Does Carb Content Affect Ketosis? I Volunteered in a Study to Find Out

One of my favorite things about working at LifeOmic is that we immerse ourselves into making the biggest impact on people’s health and wellness journey possible. With an embedded science and medical team, I get the opportunity to sit side-by-side with experts in the field to understand their methods, pain points, goals, as well as some of the more complicated science and health related topics on a deeper level. Sometimes we even get the opportunity to participate in studies, and I always jump on this opportunity because it helps us learn more about the field and it gives me a chance to understand more about myself. 

I recently participated in a study to test several ketone and blood glucose measurement devices through four 24-hour fasts. There are a lot of options for devices in the market, so how do you know which is best for you? Do they all provide similarly accurate results? Does what you eat have an impact on how fast you reach ketosis? I was excited to help test the devices and learn how my body reacted to different meal compositions. 

I and 11 other LifeOmic employees volunteered to test six devices: Keto-Mojo, Ketosense and Precision Xtra which measure ketones in blood; and Keyto, Biosense, and Ketonix, which measure breath ketones.  Prior to starting the fasts, we ate either a low-carb meal or a high-carb meal. We made the measurements when we began our fast and after 12, 16, 20 and 24 hours. 

Here’s what I learned from this experiment:

A high-carb pre-fast meal delayed my entry into ketosis but didn’t affect my hunger levels or sleep

My first 24-hour fast started with an intentionally high-carb meal consisting of quinoa and sweet potatoes. It took about 20 hours to make it  into ketosis in that first 24 hour fasting session. For the last three 24-hour fasts, I switched to a pre-fasting meal with a much lower percentage of carbohydrates. My meal consisted of chicken breast over a bed of spinach and cauliflower rice. This put me in ketosis quicker – at 16 hours into my fast versus 20 hours. In the future, I will keep my carbohydrate intake for that pre-fasting meal at 20% or lower of my macro breakdown, which for me at a 600 calorie meal works out to be about 26 g of carbohydrates. 

I didn’t notice much difference in hunger pangs, sleep, or energy levels between the different macro breakdowns of my pre-fasting meal. I’m guessing since I maintained a fairly consistent breakdown for the rest of my day, adjusting the make-up of one meal didn’t make much of a difference for fatigue or hunger.

Exercise might have helped me reach ketosis faster

My second fast was the only one I didn’t perform vigorous exercise about 12 hours into the fast, and my ketosis levels were slightly lower in the second fast than the others. Since I didn’t change anything else between fasts 2, 3, and 4, it might mean that exercise helps elevate my ketone levels. 

My favorite blood devices were Keto-Mojo and Precision Xtra. Biosense was the easiest-to-use breath device

In general, I felt the blood devices were more consistent compared to breath devices, but they were much less fun to use. Since we had to take a reading from each device 5 times during a 24-hour fast, my finger was definitely tired of getting pricked by the end of the day! If I were to invest in a device and was only using it occasionally, I prefer the Keto-Mojo or Precision Xtra. They gave fairly consistent readings, and they take both a glucose and ketone reading, rather than just ketones. This allows me to check in on my blood sugar levels as well. Too low, and I could start having issues thinking or functioning normally. Too high, and I might be at risk for long term issues with insulin resistance. 

If I were checking my ketosis level on a more regular basis or multiple times a day, I’d invest in a Biosense device. Even though it was the most expensive device, it was the easiest to use of the breath devices. I think some of my initial consistency issues with the breath devices were related to the learning curve for how to breathe into the device. Acetone is a ketone found in breath, and its concentration is highest at the end of the exhale. I had to learn to measure at the end of my breath to get a consistent reading between fasts. 

I appreciated the chance to participate in this study because I was able to learn more about how my body reacts to different pre-fast meals, as well as exercise, during a longer fast. Doing it with a group gave me a chance to compare and contrast different experiences, and it confirmed that every body reacts differently. I definitely recommend measuring ketone and glucose levels alongside food intake and exercise data leading up to and throughout longer fasts to understand more about what optimizes a fast for you.