# Losing weight gives you bad breath?
**URL:** https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636
**Category:** Factual Questions
**Created:** [February 2, 2006, 4:50am UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636 "2006-02-02T04:50:28Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@Rodgers01](https://boards.straightdope.com/u/Rodgers01)
#### Post date: [February 2, 2006, 4:50am UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/1 "2006-02-02T04:50:28Z")
I turned on the radio the other day, and heard a guy claiming that when people lose weight, the fat cells in their body, as they’re dying (breaking up? shrinking?) release a foul smelling odor that escapes through the mouth, giving you bad breath. (I don’t think he was claiming that this is the primary cause of bad breath; just one of several.)
Any truth in this theory? Should I take a Certs next time I go to the gym?
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### Author:  [@Boo\_Boo\_Foo](https://boards.straightdope.com/u/Boo_Boo_Foo)
#### Post date: [February 2, 2006, 4:57am UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/2 "2006-02-02T04:57:46Z")
It’s very true. I believe it’s called “ketosis” - a process where the body is metabolising body fat in real time to top up our blood sugar levels.
Amongst some pro road cycling friends of mine, every year around this time, the syndrome is very common as they get leaner and leaner as their weekly mileage starts ramping up and up.
I’ve know it myself over the years too. Your breath has a kind of “nail remover” smell to it.
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### Author:  [@sandra\_nz](https://boards.straightdope.com/u/sandra_nz)
#### Post date: [February 2, 2006, 5:39am UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/3 "2006-02-02T05:39:46Z")
Doesn’t that only occur with a low-carb diet such as Atkins? Someone who’s losing weight merely through more exercise/less food wouldn’t necessarily have this condition.
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### Author:  [@Mindfield](https://boards.straightdope.com/u/Mindfield)
#### Post date: [February 2, 2006, 4:58pm UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/4 "2006-02-02T16:58:16Z")
That’s how I understand it. Ketosis only (or primarily) occurs when you are on a low-carb diet that forces your body to metabolize fat for energy. If you’re just dieting in the traditional sense (that is, eating low-fat, low calorie foods and excersizing) there shouldn’t be anything unusual going on with your body – with the possible exception of some extraordinarily foul stuff evacuating your bowels as your body starts shedding the crap it doesn’t need anymore.
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### Author:  [@Mindfield](https://boards.straightdope.com/u/Mindfield)
#### Post date: [February 2, 2006, 4:59pm UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/5 "2006-02-02T16:59:24Z")
- ahem.
Pun unintentional. My apologies.
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### Author:  [@rowrrbazzle](https://boards.straightdope.com/u/rowrrbazzle)
#### Post date: [February 2, 2006, 10:23pm UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/6 "2006-02-02T22:23:22Z")
Ketosis and the associated “fruity” breath can also occur in diabetics and after drinking booze.
> **[Alcohol and health](https://en.wikipedia.org/wiki/Effects_of_alcohol_on_the_body#Excessive_doses)**
>
> Alcohol (also known as ethanol) has a number of effects on health. Short-term effects of alcohol consumption include intoxication and dehydration. Long-term effects of alcohol consumption include changes in the metabolism of the liver and brain, several types of cancer and alcohol use disorder. Alcohol intoxication affects the brain, causing slurred speech, clumsiness, and delayed reflexes. Alcohol stimulates insulin production, which speeds up glucose metabolism and can result in low blood sug...
> [@](#):
>
> Severe drunkenness and diabetic coma can be mistaken for each other on casual inspection, with potentially serious medical consequences for diabetics. The major physical finding they share is the sickly-sweet odour of ketosis on the breath; alcoholic ketosis and diabetic ketosis are both marked by the presence of acetone and other ketones in the bloodstream, although the ketones are produced by different metabolic pathways in each disorder.
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### Author:  [@FilmGeek](https://boards.straightdope.com/u/FilmGeek)
#### Post date: [February 2, 2006, 10:53pm UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/7 "2006-02-02T22:53:19Z")
After being on Atkins last year, my fiance and I both had really terrible breath. Truly shitty breath… definitely the worst side effect. It was not the fruity or acetone smell most people associate with ketosis.
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### Author:  [@Boo\_Boo\_Foo](https://boards.straightdope.com/u/Boo_Boo_Foo)
#### Post date: [February 3, 2006, 2:44am UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/8 "2006-02-03T02:44:31Z")
> [@Mindfield](#):
>
> That’s how I understand it. Ketosis only (or primarily) occurs when you are on a low-carb diet that forces your body to metabolize fat for energy. If you’re just dieting in the traditional sense (that is, eating low-fat, low calorie foods and excersizing) there shouldn’t be anything unusual going on with your body – with the possible exception of some extraordinarily foul stuff evacuating your bowels as your body starts shedding the crap it doesn’t need anymore.
Nope… ketosis occurs WHENEVER your blood sugar levels reach a lower threshold point - regardless of your diet make up. Ketosis, as I noted earlier, is a function of depleted glycogen in your liver and muscle stores. It takes place regardless of what your diet makeup is, whether it be Atkins or Fatkins or Chatkins.
If your glycogen stores are low, your body says “ooops, my blood sugar levels are getting precariously low - time to burn body fat in real time to prop up the blood glucose levels…” This is why my pro cyclist buddies go through it so badly in January through March as they ramp up to over 1,000km per week on the bike and yet ALSO limit their calorie intake. Essentially, their bodies are in slight starvation mode - particularly during their sleep - because that’s when the greatest amount of “body fat to liver glycogen” conversion takes place.
Ketosis is the opposite of when your blood sugar levels are too high. When your blood sugar levels climb too high - for example, after eating a truckload of calories, at that point, insulin is released to start the blood glucose to body fat conversion process.
It should be noted that ketosis primarily is a morning thing - because we just fasted for 8 to 9 hours. It becomes very pronounced in athletes who are cutting down as they come into their season. But it’s a myth that it’s determined by your carb vs protein vs fat ratios. It’s purely dependant on your glycogen levels.
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### Author:  [@Yeeter](https://boards.straightdope.com/u/Yeeter)
#### Post date: [February 3, 2006, 1:16pm UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/9 "2006-02-03T13:16:07Z")
When I was on a diet through Medical Weight Loss Center, they would have me occaisionally pee on a strip to make sure I was not going into ketosis. They told me it was to make sure I was not cheating – my assumption being that maybe some people did not follow their prescribed diet and would just skip meals, so that they would meet their wieght targets daily, sending the body into ketosis .
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### Author:  [@Annie-Xmas](https://boards.straightdope.com/u/Annie-Xmas)
#### Post date: [February 3, 2006, 1:21pm UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/10 "2006-02-03T13:21:44Z")
In a statement defending his diet, Dr. Atkins said it gave breath an “unusual” odor that he didn’t even notice it in his patients anymore because he considered it “normal.”
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### Author:  [@SenorBeef](https://boards.straightdope.com/u/SenorBeef)
#### Post date: [February 4, 2006, 11:51pm UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/11 "2006-02-04T23:51:55Z")
The bad breath issue can be negated pretty much entirely by increasing your water intake. Ketone byproducts mostly get excreted through urine.
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### Author:  [@mr.jp](https://boards.straightdope.com/u/mr.jp)
#### Post date: [February 8, 2006, 9:28pm UTC](https://boards.straightdope.com/t/losing-weight-gives-you-bad-breath/342636/12 "2006-02-08T21:28:41Z")
You people are right about it being caused by the breakdown of fat. It is not, however, because the fat cells are dying. Neither because the body is turning up the glucose level. In fact it is caused by the body not being able to convert fat into glucose. Instead it produces ketone bodies, which can enter the Krebs cycle and give energy. And, they smell.