In a study that is bad news for adherents of the Atkins Diet and health-food advocates, most of the benefits of caloric restriction were found to be due to reduction of fats and proteins. The study, though, used fruit flies as subjects, so there is no proof yet that the same effect holds for mammals, particularly humans.

Also Read: Preventive Healthcare and Health Insurance

In the study, the fruit flies were divided up into four groups. Group #1 received a regular diet -- yeast and sugar. Group #2 was calories restricted, about 43% of the calories in the unrestricted diet, consisting of equal parts yeast and sugar. Groups #3 and #4 received more calories, about 72% of the unrestricted diet, with #3 getting more yeast than sugar, while #4 had more sugar than yeast.

The flies in group #2, on the typical caloric restriction diet, lived 82% longer than those in Group #1, as would be expected. Group #4 lived 65% longer than #1, but group #3 only lived 9% longer than group #1.

Stated another way, reducing caloric intake by 28% through reducing fat and protein intake increased life expectancy substantially, but reducing caloric intake by 28% through reducing sugar intake had only a slight beneficial effect.

Personally, I don't understand why the second group was not given the same amount of calories as groups three and four, it would have made the comparison more valid. Flies living on mostly sugar received 79% of the benefit (compared to only 11% for the flies eating mostly yeast) but they only reduced caloric intake by roughly half as much as group #2.

I'd be surprised if these findings extend to mammals. Of course we will have to wait some time to find out, since studies of mammals, which live several years (compared to fruit-flies that live several weeks) naturally take longer. Here at Longevity Blog we hope somebody is preparing a more thorough study of lab rats, with diets high in fats only, high in protein only, and high in sugars only, compared to both unrestricted and a control group getting the same calories as the study groups.