There are still many misunderstandings about the ketogenic diet to this day. Simply put, ketosis is your body's metabolic state when you consume a diet high in fat, moderate in protein and low in carbohydrates. Ketones are produced when your body transitions from burning glucose (sugar) to burning fat. The 'state of ketosis' is therefore a status of fat burning. This is a completely natural state on which humanity has thrived for the vast majority of evolutionary existence.
In short, energy from ketosis can be seen as an alternative energy source. Various studies indicate that this form of energy supply for muscles, heart, liver and brain is preferable to a carbohydrate-rich diet. In ketosis you get energy from your body-fat as well as from the fat from your diet. In addition to the obvious benefits of weight optimization, it can also have beneficial effects on your metabolism, cognition, performance, and in aiding to stave off and reduce inflammation and aging.
The list of ketosis benefits is growing as more research is being performed. These are some of the most obvious benefits:
- Control over hunger
- Effortless weight loss and weight maintenance
- Mental sharpness
- Deep sleep
- Stable blood sugar levels and insulin sensitivity
- Low LDL cholesterol (generally bad)
- High HDL cholesterol (generally good)
- More energy
- Increased sex drive
- Stronger immune system
- Slowed aging
- Improvements in blood composition
- Better memory
- Faster recovery after movement
- Fewer mood swings
If you want to read up on how ketosis influences brain function have a look here. You can find an article on the positive effects on the gut microbiome as well.
This question is difficult to answer because every person has a different carbohydrate tolerance level. Especially (top) athletes can stay in ketosis with up to 100 grams of carbohydrates per day. However, most people will have to eat less than 50 carbohydrates a day, especially if their metabolism has not yet been adjusted to this shift. It is important to regularly measure your ketone values to see how your body responds to certain macro-nutrient ratios.
Your body needs a certain amount of time to switch to fats. This can certainly have a number of adverse effects in the initial phase. Fatigue and a lack of sharpness can appear in the first days or even weeks. In addition, you can experience bad breath during this period. The body stores a lot of toxins in fat and when these fats are burned, the liver has to process these substances. This is a temporary phase and is more than worth going through. When your system is adjusted, the fatigue and bad breath will disappear and the sharpness will return. If the fatigue persists, this can also be related to your salt intake. Most people need about 5-7 grams of salt every day with a keto diet.
Also, there is a phenomenon called the keto flu, and if you want to know how to overcome it, have a look over at this page.
Nothing is perfect and neither is ketosis. When you go extremely low in carbohydrates for months, you run the risk of elevated cortisol levels and muscle being broken down into glucose for the brain. You can recognize these symptoms by dry eyes and when your quality of sleep deteriorates. Going in and out of ketosis cyclically can therefore have advantages, in particular because some cells function better on ketones (neurons) and others better on glucose (myelin repair). It can therefore be beneficial to maintain mild ketosis without completely lowering your carbohydrates. This can be done, for example, with MCT oil or with exogenous ketones. These are taken up directly in the liver and processed immediately. The glycogen stores are 'dumped' and you can get into ketosis very quickly, even if carbohydrates are present.
Another option is to include some targeted re-feeding of carbohydrates after workouts. The approach of Ben Greenfield, one of the worlds most renowned keto- and performance experts is the following:
Eating zero net carbs the entire day until post-workout feeding, which is a dinner that typically occurs with 1-3 hours after a 30-60 min workout that falls sometime between 4:30 and 6:30 pm.
I then re-feed with starches up to 150-200g from sources such as millet, sweet potato, yam, white rice, red wine, dark choclate etc.
I then intermittent fast for 12-16 hours, then rinse, wash, and repeat.
If you like to see more content of Ben, where he also addresses some more advanced FAQ's related to ketosis, check out his article here.
Correlation between blood ketones (beta-hydroxybutyrate - BHB) and breath ketones (acetone - BrAce) only exists in certain controlled situations. For example with a sample that is not adapted to a low carbohydrate diet and does not take food for 12+ hours. Usually, there is no direct correlation between ketones in the breath and the blood. This is because acetone continuously leaves the body through the breath and a small portion is broken down in the liver. This makes it a real-time indicator of the ketones. No buffer is built up. BHB blood ketones, on the other hand, are formed from the excess acetoacetate and are buffered in the blood and are the result of time and ketosis. BHB can also be converted back to acetoacetate and be used as an energy form. These differences make it impossible to speak of a correlation between ketones in the breath and the blood. So you can see it like this: If you measure a high ketone value in your breath, it is more likely you will get a high concentration of BHB in due time.
For a long time, blood ketone measurement has been considered the gold standard. This is because the increase of BHB levels in the blood is higher than the ris in acetone and acetoacetate, and is therefore a more obvious indicator. Nitroprusside testing of ketosis of urine through reagent strips for example, has been claimed to detect only 22% of the ketones that are present during ketosis. A reliable way to test your blood ketones is with the keto mojo meter.
More and more research is being done that shows that breath measurements are equally reliable as other methods. Studies show that you can measure ketones in breath for fat loss, and the breath measurements are at least as reliable as the urine test strips.¹ˈ²
When you really get used to using ketones as your main source of energy, take enough electrolytes in the form of potassium and sodium, and if you have an adequate protein intake there need not be any negative side-effects. There may even be benefits.³ A ketogenic diet in combination with strength training leads to a stronger increase in testosterone and fat free mass in men than a standard carbohydrate-rich diet.⁴
Do you have other questions that are not addressed here, please let us know in the comments below!
1. Anderson J. C. (2015). Measuring breath acetone for monitoring fat loss: Review. Obesity (Silver Spring, Md.), 23(12), 2327–2334. https://doi.org/10.1002/oby.21242
2. Kathy Musa-Veloso, Sergei S Likhodii, Stephen C Cunnane, Breath acetone is a reliable indicator of ketosis in adults consuming ketogenic meals, The American Journal of Clinical Nutrition, Volume 76, Issue 1, July 2002, Pages 65–70, https://doi.org/10.1093/ajcn/76.1.65
3. Phinney, S.D. Ketogenic diets and physical performance. Nutr Metab (Lond) 1, 2 (2004). https://doi.org/10.1186/1743-7075-1-2
4. Wilson JM, Lowery RP, Roberts MD, et al. The Effects of Ketogenic Dieting on Body Composition, Strength, Power, and Hormonal Profiles in Resistance Training Males. Journal of Strength and Conditioning Research. 2017 Apr. DOI: 10.1519/jsc.0000000000001935.
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