Intermittent Fasting or Calorie Restriction?

Last week, Dr. Michael Mosley presented Horizon: Eat, Fast and Live Longer on the BBC. This entertaining special focused on intermittent fasting, a popular form of dieting for many people. Intermittent fasting is often confused with calorie restriction, which is the only proven dietary way to increase lifespan.  We were delighted to see the personable Dr.  Mosley host this program since he always does a good job of getting audiences to think about ways to improve health.

In the Power of Intermittent Fasting, an an article from BBC News Health, August 4 2012l,The BBC points out that the world record for extending life expectancy is held by a mouse that had been genetically engineered to produce very low levels of IGF1, a growth hormone that we frequently write about on  Genetically engineered mice live an extra 40%, which would be equivalent to a human making it to 120 years or more. For humans to lower IGF1, they must limit calories  and make sure that dietary protein is not excessive – right along with the RDA guidelines will do.

Intermittent Fasting

Intermittent fasting is usually defined as eating whatever you want on one day and then eating very little or nothing the next day. This eating pattern It is also called “alternate day fasting.”

Horizon: Eat, Fast and Live Longer focused on a study by Dr. Krista Varady of the University of Illinois at Chicago, who carried out a trial of alternate day fasting on groups of overweight humans. Here’s the full paper.  It showed that intermittent fasting was a successful means of weight loss.

Dr. Mosley admitted honestly that limiting calories would be difficult for him, but the idea of intermittent fasting seemed easier to do.  The intermittent fasting method he opted for was a 5:2 method, which means that a person would eat ad lib  for five days a week and for two days, he, as a male, would eat only 600 calories. Women would eat 500 calories.

We welcome the BBC’s drawing attention to this method of dieting as to a viable method of losing weight. Whether it works to lengthen lifespan and gain the extraordinary health benefits of calorie restriction (CR) is questionable. The Varady study looked at overweight people on a diet. In the Materials and Methods section of the paper, the details of the diet were not given. So we know little about whether it was put together in a way that would be likely to reproduce the cell signaling that is associated with longer life through CR.

The BBC points out that limiting growth is necessary for successful calorie restriction, but the method of CR that Dr. Mosley chose was shown not to limit growth in this study:

Dose effects of modified alternate-day fasting regimens on in vivo cell proliferation and plasma insulin-like growth factor-1 in mice.

Varady KA, Roohk DJ, Hellerstein MK


Calorie Restriction has Advantages over Intermittent Fasting

Further, we wonder with the on-then-off day intermittent-fasting approach, how the body could possibly adjust. Normally calorie restriction produces greatly reduced insulin secretion. That could have dire consequences on days when a person eats anything they want, for lots of insulin would be necessary to process a full meal.  With serious calorie restriction, the thyroid gets involved too by lowering its output of T3, which slows anabolic processes throughout the body. How would that work if you are eating a lot of calories on most days and very few on others? Can the thyroid, pancreas, heart, and many other organs that positively adapt to calorie restriction, be turned on and off like  machines? What evidence supports this?

The whole premise that intermittent fasting is easier is blind to the CR Way approach to happy dieting, which increases levels of feel-good biochemistry, like the neurotransmitter serotonin, in the brain. Serotonin-producing-meals are included in all CR Way diet plans for  calorie restriction.  Once happiness biochemistry is in place, low calorie living is easy and fun. People often say they no longer need their comfort foods to make it through the day.

But whatever method of CR you choose, take advantage of the friendly, supportive community at Living the CR Way with friends and input from experts will make a big difference in your success. Register to enjoy a free Healthy Start membership.


One Response to “Intermittent Fasting or Calorie Restriction?”

  1. heinz

    I have been doing both for 49 yrs (now 83)and can say that C.R. has some advantage. The best thing is to combine the two. Ever since Oct. 1964 I skip breakfast and this has resulted fine for me. Heinz.


Leave a Reply

Your email address will not be published. Required fields are marked *

* :

* :

* :