Mechanisms of Intermittent Fasting Unveiled

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Intermittent fasting (IF) is proven to have beneficial effects on aging, cancer, cardiovascular diseases and neurodegenerative diseases. However, it isn’t known whether the benefits of IF are due to caloric restriction (CR), as with fasting, or whether they’re due to changes in eating pattern. Recent studies have discovered that the browning of white fat can improve insulin sensitivity and energy expenditure by producing heat. Both exercise and cold exposure have been shown to transform white fat into brown fat.

A recent study by Kim et al. from the University of Toronto looked into the mechanisms underlying intermittent fasting’s effects on health. They separated mice into 2 groups: an IF group and a control group. The IF group was not fed for 1 day and then fed for 2 days in a row whereas the control group was fed daily. This went on for 4 months. By the end of the study, both groups had been fed the same amount of calories. After 4 months, the IF mice weighed significantly less and had increased insulin sensitivity and a more stable glucose metabolism. Additionally, they had a lower proportion of white fat because it had been converted into brown fat. The IF mice had higher levels of adipose vascular endothelial growth factor (VEGF). VEGF helps form new blood vessels and activates adipose macrophages (white blood cells) which are critical for the browning of white fat and heat production. Interestingly, IF led to the browning of visceral white fat while cold exposure leads to the browning of subcutaneous white fat.

The authors note that health is not solely about “what and how much” we eat but also “when and how often”.