People strictly following the U. S. Department of Agriculture's famous "Food Pyramid" would eat 2,000 to 2,500 calories a day -- hundreds fewer than many Americans actually consume.
A man on a severely calorie-restricted diet would have a 40 percent reduction in total calories, to about 1,500 per day, according to the American Federation for Aging Research. Most of those calories would come from fruits and vegetables.
Such a diet usually means weight loss -- to the point of looking ill. Adherents often feel cold and are constantly hungry. They lose so much body fat that walking and sitting can hurt because they have so little tissue cushioning their hips and the soles of their feet. Digestive system upsets often occur, as well.
Few people could sustain the diet for their entire lives. Some have tried, as evidenced by the popularity of books like, "The 120 Year Diet," by Dr. Roy Walford of the University of California at Los Angeles.
Intermittent fasting, in contrast, means hunger and discomfort only every other day. Adherents would consume only water or other non-caloric fluids on fast days.
They might even be able to gorge on alternate days, making up for lost calories, and still get all the benefits. Lab mice in the National Institutes of Health studies did just that, and still showed beneficial effects.
Intermittent fasting should not be confused with serious eating disorders like anorexia or bulimia, which drive people to eat fewer calories than their bodies need in order to look thin.
Michael Woods can be reached at mwoods@nationalpress.com or 1-202-662-7072.
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