Running on One-Third Empty

Abstract

F ranz, a 17-year-old rhesus monkey, is busy moving hand to mouth, stuffing his cheek pouches full of the pellets of food that have just been poured into his feeder. In minutes, it's empty. Only then does he begin to chew, pausing occasionally to take a drink of water, play with the metal gizmos clipped to his cage, or bare his teeth in a mild threat to the strangers who today showed up with the chow. Across the room, Damion is having a more leisurely meal, picking through the pellets with pencil-thin fingers, occasionally dropping one out of reach. He really wastes a lot, says his caretaker. the morning feeding at the Wisconsin Regional Primate Research Center in Madison. Franz and Damion are among the 75 rhesus monkeys taking part in an extensive, longterm study designed to get to the crux of an astonishing physiological phenomenon: Substantial undernutrition without malnutrition keeps a body living longer and in better condition. For the past 8 years, Franz has been getting 30 percent less than the amount he'd take for himself; Damion has been getting about the amount he'd normally eat. Franz is also getting supplemental vitamins and minerals to prevent deficiencies. The diets differ only in total carbohydrates, proteins, and fats. Since rhesus monkeys in captivity live for 30 to 40 years, it will be a couple of decades before any life extension can be documented. Nevertheless, the animals -are now entering middle age, when ageand diet-related diseases start to crop up in humans and other primates. The two rhesus groups represented by Franz and Damion are beginning to diverge in health and physiology-in both predicted and unexpected ways. It's an important time, says Joseph W Kemnitz, one of the animal physiologists who started the Wisconsin study in 1989 with funding from the National Institute on Aging. Altogether, the NIA is spending an estimated $6.5 million annually to study the effects of calorie-restriction on about 250 primates, including groups