In order to lose weight, your calorie intake must be less than your total daily calories burned. In order to figure that number out, you'll need to start by calculating your resting metabolic rate.
The following info is from ACEfitness.org, the American Council on Exercise.
What
Is Resting Metabolic Rate?
BMR
and RMR are estimates of how many calories you would burn if you were to do
nothing but rest for 24 hours. They represent the minimum amount of energy
required to keep your body functioning, including your heart beating, lungs
breathing, and body temperature normal.
- BMR stands for Basal Metabolic Rate,
and is synonymous with Basal Energy Expenditure or BEE. BMR measurements
are typically taken in a darkened room upon waking after 8 hours of sleep;
12 hours of fasting to ensure that the digestive system is inactive; and
with the subject resting in a reclining position.
- RMR stands for Resting Metabolic Rate,
and is synonymous with Resting Energy Expenditure or REE. RMR measurements
are typically taken under less restricted conditions than BMR, and do not
require that the subject spend the night sleeping in the test facility
prior to testing.
These
are used to determine your Total Daily Energy Expenditure
TDEE
= RMR + TEF + NEAT + EPOC + Ex
How Do I Calculate RMR?
There are two main ways to determine how many calories you burn
in a given day. A relatively accurate (but more difficult) method is called
indirect calorimetry, which uses expired gases to calculate the amounts and
types of fuel being utilized.
A less accurate, but much easier, method for
determining RMR is to use one of several different formulas. Keep in mind,
however, that some sources claim these formulas can be off by as much as 1,000
calories, with the majority of error or variation occurring in the calculation
of daily energy expenditure. Several websites, including Health-calc, make it possible to more accurately record daily activity,
which can increase the accuracy of the RMR calculation.
RMR Formulas in Action
Following are sample calculations for a 48-year-old woman who is
165 cm (5’5”) and weighs 75 kg (165 lb) using several popular RMR
equations.
* Revised Harris-Benedict BMR Equations (calories/day):
Male: (88.4 + 13.4 x weight) + (4.8 x height) – (5.68 x age)
Female: (447.6 + 9.25 x weight) + (3.10 x height) – (4.33 x age)
weight in kilograms, height in centimeters, age in years
Sample: 447.6 + 9.25 x 75 + 3.10 x 165 = 1,444 calories
Male: (88.4 + 13.4 x weight) + (4.8 x height) – (5.68 x age)
Female: (447.6 + 9.25 x weight) + (3.10 x height) – (4.33 x age)
weight in kilograms, height in centimeters, age in years
Sample: 447.6 + 9.25 x 75 + 3.10 x 165 = 1,444 calories
* A more accurate formula is the Mifflin-St Jeor Equation(calories/day):
Male: 9.99 x weight + 6.25 x height – 4.92 x age + 5
Female: 9.99 x weight + 6.25 x height – 4.92 x age – 161
weight in kilograms, height in centimeters, age in years
Sample: 749.25 + 1031.25 – 236.16 = 1,544.34 calories
Female: 9.99 x weight + 6.25 x height – 4.92 x age – 161
weight in kilograms, height in centimeters, age in years
Sample: 749.25 + 1031.25 – 236.16 = 1,544.34 calories
For highly athletic clients, the Katch-McArdle equation (BMR) and
the Cunningham
equation (RMR) are better because they consider lean
muscle mass.
What is TDEE and why is it important?
Exercise is easily the most adjustable variable in total daily
energy expenditure. Some sedentary people expend just a little bit above their
RMR in a given day, while others can more than double it. The following list
defines various activity levels and applies an “activity factor” that can be
multiplied by BMR or RMR to calculate TDEE.
·
Sedentary — desk
job and little to no exercise (multiply by 1.2)
·
Lightly Active — light
exercise/sports 1–3 days/week (multiply by 1.375)
·
Moderately Active — moderate
exercise/sports 3–5 days/week (multiply by 1.55)
·
Very Active — hard
exercise/sports 6–7 days/week (multiply by 1.725)
·
Extremely Active — hard
daily exercise/sports and physical job or training (multiply by 1.9)
So for our 48 year old woman – if she is lightly active (maybe
she walks 3 days a week) we would multiply her RMR by 1.375 or 1544.35 x 1.375 = 2123 total daily energy
expenditure. So our lady can consume 2123 calories per day to maintain weight.
She should subtract 500 per day if she wants to lose a 1lb per week.
What Variables Affect Metabolic Rate?
You might find a few observations
about them interesting:
·
When
your age goes up, your BMR and RMR go down.
·
When
your height goes down, your BMR and RMR go down.
·
When
your weight goes down, your BMR and RMR go down.
This means that as you get
older, shorter, and lose weight, your BMR and RMR will go down and you will need to eat less or exercise more to maintain your current weight.
Oh my, it's tough getting old. At least as we get older we get wiser. Well,
hopefully.
What
Are the Best Exercises For Raising Metabolic Rate and Losing Weight?
Unfortunately, this question does not have one simple answer
and research has shown conflicting results (Connolly, Romano and Patruno,
1999). Currently, high-intensity interval training (HIIT) appears to be a
leading contender for the title of best RMR enhancer, and the exercises that
build muscle (i.e., resistance training) are believed to have the greatest
effect on the resting metabolic rate. It is worth noting that hypertrophy-focused
workouts, with high resistance to maximize muscle building, don’t burn a high
number of calories and, likewise, the EPOC is small. A proper HIIT approach,
however, which involves raising the heart rate and calorie expenditure to a
high level and results in a significant EPOC, may be one of the most effective
methods of increasing RMR.
What Does Reducing Caloric Intake Do to RMR?
For a personal trying to lose body fat, one of the worst things
he or she can do is cause a major drop in RMR by fasting from eating. Studies
show that RMR can often be maintained on very-low-calorie diets (VLCD) when
sufficient exercise is sustained (van Dale, Saris and ten Hoor, 1990). However,
if an individual goes on a VLCD without exercise, RMR will be reduced dramatically
and muscle tissue will likely be catabolized as a source of protein for ketosis
to occur. Therefore, to achieve weight loss while also maintaining RMR, calorie
intake should be reduced by no more than 500 calories per day, while exercise
expenditure should be account for approximately 250 to 1000 calories per
day.
Skip the mathwork and figure your TDEE out at http://iifym.com/tdee-calculator/
References
www.acefitness.org
Connolly,
J. Romano, T. and Patruno, M. (1999). Effects of dieting and exercise on
resting metabolic rate and implications for weight management.Family Practice, 16, 2, 196–201.
Johnstone,
A.M. et al. (2005). Factors influencing variation in basal metabolic rate
include fat-free mass, fat mass, age and circulating thyroxine, but not sex,
circulating leptin or triiodothyronine. American Journal of Clinical
Nutrition, 82,
5, 941–948.
van
Dale, D., Saris, W.H., ten Hoor, F. (1990). Weight maintenance and resting
metabolic rate 18–40 months after a diet/exercise treatment. International
Journal of Obesity, 14, 4, 347–359.
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