Insulin levels fasting
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Fasting Insulin Levels: Insights and Implications
Decline in Insulin Levels During Fasting
Fasting has a significant impact on insulin levels. Research involving children undergoing diagnostic fasting studies revealed that insulin levels decline markedly during fasting periods. Initial insulin levels averaged 7.4 mU/ml, which dropped to 1.4 mU/ml by the end of the fasting period 1. This decline in insulin is accompanied by a rise in IGF-binding protein-1 (IGFBP-1), suggesting a regulatory mechanism where IGFBP-1 increases as insulin decreases, potentially to counteract hypoglycemia by modulating IGF activity 1.
Impact of Fasting and Energy-Restricting Diets on Insulin
Systematic reviews and meta-analyses of randomized controlled trials have shown that fasting and energy-restricting diets lead to significant reductions in fasting blood sugar (FBS), insulin, and insulin resistance (HOMA-IR) levels. Specifically, fasting or energy-restricting diets resulted in a weighted mean difference (WMD) of -1.288 μU/ml in insulin levels 2. These findings underscore the potential of dietary interventions in managing insulin levels and improving metabolic health.
Insulin Levels and Metabolic Health
Fasting insulin levels are not only indicative of current metabolic status but also predictive of future health risks. Higher fasting insulin concentrations have been associated with an increased risk of hypertension and coronary heart disease (CHD). A meta-analysis of prospective cohort studies found that each 50-pmol/L increment in fasting insulin was linked to a 25% increase in hypertension risk and a 16% increase in CHD risk 4. This highlights the importance of monitoring fasting insulin as a marker for potential cardiovascular issues.
Genetic Influences on Fasting Insulin
Genetic studies have identified several loci associated with fasting insulin and insulin resistance. For instance, loci near IGF1 have been linked to fasting insulin and HOMA-IR, indicating a genetic predisposition to variations in insulin levels and metabolic function 5. These genetic insights can help in understanding individual differences in insulin regulation and the risk of developing type 2 diabetes.
Insulin and Leptin Relationship
Research has shown that fasting insulin levels can influence plasma leptin levels independently of adiposity. In both cross-sectional and intervention studies, a significant positive association was found between fasting insulin and leptin levels. Even after weight loss, changes in insulin levels were significant predictors of changes in leptin levels, suggesting that insulin plays a role in regulating leptin beyond just reflecting fat stores 6.
Intermittent Fasting and Insulin Sensitivity
Intermittent fasting has been shown to improve insulin sensitivity. A study involving healthy men subjected to intermittent fasting every second day for 15 days demonstrated an increase in insulin-mediated glucose uptake rates and a more pronounced insulin-induced inhibition of adipose tissue lipolysis 7. These findings support the concept that intermittent fasting can enhance metabolic function and insulin action.
Insulin Levels in Pre-Diabetes
In individuals with pre-diabetes, there is a positive correlation between fasting blood sugar and fasting insulin levels. This relationship emphasizes the role of insulin resistance in the progression to type 2 diabetes and highlights the need for early intervention to manage insulin levels and prevent the onset of diabetes 8.
Conclusion
Fasting insulin levels provide critical insights into metabolic health and the risk of developing chronic diseases. The decline in insulin during fasting, the impact of dietary interventions, genetic influences, and the relationship with other metabolic markers like leptin and glucose underscore the multifaceted role of insulin in health and disease. Monitoring and managing fasting insulin levels can be a key strategy in preventing and treating metabolic disorders.
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Most relevant research papers on this topic
Free and total insulin-like growth factor (IGF)-I levels decline during fasting: relationships with insulin and IGF-binding protein-1.
Free and total IGF-I levels decline steadily during fasting, likely due to the steady rise in IGFBP-1, which serves to protect against potential insulin-like activity of IGFs during fasting.
Observational Study
Highly CitedThe effect of fasting and energy restricting diets on markers of glucose and insulin controls: a systematic review and meta-analysis of randomized controlled trials
Fasting or energy-restricting diets significantly reduce fasting blood sugars, insulin, and HOMA-IR levels, but have modest, non-significant effects on HbA1c levels.
Meta-AnalysisJoint analysis of fasting and postprandial plasma glucose and insulin concentrations in Venezuelan women.
Venezuelan women with impaired glucose metabolism can be categorized into prediabetics and diabetics, allowing more specific treatment and predicting metabolic disorder progression.
Observational StudyFasting insulin concentrations and incidence of hypertension, stroke, and coronary heart disease: a meta-analysis of prospective cohort studies.
Higher fasting insulin concentrations are significantly associated with an increased risk of hypertension and coronary heart disease, but not stroke, suggesting early fasting insulin ascertainment may help identify those at high risk of cardiovascular disease.
Meta-Analysis
Very Rigorous JournalNew genetic loci implicated in fasting glucose homeostasis and their impact on type 2 diabetes risk
New genetic loci have been identified influencing fasting glucose and type 2 diabetes risk, highlighting the potential of genetic studies of glycemic traits to identify risk factors and modest elevations in glucose levels.
Meta-Analysis
Rigorous JournalHighly CitedFasting insulin levels influence plasma leptin levels independently from the contribution of adiposity: evidence from both a cross-sectional and an intervention study.
Fasting insulin levels significantly influence leptin levels, even during weight loss, beyond the impact of total adiposity.
RCTHighly CitedEffect of intermittent fasting and refeeding on insulin action in healthy men.
Intermittent fasting increases insulin-mediated glucose uptake rates in healthy men, supporting the thrifty gene concept and supporting the need for periodic feast and famine cycles in modern society.
Non-RCTHighly CitedAssociation of fasting glucose and fasting insulin levels: Insights into the mechanisms of pre-diabetes
A positive correlation exists between fasting blood sugar and fasting insulin levels in individuals with pre-diabetes, emphasizing the need for early intervention and tailored strategies to address insulin resistance.
Higher fasting plasma free fatty acid levels are associated with lower insulin secretion in children and adults and a higher incidence of type 2 diabetes.
Higher fasting free fatty acid levels are associated with lower insulin secretion in children and adults with normal glucose tolerance and a higher risk of impaired glucose tolerance and type 2 diabetes.
Observational StudyHighly CitedHow good a marker is insulin level for insulin resistance?
In population studies, only fasting insulin levels should be used as a marker of insulin resistance, particularly in subjects with abnormal glucose tolerance.
Observational StudyHighly Cited