| Stay energized by improving your fitness level. How diet and exercise can alter your metabolism. |
Resting
Metabolic Rate (RMR) can justifiably claim 60% to 75% of our Total
Energy Expenditure (TEE). Simply put, TEE, is the total amount of
energy that we expend throughout an entire day. Digestion and
absorption of food is called the Thermogenic Effect of Feeding (TEF)
and accounts for 5% to 10% of our TEE.
Energy expended via physical activity is
called the Thermogenic Effect of Activity (TEA), which comprises
roughly 20% to 30% of our TEE. Body Surface Area (BSA) is a major
determinant of RMR, however, voluntary behaviors such as diet and exercise influence RMR in a positive manner.
Calorie restrictive diets can decrease RMR.
I am sure that you have heard the story, someone diets in an extreme
fashion and later regains their weight loss as they return to their normal eating patterns. Your metabolism is what you make it.
Scientific evidence notes that TEE is the
most important value when attempting to manipulate energy balance. Let
us probe further into the involuntary RMR, which has been and is
currently utilized in countless research studies. RMR is measured
resting following a 12-hour fast, which assists in controlling the
impact that the TEF and TEA usually has on RMR.
 |
|
 |
Resting Metabolic Rate Calculator.
Bodybuilding.com has made your life a lot easier with these easy access fitness calculators. Calculate your rmr here.
[ Click here to learn more. ] |
|
 |
|
What is Resting Metabolic Rate (RMR)?
What exactly is RMR? RMR represents all
energy necessary to maintain respiration, blood pressure, and heart
rate. Specifically, it is thought that RMR is distributed as follows:
(7%) kidney function, (10%) heart, (18%) skeletal muscle, (19%) brain
function, (27%) liver function, and (19%) other vital processes.(1)
Figure 1. TEE = total kilocalories expended each day.
An estimated 60% to 75% = RMR, 20% to 30%= TEA,
& 5% to 10%= TEF(1).
| |
Female Athlete |
Avg. Wt Female |
Obese Female |
| Height |
5'7" |
5'7" |
5'7" |
| Weight (Wt) |
135# (61kg) |
140# (64kg) |
185.5# (84kg) |
| Body Mass Index |
21 |
22 |
30 |
| Body Fat % |
20.25# (15%) |
42# (30%) |
65# (35%) |
| Lean Body Mass (LBM) |
114.75# (85%) 52.2kg |
98# (70%) 45.5kg |
120.5# (65%) 54.7kg |
| RMR |
1419K/D |
1441K/D |
1637K/D |
| RMR per kg BW |
23K/kg |
22.5K/kg |
19.5K/kg |
|
Figure 2.
Compare three 30-year-old mesomorph females having identical height.
The obese and average women have a low RMR per kg of body weight when
compared to the athletic woman. Conversely this equates to the athletic
female burns more calories per kg than does the other women.1
|
Interesting determinants of RMR include the phase of the female menstrual cycle and the release of thyroid hormones, which are categorized as catecholamines. The later events can actually increase RMR during times of fertilization.
Compellingly, when one restricts energy
intake too severely a decrease in triiodothyronine (T3) and
norepinephrine will lessen RMR. To a certain extent RMR is based solely
from genetics, however RMR can be permanently altered. RMR will
increase in reaction to extremes in the body's temperature.
Additionally, it is estimated that the
luteal phase or fertile portion of the menstrual cycle can increase RMR
by 5%. Ovulation occurs during the luteal phase when the female
produces progesterone thus increasing body temperature.
The elevated temperature acts as an
incubator for the maturing fertilized egg, granted conception has
occurred. This increase in temperature involuntarily elevates the
female's resting metabolism. Many factors of RMR are beyond our
control, however voluntary behavioral changes such as diet and
exercise, can influence RMR.1
Does Diet And Exercise Effect The Resting Metabolic Rate?
To answer the age old question does dieting
decrease the RMR we look at a meta-analysis. Twenty-two studies
focusing on diet and RMR were compared.
Thompson and coworkers have determined that
RMR does indeed decrease to a significant degree when an individual is
compliant with a diet regimen that is composed of less than 941
calories a day. For the record, the studies primarily targeted females
between the 31 and 45 years old.
What about dieting with exercise? Will it
make a bad situation worse? The same researchers conclude, if a healthy
diet is prescribed by a qualified professional (in the US & Canada
this is a Registered Dietitian) and the subject is well monitored, loss
of FFM should be no more than 20% to 30% of the total weight loss. This
amount is considered reasonable as researchers believe that the results
of healthy weight loss is roughly 25% LBM and 75% adipose tissue (fat).
At first glance it seems as if exercise may allow an individual to maintain more LBM if they exercise while dieting.1
What about different types of exercise
utilized during a period of caloric restriction, will this make a
difference in RMR? In a 3-month study, 69 clinically obese females were
assigned to 1 of 4 groups. There was a diet only "control group", diet
and endurance exercise, diet and resistance training, and diet and endurance exercise plus resistance training group.
The subjects consumed a very low calorie
liquid based diet containing 522 calories a day. Amazingly the changes
in weight, body fat percentage, and LBM were not statistically
different between all groups. However, a decline in RMR was noted and
expected.
Due to the extremely low calorie diet an
approximate decrease of 7% to 12% of RMR was observed in all groups.
The effects of resistance training were measured utilizing a strength
index calculated as the 1 repetition maximum (1 Rep Max).
Values for the bench press, latissimus pull-down, leg extension, and leg curl
were studied. A 6% decrease in strength was noted in the diet only and
in the diet plus endurance exercise group. Astonishingly a 10% strength
increase was noted in the resistance-training group and a 3% increase
was noted in the endurance plus resistance training group.
In these studies neither the endurance
exercise group nor the resistance training exercise prevented the
severe low calorie diet-induced decline in RMR and the individuals
still had a significant increase in strength.1
The Impact Of Nutrition And Exercise On Both Sexes
This research thus far has targeted the
female population, McCargar probed further to find results that were
well rounded. This report focuses on the effects of nutrition and exercise and the impact that they have on body composition in both sexes.
The researchers Ballor and Poehlman
examined 46 human studies in an effort to determine how training and
gender influence body composition. All studies were at the minimum 4
weeks in duration. A diet restriction, and body composition determined
by skin fold calipers or hydrostatic technique was conducted in each study.
It is important to note that not all
studies included an exercise program; therefore comparisons were
differentiated between the diet groups and diet and exercise groups.
Furthermore, differences were noted between the male and female
subjects.
The fundamental findings revealed that the
loss of LBM was significantly less in the diet and exercise group,
additionally; this was consistent for both sexes. Approximately 72% of
the weight loss was body fat and 28% of weight loss was from LBM in the
males.
In female subjects 76% of weight loss was
from body fat and 24% from LBM. The review of these studies revealed
that the conservation of LBM was possible with modest resistance
training done 3 times a week at a low to moderate intensity. That
review crushed the common belief that it is harder for women than it is
for men to lose weight. The females had an average of 4% more fat loss
and a conservation of 4% more LBM than that of the male subjects.1
Does Increased Food Intake Increase RMR?
It takes energy to burn energy and there is
scientific evidence that suggests an increased food intake increases
RMR. This method has been exhibited in patients suffering from anorexia
nervosa. Patients that participated in a professional nutritional
replenishment program increased their RMR. If performed scientifically,
increasing ones food intake can evolve a swell in RMR, a rise so
colossal that it outweighs the possible increase in body mass.
It is widely known and accepted that
exercise increases metabolism. To be precise the elevation in
metabolism occurs during exercise and immediately following. A study,
which revealed a statistically significant increase in RMR, was
conducted. The subjects consisted of 18 individuals their ages averaged
to 66 years old.
The study involved 10 males and 8 females
who were embarking on a cycling regimen for 8 weeks. The subjects were
going to cycle 3 days each week. During the first week subjects cycled
at 60% of their maximum oxygen consumption (VO2 max) till 150 calories
were combusted. In their eighth week, subjects cycled at 80% VO2 max
till 300 calories were combusted.
Their body weight did not change
significantly; therefore it can be said that they did not gain or lose
LBM or fat throughout the 8-week study. VO2 max increase was
statistically significant. At the start of the program VO2 rose from
1.9 Liters of oxygen a minute (L/min) to 2.1 L/min.
When measured, cycling enhanced RMR by 11%.
Pre-study the calories burned were 1.17 calories per minute versus the
post-study results of 1.29 calories a minute. The noted increase in
metabolism is not directly related to exercise alone, an energy flux
had to have taken place.
Because the subjects did not experience
weight change, an additional intake of food had to have been consumed
in order to compensate for the extra energy expended in the study. This
study reinforced what was found in the anorexic study, nutritional factors can change metabolism, in this instance the effect related to endurance exercise.
As depicted earlier,
adequate nutritional intake appears to be vital in maintaining the
energy producing processes of metabolism. For individuals attempting to
lose weight, adequate intake complements exercise and restricted intake
antagonizes exercise regimens.
Placing The Right Emphasis On Diet And Exercise
Maintaining an energy flux is important and
it can be said that increasing LBM via resistance training should
increase RMR. Although I advocate and firmly believe in diet and
exercise in regards to weight loss, gaining LBM, and increasing RMR,
people place unrealistic expectations on their regimens.
A researcher named Zelasko addressed this
and stated that the way individuals perceive the role of exercise in
weight loss and energy expenditure has become rather exaggerated
through time. The major factor in losing fat is time, said Zelasko, and
if TEE would be focused on, high intensity exercises would prevail.
Even though high intensity training uses a
low percent of body fat, it disburses more fat energy as well as TEE.
All this energy and fat utilization does not occur at that given time
but rather in context of the entire day. TEE is critical in determining
energy balance.
Most diet and exercise regimens will allow
RMR to remain relatively fixed, however if a person increases their LBM
they will burn more calories per kilogram of total bodyweight (Figure
2) thus enhancing their RMR. The TEF and TEA comprises the remaining
energy expended factors, furthermore they are the most variable as well
as the most likely to make a change.
Exercise regimens are of utmost importance,
but emphasize on being consistent foremost, then utilize the acronym
F.I.T., which stands for frequency, intensity, and time. Unplanned
exercise and daily physical activity are also key factors when
increasing RMR is the topic at hand.
Additionally, let us not forget my favorite
phenomenon, the TEF; consuming tons of fibrous vegetables daily can
increase your metabolism via the calories burned during digestion.
Therefore it is the total amount of energy you expend in a day that
should be considered if flourishing long-term weight reduction and
maintenance is your ultimate goal.1
Conclusion
In culmination it can be
said with statistical significance that diets restricting intake less
than around 1000 calories a day should be avoided, as they can decrease
RMR and furthermore antagonize the many benefits associated with
exercise.
The suggested caloric intake falls within
the REE and TEE, which represents a caloric restriction of 15%-20% for
healthy and gradual weight reduction.
Exercise should be part of all weight
reduction programs. Anaerobic activity done minimally 3 times a week at
low to moderate intensity gradually increasing over time is suggested
and adding resistance training will be advantageous allowing LBM and
RMR to remain somewhat preserved.
TEE should be the main consideration in all
strategies attempting to alter energy balance in a positive way. The
TEF and TEA comprises up to 40% of TEE and they are the most variable
and likely to make a change utilize them.
High intensity exercises have the greatest
impact on TEE. If one increases these they have then shifted the normal
curve positively in their favor and have made one of the most difficult
things in the world become a reality.
Shedding body fat and gaining or maintaining LBM takes planning, dedication, and can be considered an artful science in it self1.
Reference
- McCargar LJ. Can diet and exercise really change metabolism? Med Gen Med 1999; 1(1).
littlekahuna69@hotmail.com
