Resource (1) below, Measuring breath acetone for monitoring fat loss: Review [PubMed Abstract], is an excellent resource about ketosis.
Here are some excerpts from the article:
Like carbon dioxide, acetone is a by-product of metabolism. By
itself, the presence of acetone in exhaled breath does not indicate
underlying disease. Low concentrations (1 to 2 ppm) of breath acetone represent a basal level of ketosis. High levels of breath acetone (75 to 1,250 ppm), associated with diabetic ketoacidosis, represent the other end of the breath acetone spectrum. Between these extremes lie healthy individuals participating in high-fat, low-carbohydrate (HFLC) diets, calorie restriction diets, and fasting. Their BrAce can span two orders of magnitude (Figure 1).
The amount of caloric restriction has the next greatest impact on
BrAce. Fasting, the extreme form of caloric restriction, can elevate BrAce, up to 170 ppm over the course of weeks, more than macronutrient changes in adults (Figure 1). However, fasting is not a sustainable lifestyle whereas a HFLC diet can be a lifestyle that leads to long term elevated acetone levels.
Less extreme than fasting is moderate caloric restriction which
allows some food intake and appears to cause modest changes in breath acetone. Breath acetone levels rise as stored fat is metabolized to make up the difference between basal energy requirements and caloric intake. Using caloric restriction, multiple studies have shown a correlation between fat loss and increases in breath acetone (8,24,25,27,29). Specifically, individuals that maintain a breath acetone of 2 ppm should realize a fat loss rate of at least 114-227g week21, based on the scientific literature (8,27,29). On the high end, BrAce could reach 8 ppm which could correspond to a fat loss of 1,200 g week21 (8).
While not as powerful as caloric restriction, exercise affects breath acetone near the time of exercise and over the course of days. During exercise, breath acetone can increase by approximately 1 ppm depending on the initial state of ketosis, intensity, and duration (44-46,50). In the hours following exercise, breath acetone is expected to increase based on the behavior of BOHB (49); however, confirmatory studies are needed. Acutely, exercise-induced increases in fat metabolism are expected to drive BrAce (44,50). Over days, daily exercise can elevate breath acetone because exercise consumes calories
of energy. If the daily caloric intake remains constant, exercise
increases the number of calories required to maintain current body weight. Thus, exercise can cause calorie restriction which will lead to increases in BrAce as stored fat is metabolized to make-up the energy deficit (24,25,29). It is assumed that the effects of exercise on BOHB would represent the effects of exercise on BrAce since both BOHB and BrAce are closely correlated ketone bodies. However, more investigations are needed to confirm the direct impact of exercise on breath acetone.
Endogenous breath acetone is correlated with and can be used to understand the rate of fat loss in healthy subjects. Maintaining a 2 ppm BrAce while on a calorie restriction diet should cause a fat loss rate of 227 g week21. Acetone is correlated with fat loss because it and two other ketone bodies are the by-products of fat metabolism. Breath acetone is strongly correlated with the blood ketone body BOHB. Breath acetone can range in concentration from 1 ppm in healthy non-dieting subjects to 1,250 ppm in diabetic ketoacidosis. In healthy individuals, breath acetone is affected by multiple factors. Dietary macronutrient composition has the greatest impact
followed, in rank order, by caloric restriction, exercise, pulmonary factors, and other factors. Because of its relationship to fat metabolism, a high-fat, low-carbohydrate diet will generate more breath acetone than a standard mixed diet. A reduction in consumed calories relative to that needed for weight maintenance can increase breath acetone and fat loss. Exercise can promote caloric restriction. Additionally, exercise can cause breath acetone elevation during a workout. Human respiratory factors can affect the acetone concentration in the breath sample. Other foods (e.g., garlic), drugs (e.g., disulfiram), and environmental conditions can increase breath acetone
due to their ability to increase fat metabolism or block acetone
metabolism. While the relationship between breath acetone and fat loss is well established, additional research is needed to better understand these factors and advance this area of integrative physiology.O
Resource (2), Monitoring for compliance with a ketogenic diet: what is the best time of day to test for urinary ketosis? [PubMed Abstract]:
The ketogenic diet (KD) is a very low-carbohydrate, high-fat and adequate-protein diet with no calorie limit that induces a metabolic condition called “physiological ketosis”. It was first introduced to treat epilepsy in the 1920s and has become quite popular recently as weight-loss and performance-enhancing diet. Its therapeutic use in a range of diseases is under investigation. During KD interventions people are supposed to monitor compliance with the dietary regimen by daily urine testing for ketosis. However, there are no studies investigating the best time for testing.
Twelve healthy subjects (37 ± 11 years; BMI = 23.0 ± 2.5 kg/m2) were instructed to, during the sixth week of a KD and with stable ketosis, measure their urine (8×) and blood (18×) ketone concentration at regular intervals during a 24-h period. According to their 1-day food record, the subjects consumed on average a diet with 74.3 ± 4.0 %, 19.5 ± 3.5 %, and 6.2 ± 2.0 % of total energy intake from fat, protein and carbohydrate, respectively. The lowest blood ß-hydroxybutyrate (BHB) (0.33 ± 0.17 mmol/l) and urine acetoacetate (AA) (0.46 ± 0.54 mmol/l) concentrations were measured at 10:00, respectively. The highest BHB (0.70 ± 0.62 mmol/l) and AA concentrations were noted at 03:00, respectively. Via urine testing the highest levels of ketosis were found at 22:00 and 03:00 and the highest detection rates (>90 %) for ketosis were at 07:00, 22:00 and 03:00, respectively.
These results indicate that ketonuria in subjects with stable ketosis is highest and can be most reliably detected in the early morning and post-dinner urine. Recommendations can be given regarding precise time of the day for measuring ketone bodies in urine in future studies with KDs.
(1) Measuring breath acetone for monitoring fat loss: Review [PubMed Abstract] [Full Text HTML] [Full Text PDF]. Obesity (Silver Spring). 2015 Dec;23(12):2327-34. doi: 10.1002/oby.21242. Epub 2015 Nov 2.
(2) Monitoring for compliance with a ketogenic diet: what is the best time of day to test for urinary ketosis? [PubMed Abstract] [Full Text HTML] [Full Text PDF]. Nutr Metab (Lond). 2016 Nov 4;13:77. eCollection 2016.