PROTEIN SPARING ON VERY-LOW-CALORIE DIETS - GROUND-SQUIRRELS SUCCEED WHERE OBESE PEOPLE FAIL

During seasonal cycles in ground squirrels, as in many other species, there are periods of spontaneous loss of appetite, very low calorie in take and a 30% loss in body mass. Measurements of nitrogen balance dur ing early and later stages of the mass loss phase of the cycle (-1.2 /- 6.7 and +13.1 +/- 8.8 mg/24 h, respectively) showed a total sparing of protein, indicating a selective use of fat. However, when no food at ail was available, nitrogen balance was negative (-45 +/- 5 mg/24 h ). Provided that they have access to some food, ground squirrels are t herefore able to compensate for any protein utilization, while at the same time selectively losing large amounts of fat. It appears that a f actor related to spontaneous reduction in food intake enables these an imals to achieve the total sparing of protein that eludes dieting huma ns on comparably low caloric intakes.