Non-communicable diseases (NCDs), including cancer, cardiovascular disease, and type 2 diabetes, account for roughly three-quarters of deaths worldwide, and their global burden is expected to continue increasing over the coming decades.
Growing evidence suggests that many of these conditions share a common feature: mitochondrial dysfunction. Mitochondria are the energy-producing structures inside cells. When they do not function efficiently, cells may not meet their energy demands, triggering a cascade of oxidative stress, cellular damage, and inflammation across tissues.
As such, mitochondria may serve as a barometer of cellular health. When they function well, they help protect cells. But when their function declines, they may contribute to the processes that lead to chronic disease.
Now, a research review suggests that a simple finger-prick blood test that measures the balance between glucose and ketones could offer a new way to monitor metabolic health in people with chronic conditions.
Published in Frontiers in Science, the authors propose that the glucose ketone index (GKI) could provide clinicians with a practical tool for assessing metabolic status and tracking how well lifestyle interventions such as diet, fasting, and exercise improve metabolic health.
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The glucose ketone index (GKI) is a biomarker that measures the ratio of blood glucose to β-hydroxybutyrate, the primary ketone the body produces during nutritional ketosis. The test requires only a finger-prick blood sample and was originally developed to monitor adherence to ketogenic diets in cancer research.
Generally, lower GKI values indicate lower blood glucose and higher ketone availability, reflecting ketosis. This state has been associated with improved mitochondrial energy production and may help reduce metabolic processes linked to chronic disease.
Conversely, higher GKI values reflect higher glucose and lower ketone availability, which may indicate less efficient mitochondrial metabolism.
As such, the researchers propose that GKI could monitor how individuals respond to evidence-based lifestyle interventions aimed at improving metabolic health.
These approaches may include ketogenic dietary changes, fasting, and regular physical activity, all of which may shift metabolism toward nutritional ketosis.
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Therefore, the GKI could offer a pathway to support the prevention and management of cancer and chronic disease.
Lead author Thomas Seyfried, PhD, from Boston College, U.S., explained to Medical News Today why the GKI may provide a more meaningful measure of metabolic health than traditional markers.
“The GKI, which computes the ratio of glucose to the ketone body beta-hydroxybutyrate in blood, is a more stable biomarker for predicting systemic metabolic homeostasis than is glucose measurement alone,” he explained.
“Consistent with the information presented in our paper are the findings from the recent KetoSAge trial showing that the presence of a safe, elevated level of ketone bodies in the blood (euketonaemia) was associated with improved insulin sensitivity, liver function, and reduced pro-inflammatory and growth-related biomarkers,” he said.
“On the other hand, higher GKI values indicated excessive insulin release, with worsening biomarker profiles despite seemingly normal glucose ranges. We therefore believe that the GKI has the potential to become a clinically useful, non-invasive biomarker that reflects whole-body metabolic endocrine physiology more comprehensively than either blood glucose or body weight measurements.”
— Thomas Seyfried, PhD
However, the authors emphasize that ketogenic therapies should be viewed as one possible management strategy under appropriate clinical supervision, rather than as cures for chronic illnesses.
“Cellular mitochondrial dysfunction is a major factor underlying most major cancers and many chronic diseases,” lead author Derek Lee, PhD, also from Boston College, told MNT. “We propose that the GKI can be used as a simple, quantitative blood biomarker for predicting mitochondrial health.”
“We show that high GKI values are linked to increased disease risk while low GKI values are linked to reduced risk. This knowledge can empower individuals to make nutrition and lifestyle choices that can help protect or enhance the energetic efficiency of their mitochondria, thus improving their general health status.”
— Derek Lee, PhD
Although the researchers believe the GKI shows promise, they stress that the test is not intended to diagnose or cure disease, and they acknowledge that important questions remain unanswered before it can be widely adopted in routine care.
Large clinical studies will be required to determine whether GKI values reliably predict disease risk, treatment response, or long-term outcomes across different conditions.
Researchers must also establish appropriate target ranges for individual diseases and determine how much time patients should spend within those ranges to achieve meaningful benefits.
The authors highlight the association between mitochondrial dysfunction and many chronic illnesses and conclude that the GKI could become a useful tool for monitoring metabolic health.
They suggest that combining GKI with evidence-based strategies, such as nutrition and exercise, could provide a framework for monitoring health and inform efforts to address the substantial health burden of NCDs. Importantly, GKI testing could offer clinicians and patients a clearer measure of metabolic health than weight alone.
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The researchers call for future studies to report glucose, ketone, and GKI measurements more consistently, as well as additional biomarkers such as insulin, triglycerides, and inflammatory markers. They propose that standardized reporting could make it easier to compare findings between studies and better understand how changes in the GKI relate to broader metabolic health.
“It is important to emphasize that achieving a low GKI is not a simple task for most people initially,” concluded co-author Isabella Cooper, PhD, from the University of Westminster, UK. “A gradual start is essential with slow macronutrient changes, prioritizing electrolytes and hydration, and using the GKI to track your progress rather than relying on guesswork.”
“It is a remarkable learning experience to see how nutrition and lifestyle changes can change your systemic metabolism. Many people start to see and feel benefits after a few weeks. However, people should always consult with a medical professional if they are inexperienced or unsure about the process.”
— Isabella Cooper, PhD
For now, the findings suggest that GKI is a promising research tool that may eventually help clinicians monitor metabolic changes and personalize lifestyle interventions, rather than as a validated clinical test for managing cancer or other chronic diseases.
