An increased mobilization of the hepatic glycogen is necessary for the maintenance of glucose homeostasis during exercise. To examine the effect of exercise on glucose metabolism when the hepatic glycogen stores are depleted, five prolonged-fasted (60-h, PF) subjects were investigated. Arterial concentrations and splanchnic exchange of glucose and… Read More

Lean healthy individuals are characterized by the ability to rapidly adapt metabolism to acute changes in substrate availability and metabolic rate. However, in glucose-intolerance/insulin-resistant conditions, such as that induced by starvation, the flexibility of tissues to rapidly respond to change in substrate availability is diminished. We asked whether the conundrum of increased glucose… Read More

This study examines the effects of a 2-h exercise of moderate intensity (50% of VO2 max) on the tracer-determined turnover rate of ketone bodies (KB) in 21 normal subjects fasted for 16 h, 5 days, whose basal ketonemia ranged between 0.09 and 6.16 mM. The KB response observed at the end of exercise is a function of the initial degree of ketosis. When basal… Read More

Eight healthy men (17–31 yr) were studied in the postabsorptive state(control) and after a 59-h fast. They had venous blood drawn at rest and during 10 min of moderate work (treadmill running requiring 60% of the individual maximal oxygen uptake) succeeded by 5 min of heavy work (requiring 100% of the individual maximal oxygen uptake). Fasting resulted in a halving of insulin concentrations, a… Read More

Catecholamines have multiple metabolic and fluid-electrolyte as well as cardiovascular effects, and their levels in plasma respond to alterations in nutrient and sodium intakes. Plasma norepinephrine, epinephrine, and dopamine were measured in 12 obese nondiabetic subjects before and after 400 kcal/day diets of either protein or glucose, followed by total fasting, and then by hypocaloric… Read More

The concentration of ketone bodies and their rate of transport (estimated with an infusion of beta-[14C]-hydroxybutyrate) were determined before, during, and after exercise in overnight-fasted and 3- to 5-day-fasted subjects who walked on a treadmill for 2 h at approximately 50% of their VO2max. In overnight-fasted subjects, exercise increased the rate of… Read More

Exhaustive graded exercise leads to changes of hormones, carbohydrate, and lipid metabolism in normal controls and obese patients after prolonged starvation. Concomitant with a large increase of plasma catecholamines, insulin concentration is reduced and blood glucose levels slowly increase. More glucose is made available by glycogenolysis and gluconeogenesis than can be… Read More

Energy expenditure and the circulating concentration of various intermediary metabolites, insulin and glucagon, were measured in five lean subjects at rest and during a 20-min period of a standardized exercise (50-75 watts). Measurements were made before starvation, at the end of a 4-d period of total starvation and 24-32 h after refeeding. The respiratory quotient decreased… Read More

A 38-hr fast was used as a provocative test in patients suspected of having defects in muscle substrate utilization. In five controls and nine patients, exercise capacity and respiratory exchange ratio were determined before and at the end of the fast. Blood was collected at intervals during the fast from ten controls and nine patients for creatine kinase (CK), free fatty… Read More