Intermittent fasting and leptin

12 Jan

Re previous post: have done a little reading that may explain it – yay for being a woman!

Many people get super hung up on insulin and don’t think about leptin – which was only discovered in 1994 and influences appetite, among other things.

Martin Berkhan of Leangains says:

“Intermittent fasting and leptin

Generally speaking, studies show a neutral effect on average leptin levels during intermittent fasting. While the fasting period decreases circulating leptin, this is compensated by a big boost when refeeding. In comparison to conventional meal frequencies, intermittent fasting induces a “peak and valley”-pattern in leptin synthesis. Leptin secretion is thus entrained to the meal pattern and shifting meal timing causes a comparable shift in plasma leptin rhythm.

However, there are some interesting discrepancies here in that women actually show a big increase in mean leptin levels during intermittent fasting. This occurs even in the absence of weight gain which is all the more fascinating. In the quoted study, despite calorie intake being elevated in comparison to baseline intake, the women actually lost weight and lowered waist circumference and body fat percentage. Intermittent fasting was also shown to decrease neuropeptide-Y, a hormone that stimulates hunger. This could probably be explained by elevated leptin levels, but there was no linear correlation between the two in this case.

Similar effects have also been shown to occur in men. That is, fat loss occurred without any reduction in leptin – and these were fairly lean athletes to begin with.

Intermittent fasting may also be of benefit when dieting in the single digit range due to the effect of fasting on the fat mobilizing hormones epinephrine and norepinephrine. When you’re in the single digit body fat range, you’re likely to have low circulating levels of leptin. One of leptin’s downstream effects is on epinephrine and norepinephrine output. Low leptin equals impaired output of the aforementioned hormones. This is part of how leptin regulates metabolic rate. However, it seems that these hormones increase regardless during fasting. That is, leptin is not able to exert it’s usual power over these hormones. In this case, their increase cannot be mediated by leptin which allows fat mobilization to go on unabated during fasting.”

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