From the Guidelines
Fasting has been shown to improve insulin sensitivity by allowing the body to reset its metabolic processes, with the most recent and highest quality study suggesting that early time-restricted feeding improves 24-hour glucose levels and affects markers of the circadian clock, aging, and autophagy in humans [@18@].
Key Findings
- The study by Sutton et al. found that early time-restricted feeding improves insulin sensitivity, blood pressure, and oxidative stress even without weight loss in men with prediabetes [@18@].
- Other studies have also shown that intermittent fasting regimens, such as time-restricted eating or alternate-day fasting, can enhance insulin sensitivity and provide metabolic benefits [1, @4@, @7@, @10@, @14@].
- Weight loss from fasting further improves insulin sensitivity, as excess body fat contributes to insulin resistance.
Practical Approaches
- Time-restricted eating (eating within an 8-10 hour window daily) is a practical approach for most people, as it allows for flexibility and can be adapted to individual lifestyles.
- Alternate-day fasting is another approach that has been shown to be effective, but may be more challenging for some individuals to adhere to.
Considerations for Diabetes
- For those with diabetes, fasting should be approached cautiously with medical supervision, as medication adjustments may be necessary to prevent hypoglycemia 1.
- The American Diabetes Association recommends adjusting medication doses and timing during fasting periods to minimize the risk of hypoglycemia and hyperglycemia 1.
Additional Tips
- Staying hydrated during fasting is essential, and breaking fasts with moderate-sized, balanced meals helps maintain the metabolic benefits.
- It is also important to listen to your body and adjust your fasting regimen as needed to avoid any adverse effects.
From the Research
Effect of Fasting on Insulin Sensitivity
- Fasting has been shown to have a positive effect on insulin sensitivity in people with type 2 diabetes, with studies suggesting that it can improve metabolic and cardiovascular markers, as well as body composition 2, 3.
- A network meta-analysis of 13 studies with a total of 867 patients found that twice-per-week fasting was the most effective intermittent fasting regimen for improving insulin sensitivity and reducing fasting blood glucose and glycated hemoglobin levels 2.
- A narrative review of studies on fasting in type 1 and type 2 diabetes mellitus found that fasting can increase insulin sensitivity, reduce endogenous glucose production, and improve fat metabolism, making it a potentially useful therapeutic approach for managing diabetes 3.
- However, not all studies have found a positive effect of fasting on insulin sensitivity, with one study finding that prolonged fasting induced peripheral insulin resistance in healthy lean subjects, which was not ameliorated by high-dose salicylate 4.
- Other studies have found that fasting can be an effective alternative to insulin therapy for people with type 2 diabetes, with one case series documenting three patients who were able to reverse their insulin resistance and cease insulin therapy through therapeutic fasting 5.
Comparison with Other Therapies
- A study comparing the effects of pioglitazone, metformin, and gliclazide on postload glycemia and composite insulin sensitivity index in patients with type 2 diabetes found that pioglitazone was more effective than metformin and gliclazide in improving insulin sensitivity 6.
- Another study found that pioglitazone plus metformin was more effective than gliclazide plus metformin in reducing postload glycemia and increasing composite insulin sensitivity index 6.
Limitations and Future Directions
- More clinical trials are needed to verify the effectiveness of fasting as a therapeutic approach for managing diabetes and to determine the optimal fasting regimen for improving insulin sensitivity 2, 3.
- Further research is also needed to understand the mechanisms by which fasting affects insulin sensitivity and to determine whether fasting is safe and effective for people with different types of diabetes and other health conditions 3, 4.