Fasting every other day cuts weight, ups crankiness

Shunning food every other day may be a feasible way to slash calories - if you and those around you don't mind the crankiness that comes with it, according to researchers.

Their study of 16 nonobese men and women looked at the effects of alternate-day fasting, an eating plan that interspersed fasting days with "feasting" days that allowed participants to eat as much as they wanted.

The researchers were interested in whether food deprivation every second day would be easier on people than counting calories on a daily basis, lead author Dr. Eric Ravussin told AMN Health.

They found that the diet plan was indeed "feasible," at least for the duration of the 3-week study. Overall, the men and women lost an average of 5 pounds, while shedding some body fat.

On the other hand, Ravussin said, "most people were not happy" - a major problem being the crankiness that erupted on the fasting days and did not abate over the 3 weeks.

Ravussin and his colleagues at the Pennington Biomedical Research Center in Baton Rouge, Louisiana, report the findings in the American Journal of Clinical Nutrition.

Uncovering the most tolerable ways for people to cut calories is not just a matter of trimming waistlines. A number of studies, Ravussin explained, have now shown that calorie restriction can extend the lives of everything from yeast and worms to rodents and, possibly, monkeys.

There are a number of theories on why limiting food might make for a longer, healthier life. One idea, Ravussin noted, is that slowing the rate of metabolism reduces the generation of oxygen free radicals, potentially cell-damaging molecules that are a normal byproduct of the metabolic process.

No one knows if calorie counting can extend human life as it does for some animals. Ravussin and his colleagues are currently conducting a trial, sponsored by the National Institutes of Health, which is examining how long-term dietary restriction affects people's health and longevity.

Studying dietary restriction in people is, of course, far more complicated than studying it in lab rats. The ongoing trial is investigating how calorie cutting affects "biomarkers of longevity" in people, such as levels of blood sugar and insulin, a hormone key in regulating blood sugar.

The trial is testing several methods of dietary restriction - from pure calorie cutting to burning extra calories through exercise - to see which are most viable.

In the current study, Ravussin's team evaluated the effects of alternate-day fasting, an approach not included in that trial. They wanted to see if the eating plan was feasible and whether it influenced biomarkers of longevity, as well as participants' weight and metabolism.

As mentioned, every other day for 3 weeks the men and women subsisted on calorie-free beverages and sugarless gum. On the days in between, they ate whatever they wanted.