Uncovering the Truth: Why Do People Smell on Keto?

January 13, 2026 •

4 min read

Did you know that up to a third of people on a ketogenic diet report experiencing a change in body odor? This unpleasant phenomenon, which leads many to wonder why do people smell on keto, is a common, though temporary, side effect of shifting your body's metabolism from burning carbs to fat.

Quick Summary

The distinct smell during ketosis is caused by excess ketones, particularly acetone, which is released through breath and sweat as the body burns fat for fuel. Contributing factors include hydration levels, protein intake, and gut bacteria changes.

Key Points

Ketone Excretion: Excess acetone, a ketone body byproduct of fat burning, is released through breath and sweat, causing a characteristic fruity or chemical odor.
Hydration is Key: The diuretic effect of keto can lead to dehydration, concentrating sweat and urine and intensifying any body odor.
Macronutrient Balance: Consuming too much protein on a keto diet can cause an ammonia-like smell as a metabolic byproduct.
Temporary Phase: The odor is most pronounced during the initial adaptation period and typically fades within a few weeks as the body becomes more efficient at using ketones.
Distinguish from DKA: A simple, temporary change in odor is normal for ketosis, but an intense, persistent fruity breath combined with other symptoms could indicate dangerous diabetic ketoacidosis.
Manage with Hygiene and Diet: Strategies like increased hydration, good oral hygiene, and balanced macros can help mitigate the odor effectively.

The Metabolic Shift: Why Ketones Cause Odor

When you follow a ketogenic diet, you drastically reduce your carbohydrate intake, forcing your body to find an alternative fuel source. This process, known as ketosis, involves the liver breaking down fat into molecules called ketone bodies. There are three main types of ketone bodies: acetoacetate, beta-hydroxybutyrate, and acetone.

Acetone is the most volatile of these ketones and is the primary culprit behind the unique odor. It is released from the body through respiration (breath) and perspiration (sweat). Because acetone is a component of nail polish remover, the smell is often described as fruity, sweet, or chemical-like. This is not a sign of poor hygiene but rather a direct result of your body's new metabolic state.

The 'Keto Flu' and Odor Intensity

During the initial phase of a ketogenic diet, often called the 'keto flu,' the body is not yet efficient at utilizing ketones for energy. This inefficiency leads to a surplus of ketones, which are then excreted, making the odor most noticeable. As the body becomes 'fat-adapted' and more effective at using ketones, the excess production decreases, and the smell typically subsides. This adaptation period can take anywhere from a few weeks to a month or more.

Other Dietary Factors That Contribute to Body Odor

While ketones are the main driver, other aspects of the keto diet can exacerbate the smell. It is not solely about the acetone, but a combination of metabolic changes.

Dehydration: The ketogenic diet has a diuretic effect, especially at the beginning, leading to increased water and electrolyte excretion. When you are dehydrated, your sweat and urine become more concentrated, intensifying any existing odor. The loss of saliva that comes with dehydration can also worsen bad breath.
Excess Protein Intake: The keto diet emphasizes moderate protein, not high protein. If you consume too much protein, your body may produce ammonia as a byproduct of metabolism. This ammonia can be excreted through sweat and breath, causing a pungent, bleach-like smell. Ensuring you are hitting your fat macro goals is crucial to avoid this.
Changes in Gut Bacteria: Significant dietary shifts can alter the balance of bacteria in your gut. This change in the microbiome can affect the metabolism of certain compounds, which in turn can contribute to changes in your body odor. Adding probiotic-rich foods can help mitigate this.

Managing and Mitigating the Odor

Fortunately, you don't have to simply tolerate the smell until it goes away. Here are several actionable strategies to help manage the odor while remaining in ketosis:

Stay Hydrated: Drink plenty of water throughout the day. This helps flush excess ketones from your system and keeps sweat and urine diluted, reducing the odor's concentration. Adding lemon or mint to your water can also offer a refreshing boost.
Optimize Oral Hygiene: While not a cure, a solid oral hygiene routine is essential. Brush your teeth frequently, floss daily, and use a tongue scraper to remove odor-causing bacteria. Opt for sugar-free gum or mints, preferably with xylitol, for quick breath freshening.
Adjust Macronutrients: Ensure you are not overconsuming protein. Double-check your macro ratios to ensure you are getting adequate fat and not relying too heavily on protein for satiety.
Increase Fiber-Rich Foods: Incorporate more low-carb, fiber-rich vegetables into your diet. This can promote saliva production and contribute to a healthier gut microbiome, which may reduce odor.
Wear Breathable Fabrics: Choose clothing made from natural, breathable materials like cotton or linen. These fabrics help your skin breathe and minimize the buildup of odor-causing bacteria on your body.

Keto Odor vs. Diabetic Ketoacidosis: Understanding the Difference

It is crucial to distinguish between the mild, temporary odor of nutritional ketosis and the very serious condition known as Diabetic Ketoacidosis (DKA). While both involve elevated ketones, they have distinct characteristics.


Feature	Nutritional Ketosis	Diabetic Ketoacidosis (DKA)
Cause	Normal metabolic response to a low-carb diet.	Very high blood sugar and severe insulin deficiency.
Odor	Mild to moderate, fruity or chemical smell.	Strong, persistent, and intense fruity breath.
Associated Symptoms	Mild 'keto flu' symptoms, temporary fatigue.	Severe symptoms like nausea, vomiting, abdominal pain, high blood sugar, and confusion.
Ketone Levels	Moderate levels of ketones.	Dangerously high levels of ketones, making blood acidic.
Action Required	Implement lifestyle changes like increased hydration.	Medical emergency requiring immediate hospitalization.

Conclusion: A Temporary Symptom of Adaptation

Understanding why you smell on keto can alleviate concern and empower you to manage the side effect effectively. The odor, primarily from acetone excretion during the initial phase of ketosis, is a temporary signal that your body is successfully adapting to its new fat-burning fuel source. By staying hydrated, maintaining excellent hygiene, balancing your macros, and being patient, you can successfully navigate this common transition. However, if the odor is intense and accompanied by concerning symptoms, especially for those with diabetes, it is crucial to seek medical advice to rule out more serious conditions like DKA.

To learn more about ketones in the body, you can refer to authoritative sources like the Cleveland Clinic.

Frequently Asked Questions

The smell is caused by the metabolic byproduct acetone, which is expelled through breath and sweat as your body switches to burning fat for fuel.

The odor is usually temporary and tends to diminish within a few weeks as your body becomes more efficient at using ketones for energy, a state known as being 'fat-adapted'.

Yes, staying well-hydrated helps flush excess ketones from your system through urination and keeps sweat and urine diluted, reducing the intensity of the odor.

Yes, a very high protein intake can cause the body to produce excess ammonia as a byproduct of metabolism, which can intensify the body odor.

For a non-diabetic person, a mild, temporary odor is a normal sign of nutritional ketosis. However, if the smell is very strong and accompanied by other severe symptoms, it could indicate diabetic ketoacidosis (DKA), which requires immediate medical attention.

Incorporating fiber-rich, low-carb vegetables and fresh herbs like parsley and mint can help. Probiotic-rich foods may also help balance gut bacteria, which can influence body odor.

While regular brushing, flossing, and tongue scraping are essential for overall oral health and can help mask odor, they won't completely eliminate keto breath, which comes from acetone being exhaled from the lungs.

No, not everyone on a ketogenic diet experiences the same degree of body odor. The intensity and type of odor can vary from person to person, depending on individual physiology.