Sunday, August 3, 2008 by Dr. Manny
The Medifast diet allows you to lose weight quickly. Medifast diet products utilize a high protein to carb ratio to help you do this. Even with Medifast diet products, you will have a difficult time losing weight if your thyroid function is not correctly balanced.
Thyroid Functions and Weight Loss
What is the relationship between thyroid and weight?
It has been appreciated for a very long time that there is a complex
relationship between thyroid disease, body weight and metabolism.
Thyroid hormone regulates metabolism in both animals and humans.
Metabolism is determined by measuring the amount of oxygen used
by the body over a specific amount of time. If the measurement is made
at rest, it is known as the basal metabolic rate (BMR). Indeed,
measurement of the BMR was one of the earliest tests used to assess a
patient’s thyroid status. Patients whose thyroid glands were not working
were found to have low BMRs, and those with overactive thyroid glands
had high BMRs. Later studies linked these observations with
measurements of thyroid hormone levels and showed that low thyroid
hormone levels were associated with low BMRs and high thyroid
hormone levels were associated with BMRs. Most physicians no longer
use BMR due to the complexity in doing the test and because the BMR
is subject to many other influences other than the thyroid state.
What is the relationship between BMR and weight?
Differences in BMRs are associated with changes in energy balance.
Energy balance reflects the difference between the amount of calories
one eats and the amount of calories the body uses. If a high BMR is
induced by the administration of drugs, such as amphetamines, animals
often have a negative energy balance which leads to weight loss. Based
on such studies many people have concluded that changes in thyroid
hormone levels, which lead to changes in BMR, should also cause
changes in energy balance and similar changes in body weight.
However, BMRs are not the whole story relating weight and thyroid. For
example, when metabolic rates are reduced in animals by various
means (for example by decreasing the body temperature), these
animals often do not show the expected excess weight gain. Thus, the
relationship between metabolic rates, energy balance, and weight
changes is very complex. There are many other hormones (besides
thyroid hormone), proteins, and other chemicals that are very important
for controlling energy expenditure, food intake, and body weight.
Because all these substances interact on both the brain centers that
regulate energy expenditure and tissues throughout the body that
control energy expenditure and energy intake, we cannot predict the
effect of altering only one of these factors (such as thyroid hormone)
on body weight as a whole. As a consequence, at this time, we are unable
to predict the effect of changing thyroid state on any individual’s body
weight.
