One recent trend that has received a significant amount of attention,
both in the online blogosphere and in traditional fitness media, is the
idea of performing exercise first thing in the morning on an empty
stomach. The practice of exercising in a “fasted state” has been
promoted as a way to burn more calories from fat than from
carbohydrates, making it an effective way to boost the fat-burning
effects of exercise.
There are a couple of theories on why doing cardio in a fasted state first thing in the morning may be more effective for fat burning. For example, cortisol is a hormone that helps promote the metabolism
of fat for energy. One theory suggests that, because cortisol levels
are higher in the morning, exercising on an empty stomach will lead to
greater amounts of fat burning. A second theory posits that, because the
body’s resting metabolism continues to work overnight while the body
sleeps, lower levels of carbohydrates will be available for fuel before
breakfast. As a result, the body will have to rely on fats as the
primary energy source for any physical activity.
Research exists to support both theories. For example, studies have
shown that fasted exercise can help endurance athletes burn higher
levels of fat than carbohydrates. However, while there may be some
benefit to exercising on an empty stomach, here are three specific
reasons why fasted exercise may not a good choice over the long-term.
- Exercise in a fasted state could burn more calories from fat, but it
also could cause the body to burn protein for fuel, which would reduce
the amount that can be used to help repair and build muscle tissue.
Gluconeogenesis is the process of converting proteins to glucose for
energy. In short, if carbohydrates (glycogen in muscle and liver,
glucose in the blood stream) are not immediately available for energy,
the body can convert proteins for fuel, which leaves fewer proteins
available to rebuild muscle post-exercise.
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- The body has plenty of free fatty acids (FFAs) available for
exercise. The FFAs that are not immediately converted to energy to fuel
muscle activity can be redeposited in adipose tissue in the abdominal
region. In other words, they will end up as belly fat. Exercising when
cortisol levels are higher could lead to more FFAs circulating in the
blood than can be used. So, rather than depleting levels of fat,
exercise first thing in the morning could actually shift body fat to the
abdominal region.
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- If the goal is weight loss by metabolizing as much fat as possible,
it is more important to consider energy expenditure over a 24-hour
period and not just at one point during the day. Monitoring energy
intake and expenditure throughout the day and identifying how to reduce
excessive intake and increase opportunities to move can play a more
significant role in long-term weight loss than trying to burn more fat
by exercising first thing in the morning.
While it doesn’t offer a viable long-term solution, exercising in a
fasted state could be a SHORT-TERM technique for helping a client
achieve a specific body-composition goal. Here are three things to
consider about using fasted exercise:
- For years, bodybuilders and figure competitors have utilized fasted
exercise to help reduce body fat prior to a competition. This is because
low-intensity, steady-state (LISS) exercise below the first ventilatory
threshold will rely on FFAs as the primary fuel source. To be most
effective for fat burning, exercise in a fasted state should focus on
LISS, where the intensity is low enough to allow the client to talk
comfortably during exercise. Exercise at higher intensities will
metabolize more carbohydrates and require more oxygen; therefore, the
rate of breathing will increase to bring in more oxygen and exhale more
carbon dioxide, which will make talking difficult.
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- The body is an extremely adaptable organism. If the same exercise is
performed at the same intensity for an extended period of time, the
body will become very efficient at producing energy to fuel the
activity. Doing fasted exercise first thing in the morning could help a
client move past a sticking point, but after a period of time the body
will adjust to this condition. That’s the signal that it’s time to
change the workout.
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- A client may like to exercise first thing in the morning and simply
prefer doing so on an empty stomach. If this is the case, help them
maximize energy metabolism by recommending LISS over higher-intensity
exercise protocols. If a client wants to participate in high-intensity
exercise first thing in the morning, it is important that he or she know
how to properly fuel after the workout.
It’s important to note that eating a meal or snack too soon before
exercise can raise the levels of insulin, which helps metabolize and
store fat. If insulin is elevated prior to exercise, the result could be
fewer FFAs available for energy. A low-glycemic snack more than 30
minutes prior to exercise can provide energy for a workout and reduce the risk of elevating insulin levels.
Finally, keep in mind that substrate utilization for producing the
energy required to fuel workouts is regulated by a number of variables,
including hormone levels, available nutrition substrates, enzyme
activity and the intensity, duration and type of physical activity.
Exercise in a fasted state could provide some short-term benefits, but
the downside is that it could also limit the amount of protein available
for muscle building. It’s more important to help clients identify ways
to be more active throughout the day and guide them toward healthier
nutrition choices than it is to recommend working out at a specific time
of day.
Source ACE :
Pete McCall
Health and Fitness Expert
