Even though it was named one of the worst health trends of 2019, the keto diet is still (somehow) going strong. The low-carb, high-fat, high-protein eating plan was originally developed to treat epilepsy. But at some point, it caught fire in the fitness world. People started saying that ditching carbs altogether boosted their energy and helped them gain muscle. Eventually celebs like Kourtney Kardashian, Jersey Shore's Vinny Guadagnino, and LeBron James hopped on the bandwagon. Little (and not-so-little) keto communities started popping up all over the place IRL and online. In these convos, however, a curious trend started to emerge: odor.
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Specifically, a sudden change — for the worse — in body odor, sometimes accompanied by halitosis. One Reddit user described the smell similar to that of bacon while another user has said that their new stench "kind of smells like fat is soaking into my sweat."
Despite how common this side effect seems to be (people affectionately refer to it as "keto breath"). There isn't a ton of info out there about exactly why it happens, but Robert Graham, MD, co-founder of FRESH Med, gave us a clue.
"When the body is in ketosis, it produces these chemicals called ketones," he explains. Ketones exit the body via your breath, and some through your sweat. One of these ketones is known as acetone, he says. Yep, you read that right — acetone, the same stuff that's in nail polish remover. And, as you may remember from your nail art nights, acetone smells atrocious.
Entering ketosis will increase the amount of ketones, like acetone, present in your breath. One new test developed by Technical Research Center of Finland actually determines whether your body is in ketosis or not by testing acetone levels in exhaled breath.
As of now, no studies have proven that the acetone is definitely responsible for the "keto smell." But Dr. Graham says it's pretty likely that the ketone is to blame. Though, he says, there may be other factors at play.
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"Any sort of dietary change alters your whole physiology and thus changes your pH, which can affect everything," Dr. Graham says. Translation: Though keto's effect on your BO may be uniquely horrible, any radical change in your eating patterns could cause you to smell differently. If you start eating a ton of cruciferous veggies, for example, you may notice your body odor gets stronger (and possibly more unpleasant) due to increased levels of sulfur from the produce.
Along with general body odor, there have been concerns about whether or not the keto diet can throw off your vaginal pH, causing an unpleasant scent known as "keto crotch." But in general, there's limited data about the way that a person's diet affects their vaginal health, Caroline Mitchell, MD, director of the vulvovaginal disorders program at Massachusetts General Hospital, previously told Refinery29.
If the possibility of scaring off friends and family with your newfound smelliness doesn't quash your curiosity about keto and you try it, Dr. Graham suggests drinking plenty of water. That will cause you to urinate more, flushing out ketones and minimizing odor.
But to be honest, odor is the least of what's wrong with keto. The diet itself is extremely restrictive, and deprives you of key macronutrients that make up a healthy diet. A recent study even found that long-term adherence can increase your risk of all-cause mortality. So on that note, if you're really thinking about getting on board this trend, definitely talk to a doctor first and weigh all of the stinkin' risks.