After only six days of enough treadmill exercise to burn 500 kilocalories (k/cal) each day, the eight subjects in the negative energy balance (NEG) group, who received no energy replacement, showed a significant (p=0.037) 40% increase in insulin action (measured by glucose rate of disappearance/steady state insulin). However insulin action was unchanged in the zero energy balance group (ZERO), who were required to finish a sports drink during exercise and additional food afterward to "replace" the 500 k/cal.
The same subjects showed positive trends in both traditional and novel CVD risk factors, though not at a significant level. On the other hand, the subjects in the ZERO group showed either virtually no change or bad changes in CVD risk factors.
Both studies were performed on the same groups by Steven E. Black (a doctoral student) and Elizabeth Mitchell (an undergraduate honors student), both working in the laboratory of Barry Braun in the Department of Exercise Science, University of Massachusetts, Amherst. Black will present, "Improved insulin action following short-term exercise training: effects of exercise or energy balance?" while Mitchell will present "The effects of short-term exercise, in negative or zero energy balance, on CVD risk factors."
Editors note: Mitchell, Black and Braun are speaking at the American Physiological Society's 2004 Intersociety Meeting, "The Integrative Biology o