is relevant here to what we mean by “lose weight”. Even dense objects such as iron nails will weigh slightly less if weighed in air than in vacuum due to the weight of the air they displace (the difference is slight but is real and measurable, and must be allowed for when carrying out very precise measurements). I doubt very much if the gases inside your body are pressurised to any great extent. The sphincters that retain the contents of your alimentary canal would not be able to withstand any significant pressure difference. I haven’t been able to find any numbers though. ---
**Author:** ![Sauron](https://avatars.discourse-cdn.com/v4/letter/s/ce7236/32.png) [@Sauron](https://boards.straightdope.com/u/Sauron)\ **Post date:** [August 4, 2023, 4:31pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/18 "2023-08-04T16:31:16Z")
[Cecil’s take](https://www.straightdope.com/21342003/do-you-weigh-more-or-less-after-you-fart): You may weigh an infinitesimal bit more (although his answer wasn’t as definitive as I remembered it being). ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 4, 2023, 4:51pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/19 "2023-08-04T16:51:22Z")
> [@ParallelLines](#): > > I too didn’t find a detailed fart summary from Mythbusters, but this [article](https://www.muscleandfitness.com/features/active-lifestyle/anatomy-fart/) says: > > > 59% nitrogen, 21% hydrogen, 9% carbon dioxide, 7% methane and 4% oxygen—all essentially odorless. (Less than 1% is what makes farts stink.) Normal air, assuming 78% nitrogen and 22% oxygen, will have an average molecular mass of around 28.9. That mixture of gases (assuming the percentages are by moles, which would make sense for gases) will have an average molecular mass of around 22.2. The flautus gases will be pressurized some inside the body, but to pressurize them enough to get the same density, you’d need to be able to sustain a pressure difference of 0.3 atmospheres, which seems highly implausible. So flautus gases in your gut will, in fact, be buoyant. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 4, 2023, 4:56pm UTC](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023/20 "2023-08-04T16:56:34Z")
Oh, and to expand on that: If those proportions are actually by mass, that means a larger number of the smaller molecules, and a smaller number of larger molecules, which would mean an even lower overall density. And I was also assuming an equal temperature for internal flautus and the ambient air, but the interior temperature is almost certainly going to be higher. There’s also water vapor to consider, but that’s an even lighter gas than the average of the given gases (molecular mass of 18), so assuming a given pressure (air pressure plus whatever the maximum pressure difference is the gut can maintain), that’ll make our flautus even more buoyant. So to the extent that my figure is off, the answer will certainly still be buoyancy. [Next page](https://boards.straightdope.com/t/even-sillier-question-gain-or-lose-weight-when-you-fart/988023.md?page=2)