Eating a diet that is high in fat and low in carbs has become widely popular in the past few years, and for good reasons. When our body is burning fat for energy, it produces ketones as a byproduct.

Metabolic flexibility is the body’s ability to easily switch between fuel sources. Ketone burning may have several health benefits, including reducing inflammation and promoting longevity, according to research.

Here we look at why metabolic flexibility matters and how you can use a combination of ketone and glucose monitoring to help build your metabolic flexibility.


The body releases fat from stores in the form of free fatty acids to be used as fuel. Many tissues in the body can use free fatty acids for energy, but some tissues, like the brain, cannot.

When free fatty acids are released, your body also starts to produce ketones. These can be used as an alternative fuel by the brain and other tissues, such as the heart and muscles.

The release of fat from storage and the increase in FFA concentration leads to an increase in ketone concentration. If your body is producing ketones, it means that it is burning fat for energy rather than glucose.

But why should you care about raising your ketones? There are several benefits to having elevated ketones in your body, including weight loss, a better body composition (more muscle and less fat), and improved metabolism.

If you use fat as your primary source of fuel instead of glucose, you are less likely to be obese.

The ketones produced when following a ketogenic diet have anti-inflammatory properties which can help to reverse damage caused by conditions such as chronically high blood sugar.

Scientists have discovered that the keto diet may be good for more than just weight loss. There is also evidence that suggests that the keto diet may help protect against inflammatory diseases such as Alzheimer’s.

Third, increased levels of ketones in the body may help to reduce oxidative stress, which can lead to increased health and a longer life span. Fourth, the presence of ketones in your blood signifies that your body is engaging metabolic pathways that utilize fat for energy and exhibiting metabolic flexibility.

How to Measure Ketones

We are discussing three different ketone compounds: acetoacetate (AcAc), beta-hydroxybutyrate (BHB), and acetone.

AcAc is the product of the breakdown of fatty acids by the body, while BHB is made from AcAc and acetone is a side product of that process.

There are three ways to test ketone levels at home: through the blood, breath, or urine. Testing your blood for BHB is accurate, but it is also expensive and requires a finger prick.

Urine tests for ketone levels can lose accuracy the longer a person is in a state of ketosis.

Breath monitoring is the most convenient method for detecting acetone, which is exhaled in the breath and is a direct derivative of AcAc.

Blood or urine ketone measurements are typically in millimoles per liter (mmol/L), and readings can be anywhere from 0 to 6. If you want to see a level of 0.5 mmol/L to know that your body is burning ketones, you should test your blood ketone levels.

The concentration of ketones in one’s breath can be indicated in parts per million (ppm) or in clinical grade ACEs (a proprietary unit from Readout Health). Ketone concentrations can range from 0 to 40 Aces. If you have 2 ppm or 5 ACEs in your system, you’re likely in ketosis.

This can give you a more realistic gauge for the efficiency of fat burning, versus relying on urinary ketones where the absolute BHB levels may look higher since you are not in a fasted state. Since ketones are quickly used for fuel by our cells during a fast, measuring BHB levels in our breath may give us a more accurate gauge of fat-burning than measuring ketone levels in our urine, which can show higher levels of ketones even when we’re not in a fasting state.

If you exercise, you’ll see that your blood ketones go down, because you’re using them for energy. But your breath ketones will go up because that’s a better reflection of ketones that come from fat. Measuring your ability to burn fat is a way to gauge your metabolism’s flexibility.

What You Can Learn from Monitoring Glucose and Ketones Together

Ketone and glucose monitoring are two important aspects of managing one’s metabolism. If our glucose levels are stable, we can be confident that our insulin levels are not being stimulated and fat burning is more likely to occur.

We can check if this is happening by looking at the ketone monitor. We can check if our ketone levels are rising as expected by checking our glucose monitor. If we see a rise in glucose levels, it may be due to the release of insulin, which would inhibit fat burning.

Best Uses for Ketone Monitoring and CGM Together

1. Weight Loss/Intermittent Fasting

One great way to control your blood sugar and ketone levels is during intermittent fasting (IF). If you want to lose weight, you should eat less often. This will give your body time to use up the glucose you eat and convert to burning fat for energy.

The biggest challenge is determining whether your food choices and the length of your fasting period are putting you into a fat-burning state.

CGM can help you see if you are maintaining stable glucose levels during your feeding period, which is important to avoid excess glucose in your system during your fasting period. Ketone monitoring can help you see if IF is leading to increased fat burning.

If you use these technologies together, you can create a personalized intermittent fasting regimen that works best for you. For example, you might find that switching from carbs to protein lowers your blood sugar and the amount of time it takes to start burning fat.

2. Carb-Cycling

Wearing a CGM and monitoring ketone levels can also be helpful for people following a carb-cycling or refeeding diet.

There are specific eating regimens that will help you burn carbohydrates during exercise, especially if the workout is long or hard. Following these regimens will also help increase your metabolism of fat.

CGM can show you how your food choices affect your blood sugar levels, so you can see what your body can use for energy on days when you are working out hard. Ketone monitoring on lighter days can help you see if you are fat burning.

CGM and ketone data can help you build a carb-cycling protocol that works for you.

CGM data and ketone data can provide a detailed view of what fuel your body is using and how much of it is available in real-time, so you can adjust your diet and exercise accordingly to improve your body’s ability to use different fuels.

Get Started with Metabolic Flexibility

If you’re not sure how to assess and adapt your metabolic flexibility, here is a guide on how to get started:

1. Track Your Glucose

Active tracking is the best way to monitor glucose levels. There are no physical cues that indicate which foods will cause your blood sugar levels to rise and put a strain on your cells.

The only way to get information about your glucose levels in real-time is to use a continuous glucose monitor. The app lets you see which lifestyle influences and foods directly impact your glucose levels.

You can improve your metabolic health by making simple changes. The program also gives you the ability to customize your nutrition plan to find what works best for your body.

Tracking your glucose levels provides data that directly shows how any lifestyle changes affect your body.

2. Focus on Your Diet

Diet always affects your metabolic flexibility. Remember the phrase, “you can’t outrun a bad diet.”

A poor diet can offset the benefits of exercise. The best way to improve your diet is to eat more whole foods and avoid processed foods.

• Avoid the Standard American Diet

The average American diet contains too much sodium, refined grains, processed vegetable oils, and added sugars. About half of American adults have chronic diseases that could be prevented.

To improve your body’s ability to burn fat, focus on eating whole foods and minimizing your intake of sugar and refined carbs.

Lowering your carbohydrate intake helps to:

  • Reduce your glucose and insulin levels
  • Put less stress on your cells
  • Improve metabolism
  • Improve metabolic health

• Try cyclical ketosis

If you are considering making changes to your diet or starting a new diet, then cyclical ketosis may be a good option for you.

A meal plan that involves following a ketogenic diet most of the week, but adding in periods where you eat more carbs.

The standard keto diet is a low-carb, high-fat diet. A standard keto diet generally contains very few carbohydrates. Adding in more carbohydrates causes your body to go in and out of ketosis. Going through this process enables your body to burn both glucose and fat for energy, making it more metabolically flexible.

The perfect cyclical keto diet is very personal. Some people do best when they have a meal with more carbohydrates once a day as part of their routine. Some people do better by including one high-carb day per week in their diet.

The best way to find your ideal blood sugar level is to use a CGM so that you can assess in real-time how your body responds.

• Eat within your energy requirements

If you eat too much food, it can make you unable to move easily. Extra calories lead to blood sugar levels rising too high, which leads to the body becoming resistant to insulin and storing fat.

Eating within your energy requirements reduces the risk of obesity and improves metabolic flexibility.

3. Get Enough Exercise

This means that your body isn’t able to use the energy from the food you eat very well. Exercise helps to control glucose levels, which is key in fighting diabetes.

Exercise has been shown to increase the number of mitochondria in cells, improve blood sugar control, and make cells more sensitive to insulin. Having better insulin sensitivity means that your body can better regulate blood sugar levels.

If you want to improve your metabolism, mix up your workouts. Different types of exercises will make your body more flexible and better at burning calories.

Any type of exercise is beneficial. However, experts generally agree that the best results are achieved by combining aerobic cardio with strength training.

Zone 2 training helps the mitochondria work better while strength training makes it easier for the body to control blood sugar levels.

Muscle activation through exercise is often recommended as a preventative measure against developing metabolic diseases.

4. Intermittent Fasting

When you eat is just as important as what you eat when it comes to metabolism.

Intermittent fasting can help improve your body’s insulin resistance and make it more metabolically flexible. Fasting lowers insulin levels, which causes your body to burn ketones for energy.

Research identifies that intermittent fasting has several other benefits, as it:

If you are looking for a way to improve your metabolism without affecting your lean muscle mass, intermittent fasting is a well-researched solution.

5. Get Enough Rest and Repair (stress and sleep management)

There is a lot of clinical research on the connection between sleep, stress, and metabolic health.

Not getting enough sleep can cause serious long-term health problems like diabetes and heart disease. The amount and quality of sleep you get are both important for keeping your metabolism healthy.

Not getting enough sleep can make it harder for your body to process sugar, which can lead to health problems like diabetes.

In fact, poor sleep can:

  • Affect hormone levels (lowering leptin increasing ghrelin)
  • Increase inflammation in the body
  • Promote insulin resistance
  • Cause chronic health problems
  • Increase weight gain

Good sleep habits are essential for improving your body’s ability to burn calories effectively. This is closely related to managing stress, which has a similar effect on your metabolism.

Stressful situations cause our bodies to release hormones like adrenaline and cortisol. When our bodies face a stress response of “fight or flight,” they release glucose to provide the extra energy required to deal with the situation.

If someone experiences chronic stress, their body will produce too much glucose on a regular basis. Prolonged exposure to high levels of glucose can result in the development of diabetes. If you want to improve your metabolism, reducing stress and getting enough sleep are two important steps you can take.


The close connection between glucose, metabolic flexibility, and metabolic health is evident. You don’t need to have diabetes to have high blood sugar levels, and high blood sugar levels lead to metabolic problems.

When the body is unable to switch fuel sources easily, it causes an increase in glucose levels. You need to monitor your glucose levels to develop a true understanding of your individual metabolic flexibility.


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About Rhoda ...

Rhoda is an award-winning dietitian, mature age model, and CEO of Sayvana Women.  

She is the creator of the Elegant Eating Solution, an affordable program that helps women avoid weight regain and feel great about themselves, without restrictive eating.

Elegant Eating is based on the science of protein leverage and follows the unique R.E.M.A.P approach to successful aging.

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