LONDON, April 19 An Imperial College London canine study suggests a calorie-restricted diet might result in extended longevity.In the study led by Jeremy Nicholson, Labrador retriever dogs fed a calorie-restricted diet showed different lifelong patterns relating to energy metabolism and the activities of their gut microbes. The dogs lived nearly two years longer than similar dogs given a slightly higher-calorie diet.Nicholson and colleagues from Nestle Purina Research centers in Switzerland and the United States noted previous studies also established calorie restriction as a proven method for extending the lifespan of animals. But that research did not explain how calorie restriction works.The new study suggests some beneficial changes might relate to the activities of symbiotic bacteria that live in the intestinal tract. Those microbes, the scientists said, produce a range of biochemicals that might influence disease processes and alter energy metabolism in host organisms.Researchers said although their goal was to help develop diets that keep pets alive and healthy for as long as possible, the findings might also be relevant to human dietary changes and obesity.The study is scheduled for the May 4 issue of the Journal of Proteome Research.Copyright 2007 by UPI