The Effects of Adaptation to a Low Carbohydrate/high Fat Diet and Pre-Exercise Feeding on Exercise Endurance, Metabolism, and Cardiovascular Dynamics in Swine

Abstract

By.• Av.,,jt) Ty (' If'S SAv A i or ist J SummaryField combat personnel may be required to sustain moderate intensity work loads for extended periods, while having to eat-on-the-run.The use of of a low carbohydrate (7% of calories)!high fat (74% of calories) diet (LCD) has been suggested as a means of improving endurance during moderate intensity exercise.Little is known about the interactions between preexercise eating and its effects on mechanisms of cardiovascular and metabolic control. A series of experiments were performed to establish a basis for manipulation of the metabolic system to improve exercise performance.yix groups of sedentary and exercise trained miniature swine were utilized to determine the effects of. preexercise feeding and adaptation to!a LCD on metabolism, moderate intensity exercise endurance, and cardiovascular dynamics. Data analysis has revealed important relationships between metabolic and cardiovascular control mechanisms. LCD adapted pigs ran an average 58 minutes longer than Control pigs when exercised at 65% of their heart rate reserve (moderate intensity exercise) and for up to 5 hours during tests. LCD pigs had higher blood glucose and lower blood lactate values than Control pigs at rest and during the runs to exhaustion.These data suggest a decreased utilization of carbohydrate as a fuel at rest and during exercise. Long term LCD adaptation (5 to 14 months) /resulted in no increases in either blood triglycerides or cholesterol and no health or growth problems, suggesting no deleterious health effects. LCD adaptation also produced a decrease in insulin sensitivity indicating a possible application in treatment of hypoglycemic syndrome.Preexercise feeding resulted in reduced skeletal and cardiac muscle blood flows at identical exercise intensities in spite of an increased cardiac output needed for the digestive process. The finding of reduced myocardial blood flow, accompanying the increased blood flow demands for the digestive processes' during exercise has implications related to the occurence of postprandial angina in man. The interactions between adaptation to a LCD and preexercise eating have pcteritial application to enhancing performance of combat personnel. The interrelationships among these and other variables are briefly discussed.-2