Fasting glucose levels and health
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Fasting Glucose Levels and Health Outcomes
Fasting Glucose and Mortality Risk
Research shows a J-shaped relationship between fasting glucose levels and all-cause mortality, meaning both low and high fasting glucose levels are linked to higher death rates. The lowest mortality risk is seen in fasting glucose levels between 80–94 mg/dL in the general population, and 110–124 mg/dL in older adults with diabetes. Prediabetes (100–125 mg/dL) is associated with higher mortality, and the risk is especially pronounced in younger adults and those with multiple health conditions. Very low fasting glucose (<95 mg/dL) can also increase cardiovascular risk in older adults with multiple comorbidities 157.
Fasting Glucose and Cardiovascular Disease
Even fasting glucose levels within the high-normal range (95–99 mg/dL) are linked to an increased risk of cardiovascular disease (CVD) compared to lower levels (<80 mg/dL), even in people without diabetes. This risk remains after accounting for other factors like age, blood pressure, and cholesterol. Thus, fasting glucose can help identify healthy individuals at higher risk for CVD before they develop prediabetes or diabetes .
Fasting Glucose and Type 2 Diabetes Risk
Higher fasting glucose levels within the normal range (87 mg/dL and above) independently predict a greater risk of developing type 2 diabetes, especially when combined with high triglycerides or higher body mass index (BMI). This means that even people with “normal” fasting glucose can be at increased risk for diabetes if their levels are at the higher end of the normal spectrum .
Fasting Glucose and Cancer Risk
High fasting glucose is associated with an increased risk of certain cancers, such as gastric cancer, particularly in postmenopausal women and non-smokers. Additionally, diabetes-level fasting glucose is linked to higher cancer mortality 79.
Effects of Intermittent Fasting on Fasting Glucose and Metabolic Health
Intermittent fasting (IF) can lower fasting glucose, improve insulin sensitivity, and reduce body weight and waist circumference in people with metabolic syndrome or type 2 diabetes. IF also leads to better postprandial (after eating) glucose control and less glucose variability. These benefits are seen in both short-term pilot studies and larger meta-analyses, suggesting IF may be a useful tool for improving glucose metabolism and reducing chronic disease risk 4810.
Prolonged Fasting and Glucose Metabolism
Longer fasting periods (such as 36 hours) improve insulin sensitivity in both non-obese and obese individuals, as well as those with type 2 diabetes. However, non-obese people may experience higher glucose variations and a reduced early insulin response after prolonged fasting, while obese and diabetic individuals show a more stable response .
Conclusion
Fasting glucose levels are a strong indicator of health risks, including mortality, cardiovascular disease, type 2 diabetes, and certain cancers. Both high and low fasting glucose levels can be harmful, with the lowest risk generally found in the mid-normal range. Intermittent fasting and meal timing strategies can help improve fasting glucose and overall metabolic health, especially in those at risk for diabetes or with metabolic syndrome. Monitoring fasting glucose, even within the normal range, is important for early identification and prevention of chronic diseases.
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