Fasting cholesterol
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The Impact of Fasting on Cholesterol Levels: A Comprehensive Review
Introduction to Fasting and Cholesterol
Fasting, whether intermittent or prolonged, has been widely studied for its potential health benefits, including its effects on cholesterol levels. Cholesterol, a crucial lipid in the body, is often measured in terms of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG). This article synthesizes findings from multiple studies to provide a clear understanding of how different fasting regimens impact cholesterol levels.
Intermittent Fasting and Cholesterol Levels
Effects on Total Cholesterol and LDL-C
Intermittent fasting (IF) has been shown to significantly reduce total cholesterol and LDL-C levels. A systematic review and meta-analysis found that both IF and energy-restricted diets (ERD) led to significant reductions in TC and LDL-C compared to non-diet controls. Specifically, the weighted mean difference (WMD) for TC was -6.93 mg/dL, and for LDL-C, it was -6.16 mg/dL, indicating a notable improvement in these lipid parameters.
HDL-C and Triglycerides
The same meta-analysis reported that IF and ERD did not significantly affect HDL-C levels but did result in a modest reduction in triglycerides (WMD, -6.46 mg/dL). Another study focusing on a once-per-week water-only fasting regimen found no significant change in LDL-C levels but did observe improvements in insulin resistance, suggesting potential benefits for other cardiometabolic risk factors.
Prolonged Fasting and Cholesterol Levels
Increases in LDL-C and Total Cholesterol
Contrary to intermittent fasting, prolonged fasting can lead to increases in LDL-C and total cholesterol. A study involving a 7-day fast in healthy, non-obese adults found significant increases in both total cholesterol (37.3%) and LDL-C (66.1%). This increase was associated with weight loss and a decrease in insulin-like growth factor-I (IGF-I) levels.
Cholesterol Esterification and Lipoprotein Changes
A 10-day modified fast in patients with rheumatoid arthritis showed a reduction in total cholesterol and phospholipids in plasma, primarily due to a decrease in the low-density lipoprotein fraction. However, the high-density lipoprotein fraction remained unchanged, and the rate of cholesterol esterification, which reflects the turnover of cholesteryl esters in plasma, was reduced.
Alternate Day Fasting and Exercise
Combined Effects on Cholesterol Metabolism
A pilot randomized controlled trial investigated the combined effects of alternate day fasting (ADF) and exercise on cholesterol metabolism. The study found that exercise, with or without ADF, significantly improved cholesterol metabolism as measured by serum sterol signatures, which are markers of cholesterol absorption and biosynthesis. Increased physical activity had a greater effect on cholesterol biosynthesis than weight reduction or calorie restriction alone.
Non-Fasting vs. Fasting Lipid Profiles
Clinical Implications
Recent evidence suggests that fasting is not routinely required for lipid profile determination. Non-fasting lipid profiles have been shown to be comparable to fasting profiles in predicting cardiovascular disease. This has significant clinical implications, as it simplifies the process for patients and may improve compliance with lipid testing.
Conclusion
Fasting, whether intermittent or prolonged, has varying effects on cholesterol levels. Intermittent fasting generally leads to reductions in total cholesterol and LDL-C, with minimal impact on HDL-C and triglycerides. In contrast, prolonged fasting can increase LDL-C and total cholesterol levels. Combining fasting with exercise may enhance cholesterol metabolism, and non-fasting lipid profiles are now considered reliable for clinical use. These findings highlight the complexity of fasting's impact on cholesterol and underscore the need for personalized dietary recommendations.
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