It’s basic diet math: Take in more calories than you burn, and you’ll gain weight. But startling new research on blood oranges suggests the ruby-red citrus might bend that equation in dieters’ favor.

Though results need to be confirmed with human trials, Italian researchers found that mice who drank the juice of blood oranges with their standard diet ended up 13% lighter at the end of three months. Other mice were fed a very high-fat diet complimented by either tap water, blood orange juice, regular orange juice or an anthocyanin extract. As expected, the fat-fed mice got fat — gaining as much as 23% in body weight — EXCEPT for the blood orange mice, who gained no weight at all!

Some previous research suggests the blood orange anthocyanin C3G (also found in strawberries, blueberries, raspberries and red grapes) deserves the credit, by enhancing fat burning and calorie conversion. Yet fat-fed mice on the anthocyanin extract still gained some weight — yet more evidence that the  whole food is always better than the sum of its parts. For example, blood oranges are also high in fiber, which can triple weight loss, and pectin fiber in particular, which helps dieters feel more full. Blood oranges are also high in  vitamin C, which may contribute to metabolism, during exercise.

Bonus:  Blood oranges may have benefits beyond weight loss. High citrus consumption was linked to a 50% lower risk of cancers of the mouth, throat and stomach, in one study.

Published March 1, 2010