The Impact of Intermittent Fasting on Insulin Resistance: A Review of Current Literature
Intermittent fasting (IF) is a dietary pattern that involves alternating periods of fasting and eating. This dietary approach has gained popularity in recent years due to its purported health benefits, including improved metabolic health and reduced risk of chronic diseases. One potential benefit of IF is its impact on insulin resistance, a condition in which the body's cells become resistant to the effects of insulin, leading to elevated blood glucose levels and a higher risk of developing type 2 diabetes. In this article, we will review the current literature on the impact of intermittent fasting on insulin resistance.
Insulin resistance is a complex condition that involves a variety of factors, including genetics, lifestyle, and diet. One of the key contributors to insulin resistance is the accumulation of excess body fat, particularly around the abdominal region. This type of fat, known as visceral adipose tissue, produces a variety of inflammatory cytokines that can interfere with insulin signaling and promote insulin resistance.
One of the ways in which intermittent fasting may improve insulin resistance is by promoting weight loss and reducing visceral adipose tissue. Studies have shown that IF can lead to significant weight loss, particularly when combined with a healthy diet and regular exercise. A meta-analysis of 27 studies found that IF was associated with a significant reduction in body weight, body mass index (BMI), and waist circumference, all of which are risk factors for insulin resistance (1).
In addition to promoting weight loss, IF has been shown to improve insulin sensitivity, which is the ability of the body's cells to respond to insulin. Several studies have found that IF can improve insulin sensitivity in both healthy individuals and those with type 2 diabetes. A study of 10 healthy men found that a 16-hour fast led to a significant improvement in insulin sensitivity compared to a normal eating pattern (2). Another study of individuals with type 2 diabetes found that a 24-hour fast led to a significant improvement in insulin sensitivity, as well as a reduction in fasting glucose levels (3).
One of the mechanisms by which IF may improve insulin resistance is through its effects on the gut microbiome. The gut microbiome is a complex ecosystem of microorganisms that play a critical role in metabolism and immune function. Studies have shown that IF can alter the composition of the gut microbiome, leading to an increase in beneficial bacteria and a reduction in harmful bacteria. This shift in the microbiome may contribute to the improvements in insulin sensitivity seen with IF (4).
Another potential mechanism by which IF may improve insulin resistance is through its effects on oxidative stress and inflammation. Both oxidative stress and inflammation have been implicated in the development of insulin resistance and type 2 diabetes. Studies have shown that IF can reduce oxidative stress and inflammation, which may help to improve insulin sensitivity (5).
In conclusion, the current literature suggests that intermittent fasting may have a positive impact on insulin resistance. IF may promote weight loss, improve insulin sensitivity, alter the gut microbiome, and reduce oxidative stress and inflammation. While further research is needed to fully understand the mechanisms by which IF improves insulin resistance and the optimal fasting protocols for different populations, IF appears to be a promising dietary strategy for improving metabolic health and reducing the risk of chronic diseases.
References:
Harris L, Hamilton S, Azevedo LB, et al. Intermittent fasting interventions for the treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Database System Rev Implement Rep. 2018;16(2):507-547. doi:10.11124/JBISRIR-2017-003985
Tinsley GM, La Bounty PM. Effects of intermittent fasting on body composition and clinical health markers in humans. Nutr Rev. 2015;73(10):661-674. doi:10.1093/nutrit/nu
Halberg N, Henriksen M, Soderhamn N, et al. Effect of intermittent fasting and refeeding on insulin action in healthy men. J Appl Physiol. 2005;99(6):2128-2136. doi:10.1152/japplphysiol.00683.2005
Liang H, Ren H, Luo M, et al. The alterations of gut microbiota in mice with chronic intermittent fasting intervention. BioMed Res Int. 2019;2019:1301420. doi:10.1155/2019/1301420
Johnson JB, Summer W, Cutler RG, et al. Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radic Biol Med. 2007;42(5):665-674. doi:10.1016/j.freeradbiomed.2006.12.005