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Exercising In The Heat Helps You Eat
Less
Exercisers trying to cut down on calories might want to take
a run in the sun instead of a climate-controlled gym, according
to a small Australian study.
The study of 11 physically active men found
that participants ate less immediately after working out in hot
conditions -- about 97 degrees Fahrenheit (36 Celsius) -- than
in a more moderate, 77 degree Fahrenheit (25 degrees Celsius)
environment.
On average, the men ate roughly 300 calories more when they worked
out in moderate temperatures than when they exercised in the heat.
"Our findings suggest that if you exercise in a warmer environment
you will eat less in the subsequent meal," researcher Dr.
Kym Guelfi, of the University of Western Australia's School of
Sports Science, told Reuters Health.
One type of "hot" exercise is Bikram or hot yoga, which
is a series of yoga poses done in a very heated room, which is
usually maintained at a temperature of 105 degrees Fahrenheit
(approximately 40 degrees Celsius). Yoga at this temperature promotes
profuse sweating, which is believed to help rid the body of toxins.
Besides the benefits on appetite, it also keeps the body very
warm and, therefore, more flexible.
In theory, she said, that would be a good strategy for exercisers
trying to lose weight. However, Guelfi added, future studies should
look at whether warm-weather exercisers just make up for the smaller
meals with larger ones later in the day.
For the study, which is published in the American Journal of
Clinical Nutrition, the researchers had 11 young, regularly active
men make several visits to the exercise lab.
During one visit, the men ran on a treadmill for 40 minutes in
97 degree heat; on another visit, they performed the same workout
under 77 degree conditions. On a third visit, they rested in a
moderately warm room.
In all three situations, the men were then presented with an
all-you-can-eat breakfast buffet and were found to eat the most
after working out in moderate conditions.
The study also found clues as to why exercising in the heat may
dull appetite. After the hot workout, the men typically showed
higher blood levels of peptide YY, a hormone produced in the digestive
tract that serves a "fullness" signal.
The men's smaller appetites also appeared to be related to the
increases in core body temperature that came with the hot workouts.
The reasons for this are not clear, but Guelfi noted that some
researchers believe that, because eating produces heat in the
body, food intake is one of our natural mechanisms for controlling
body temperature.
"This is why, anecdotally, cold environments have been said
to lead to an increase in appetite," she said.
But while a warmer environment may help curb post-exercise appetites,
Guelfi cautioned against taking that idea to extremes. "Exercise
should not be performed in overly hot environments due to the
risk of dehydration and heat illness," she said.
Another plus is an increase to your metabolic rate. Exercising
in a warmer environment consistently may raise your long-term
metabolic rate. People living in tropical environments generally
have BMR's
5-20% higher than those living in more temperate climates.
Reference
Source 202, 226
November 18, 2009
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