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发帖数: 29846 | 1 http://www.functional-fitness-facts.com/starvation-diets.html
In his book Burn The Fat, Feed The Muscle, fat loss expert Tom Venuto
explains why starvation diets don't work. I want to share with you five of
his reasons why they don't work.
1. Very low calorie diets slow down your metabolic rate.
The first thing that occurs during a severe calorie shortage is a decrease
in your metabolic rate. The lower your calories, the slower your metabolism
becomes. This metabolic slowdown is well documented. When calories are
restricted, your metabolism decreases by at least 20-30%. With severe
calorie restriction, some studies have shown that resting metabolism can
become depressed by as much as 45%! This is why, after prolonged low calorie
dieting, you can eat very little food and still not lose weight. This also
explains why it is so difficult to lose those last 10 or 20 pounds.
2. Very low calorie diets make you lose muscle.
The most devastating effect of a very low calorie diet is the loss of muscle
tissue. Once the starvation alarm is triggered, your body begins looking
for ways to conserve energy. Muscle is metabolically active tissue. Getting
rid of it is the body's way of decreasing energy expenditure. It's easy for
your body to use muscle for energy. This process is known as gluconeogenesis
- converting muscle into glucose. This includes skeletal muscles, internal
organs, and even your heart muscle!
Study after study has shown that very low calorie diets without exercise
will always cause 40-50% of the weight loss to come from muscle. Many
starvation diets, especially those that are very low in carbohydrates, cause
large losses in water weight. Between the loss of water, glycogen and
muscle, fully 75% of the weight you lose on many starvation diets is not fat
! The initial weight loss on most starvation diets is very deceiving, giving
you only the illusion of success. Even with exercise, if a diet is too
restrictive, much of the weight loss will still be muscle.
3. Very low calorie diets increase the activity of fat-storing enzymes.
The chief fat storing enzyme is called Lipoprotein Lipase (LPL). When you
drop your calories too low, your body will produce more LPL and less fat
burning enzymes. In other words, when you don't eat enough, your body
changes its chemistry to make it easier to store fat in the future.
4. Very low calorie diets decrease output of thyroid hormone.
The thyroid gland is largely responsible for the regulation of your basal
metabolic rate (the rate at which you burn calories at rest). When your body
senses a severe reduction in calories, there is a corresponding reduction
in the output of active thyroid hormone (T3). The result is a decrease in
your metabolic rate and fewer calories burned.
5. Very Low calorie diets increase the chance of rebound weight gain.
Almost everyone loses weight initially on a very low calorie diet, but it
never takes long before the body catches on and starts conserving energy.
That's when you hit a plateau. Once you hit the plateau, it becomes much
harder to keep losing weight, even if your calories are extremely low. This
lack of continued results, combined with gnawing hunger pangs and insatiable
cravings, usually causes people to give up out of sheer frustration. They
go off their diet, the weight creeps back on, and their body fat ends up
back where they started - only now they have less muscle and a slower
metabolism.
With a slower metabolism, what used to be a maintenance level of calories
now becomes a surplus, and the weight comes right back on. Most people gain
back all the weight they lost - and some gain back even more, leaving them
fatter than when they started. This up and down pattern of weight loss and
weight regain is commonly known as the "yo-yo cycle," and it often continues
for years or even for an entire lifetime. With each repeated bout of
dieting, your metabolism becomes less and less efficient and you can
actually become progressively fatter while eating less food.
As you can see, starvation diets don't work. If you want to learn what does
work when it comes to losing weight, check out Tom's Burn The Fat, Feed The
Muscle program. |
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