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Contact: Donna Krupa
dkrupa@the-aps.org
301-634-7209
American Physiological Society
What you eat after exercise matters
BETHESDA, Md. (Jan. 28, 2010) — Many of the health benefits of aerobic
exercise are due to the most recent exercise session (rather than weeks,
months and even years of exercise training), and the nature of these
benefits can be greatly affected by the food we eat afterwards,
according to a study published in the Journal of Applied Physiology
(
http://jap.physiology.org).
"Differences in what you eat after exercise produce different effects on
the body's metabolism," said the study's senior author, Jeffrey F.
Horowitz of the University of Michigan. This study follows up on several
previous studies that demonstrate that many health benefits of exercise
are transient: one exercise session produces benefits to the body that
taper off, generally within hours or a few days.
"Many of the improvements in metabolic health associated with exercise
stem largely from the most recent session of exercise, rather than from
an increase in 'fitness' per se," Dr. Horowitz said. "But exercise
doesn't occur in a vacuum, and it is very important to look at both the
effects of exercise and what you're eating after exercise."
****************Specifically, the study found that exercise enhanced
insulin sensitivity, particularly when meals eaten after the exercise
session contained relatively low carbohydrate content. *************8
Enhanced insulin sensitivity means that it is easier for the body to
take up sugar from the blood stream into tissues like muscles, where it
can be stored or used as fuel. Impaired insulin sensitivity (i.e.,
"insulin resistance") is a hallmark of Type II diabetes, as well as
being a major risk factor for other chronic diseases, such as heart disease.
Interestingly, when the research subjects in this study ate relatively
low-calorie meals after exercise, this did not improve insulin
sensitivity any more than when they ate enough calories to match what
they expended during exercise. This suggests that you don't have to
starve yourself after exercise to still reap some of the important
health benefits.
The paper, "Energy deficit after exercise augments lipid mobilization
but does not contribute to the exercise-induced increase in insulin
sensitivity," appears in the online edition of the journal. The authors
are Sean A. Newsom, Simon Schenk, Kristin M. Thomas, Matthew P. Harber,
Nicolas D. Knuth, Haila Goldenberg and Dr. Horowitz. All are at the
University of Michigan. The American Physiological Society (APS:
www.the-aps.org) published the research.
Study Design
The study included nine healthy sedentary men, all around 28-30 years
old. They spent four separate sessions in the Michigan Clinical Research
Unit in the University of Michigan Hospital. Each session lasted for
approximately 29 hours. They fasted overnight before attending each
session, which began in the morning.
The four hospital visits differed primarily by the meals eaten after
exercise. The following describes the four different visits:
They did not exercise and ate meals to match their daily calorie
expenditure. This was the control trial.
They exercised for approximately 90 min at moderate intensity, and then
ate meals that matched their caloric expenditure. The carbohydrate, fat,
and protein content of these meals were also appropriately balanced to
match their expenditure.
They exercised for approximately 90 min at moderate intensity and then
ate meals with relatively low carbohydrate content, but they ate enough
total calories to match their calorie expenditure. This
reduced-carbohydrate meal contained about 200 grams of carbohydrate,
less than half the carbohydrate content of the balanced meal.
They exercised for approximately 90 min at moderate intensity and then
ate relatively low-calorie meals, that is, meals that provided less
energy than was expended (about one-third fewer calories than the meals
in the other two exercise trials). These meals contained a relatively
high carbohydrate content to replace the carbohydrate "burned" during
exercise.
The exercise was performed on a stationary bicycle and a treadmill. The
order in which the participants did the trials was randomized.
In the three exercise trials, there was a trend for an increase in
insulin sensitivity. However, when participants ate less carbohydrate
after exercise, this enhanced insulin sensitivity significantly more.
Although weight loss is important for improving metabolic health in
overweight and obese people, these results suggests that people can
still reap some important health benefits from exercise without
undereating or losing weight, Dr. Horowitz said.
The study also reinforces the growing body of evidence that each
exercise session can affect the body's physiology and also that
differences in what you eat after exercise can produce different
physiological changes.
Next Steps
The research team is now performing experiments with obese people, aimed
at better identifying the minimum amount of exercise that will still
improve insulin sensitivity at least into the next day.
###
Editor's Notes: To arrange an interview with Dr. Horowitz, please
contact Donna Krupa (301) 634-7209 or at
dkrupa@the-aps.org.
Funding: The National Institutes of Health
Physiology is the study of how molecules, cells, tissues and organs
function to create health or disease. The American Physiological Society
(APS) has been an integral part of this scientific discovery process
since it was established in 1887.
Eating low carb after exercise best for improving insulin sensitivityeven without weight loss 
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