Wednesday, October 24, 2007

Fasting and Fat Loss

I spent the morning catching up on some reading today, and came across a very interesting study in Acta Physiologica Scandinavia - The journal of the Scandinavian physiological society. In this study the effects of a 3-day fast on regional lipid and glucose metabolism was examined.

The authors found the typical benefits that are associated with fasting:

  • No decrease in Energy Expenditure - metabolic rate DID NOT slow down

  • A decrease in RQ - indicating an increase in fat burning

  • Increased blood flow - some very impressive numbers, I challenge any "NO" supplement to show this kind of data!!

  • Decreased blood insulin levels - Considered to be one of the major health benefits of fasting

  • Increased glucagon levels - more reliance on body fat as a fuel source

  • Increased Growth Hormone levels - Anybody who has read Eat Stop Eat knows that I think this is one of the major keys behind the benefits of fasting

  • Increased noradrenaline - More fat burning hormones

  • No increase in cortisol - No reason to think that muscle is being broken down

One of the major things that caught my eye in this paper was the great graph showing the change in fuel sources that were fueling metabolism.

You'll notice that the amount of calories being burned are roughly the same (about 2000 Kcals), however during fasting a lot more of these calories are coming from fat. And, since the subjects were not eating any fat while fasting, this fat must have been body fat.

Another interesting finding was that the majority of this fat was either stomach fat or muscle fat.

While I would not recommend fasting for 3 days straight (I prefer 24 hours), this study does add evidence to the idea that fasting can be an effective method of reducing calorie intake, and does not negatively effect metabolic rate, or muscle mass.


(Gjedsted J, Gormsen LC, Nielsen S, et al. Effects of a 3-day fast on regional lipid and glucose metabolism in human skeletal muscle and adipose tissue. Acta Physiol 2007, 191, 205-216.)

To learn more about fasting for weight loss, you can check out Eat Stop Eat

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Denise said...

This is so cool, Brad. Using fasting for weight loss has been a blessing for me. Ever since reading Eat Stop Eat & applying fasting I have dropped one size & lost 10 pounds. In only 1 1/2 months. I'm almost at my goal weight which I haven't seen in about 2 years all while dieting & working out.

Brad Pilon said...

Hi Denise,

Thanks for the update!

It makes me so happy when I hear stories like yours.

keep me updated


Anonymous said...

i would not dismis the benfits of longer fasts. 8-21 days

Victor said...

It has been said that we can live for: 3 minutes without air; 3 days without water; and 3 months without food.

I've never tried: not breathing for 3 minutes; not drinking for 3 days; nor not eating for 3 months - but I have not eaten for 1 month (while drinking water every waking hour.)

For a couple of years I faster from Friday evening to Monday morning one day a month and am now fasting the occasional day.

I have read that, as I have had a coronary artery graft and have a tendency to have coronary artery blockages, that I should not fast. NOTE The heart problems started about 10 years and 20 kg after I stopped the fasting. Does anyone have an information about fasting or not with an heart condition?