Sunday, August 19, 2007

Intermittent Fasting and Exercise

I've written about intermittent fasting before. It is becoming quite a fashionable thing in some corners of the interweb, but there is a reason for that - there is a chunk of scientific data indicating that there are many benefits to be had from this approach to eating, from improved body composition to reduced inflammation.

I've just come across this paper to be published next month in Metabolism that adds a little more to the mix of data. It is looking at rats....but the assumption is that there is a similar effect in humans.

Basically fasting made the fat cells shrink. Refeeding normally makes them grow back to where they were. But if you add exercise to the mix then the fat cells do not go all the way back to where they were. The paper explains how this is due both to an increase in lipolysis (fat burning) and a decrease in lipogensis (fat making).

So what, how do we apply this? Well fasting and intermittent fasting is all well and good but I'd argue that you really need to add exercise to the mix if you are going to optimise the effect.

Exercise before or after refeeding prevents refeeding-induced recovery of cell size after fasting with a different pattern of metabolic gene expressions in rat epididymal adipocytes.

We investigated the effect of exercise before or after refeeding on cell size and on the expression of several messenger RNAs (mRNAs) involved in lipolysis and lipogenesis in fasted rat epididymal adipocytes.

Fasting for 65 hours reduced the diameter of adipocytes to 72.0 mum from 78.4 mum in fed control rats, whereas refeeding for 1 or 2 days restored adipocyte size to 74.0 or 75.8 mum, respectively.

Exercise before or after refeeding blocked refeeding-induced restoration of adipocyte size and led to adipocyte size similar to that observed after fasting.

Fasting dramatically reduced expression of the fatty acid synthase mRNA, although expression of this gene returned to the control level after refeeding. However, exercise after but not before refeeding inhibited recovery of the expression of fatty acid synthase mRNA resulting from refeeding. In contrast, exercise before but not after refeeding led to enhanced expression of mRNAs encoding the hormone-sensitive lipase and beta(3)-aderenoceptor.

Thus, exercise before or after refeeding prevents refeeding-induced restoration of adipocyte size after fasting via different pathways. Exercise before and after refeeding enhanced the expression of lipolytic mRNAs or inhibited the expression of lipogenic mRNAs, respectively.

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