|
Does the cold weather make it harder to get in shape? Now that winter is well and truly here, we've had a few questions from
people wanting to know whether the cold weather makes it harder to get
in shape. This depends, of course, on where you live. What you're about to read
assumes that it gets colder and darker in the winter, and lighter and
hotter in the summer (i.e. Toronto!). There's plenty of research to show that your body will respond very differently
to the same program of diet and exercise in the summer than it does in
the winter. Here's why... Firstly, the temperature in which you exercise affects the number of
fat calories your body burns for energy. Some evidence for this comes
from a trial published in the Medicine and Science in Sports and Exercise.
Male subjects cycled for 90 minutes in several different temperatures. ~ Minus 10 degrees Celsius The number of fat calories burned for energy was reduced at both minus
10 degrees Celsius and 20 degrees Celsius compared with 10 degrees. Previous
research at Kent State University also shows an increase in protein breakdown
when you exercise in the cold. This is not the only study to look at the effect of cold air on fat metabolism.
And the results are far from conclusive. In fact, during submaximal exercise
in the cold, fat metabolism has been reported to be elevated, unchanged
or reduced. Other studies have combined whole body precooling before the exercise.
This can reduce core body temperature, leading to a "shivering"
response. It might explain why some trials show that the cold actually
increases the amount of fat burned for energy. In this study, the normal rise in core temperature associated with exercise
stopped the subjects from shivering. This is why we think it's more relevant
to people who exercise regularly. Skin temperature also affects growth hormone levels. In fact, simply
taking a hot (38-39 degrees Celsius) bath for 25 minutes will raise growth
hormone levels more than ten-fold. A single surge in growth hormone increases both the number of fat calories
your body burns for energy and your metabolic rate. That's why growth
hormone therapy often leads to a reduction in fat mass. Hibernating animals (those that sleep during the winter) tend to store
fat before they hibernate. One of the ways they accomplish this is via
an increase in the activity of enzymes (such as lipoprotein lipase, known
also as LPL) that promote the storage of fat. More interesting still, LPL levels in humans also rise and fall in tandem
with the seasons. Winter also sees a change in the activity of several fat-burning hormones. For example, cortisol levels reach a low point in the summer. Not only
is cortisol associated with the storage of abdominal fat, it's also been
linked to all kinds of health problems, including diabetes, heart disease
and depression. Cortisol may also weaken your immune system, leaving you
more susceptible to colds and flu. There's also evidence to show that you'll find it harder to control your
appetite in the winter rather than the summer. Some studies, for instance,
show a link between the "winter blues" and a drop in serotonin
levels. Serotonin is a chemical that helps messages pass from one nerve cell
to another. It helps different parts of your brain "talk" to
each other. When serotonin drops below a certain level, your brain "thinks"
that your body is starving and "tells" you to start eating.
In fact, some researchers believe that there's direct link between obesity
(due to overeating) and decreased brain serotonin levels. Overweight people with low levels of serotonin feel almost compelled
to eat more. Once they get their carbohydrate "fix", serotonin
levels rise, and they feel better again - albeit temporarily. Dr Albert Stunkard, a professor of psychiatry at the University of Pennsylvania,
thinks that people with an almost uncontrollable urge to raid the fridge
late at night are doing it to help themselves sleep by boosting serotonin
levels. In other words, some people who suffer from the "winter blues"
may use foods high in carbohydrate to make themselves feel better. The bottom line is that many people will find it harder to get in shape in the winter rather than the summer. This is normal. During the winter months, it's perfectly reasonable to expect a slower rate of fat loss and muscle gain. Keep this in mind if you've made any New Year's resolutions this year. next article |