What's the magical formula to
achieve your weight goals?
In order for your weight to stay the
same, the energy (or calories) you consume must equal the energy (or
calories) you expend. In most cases, it’s really a simple matter of
energy balance: “Calories In” must equal “Calories Out.” “Calories
In” includes what you eat and drink. “Calories Out” includes your
resting metabolic rate, thermic effect of food, and physical
activity. Your personal calorie requirement depends on these three
Read on to learn…
What you can do to rev up your
Whether fat burner supplements are
worth your money.
How many calories you can burn
during different physical activities.
Exactly how many calories you need
to meet your weight and fitness goals.
Resting Metabolic Rate
Resting metabolic rate (RMR) is the number of calories it costs for
you to maintain all your internal physiological functions at
complete rest. In other words, it’s the amount of energy required to
keep your heart beating, your lungs breathing, your brain and liver
functioning, and all your cells alive and well at complete rest. RMR
accounts for approximately 65% of your total daily calorie needs.
Several factors affect RMR. Some of these factors you cannot control
because they are part of your genetic make up. As examples, males
and/or tall individuals often have higher RMRs. Having a fever,
growing (i.e. during puberty or pregnancy), living in a cold
climate, and the premenstrual period in a women’s monthly cycle all
increase RMR and calorie needs. Meanwhile, having low levels of
thyroxin (thyroid hormone) or leptin (a metabolism-regulating
protein) in your body decrease RMR and calorie needs.
So what factors can you control? What can you do to rev up your
Two things: 1) build lean body mass and exercise and 2) avoid
restrictive diets. Read on to learn why.
1. Build lean body mass and exercise.
Of the factors you can control, the main one that affects your RMR
is the amount of lean body mass you have. Lean body mass (which
includes muscle tissue) is very metabolically active and accounts
for 75-80% of your RMR. At rest, one pound of muscle burns about
three times more calories a day than a pound of fat (and during
exercise, the metabolic rate of muscle increases substantially
more!). So, people who have more muscle on their bodies burn more
calories just sitting in class than people who have more fat on
Of course, your lean body mass is somewhat determined by your
genetic make-up and your age (things you cannot control). Genes
dictate what body type you have and whether you tend to carry more
muscle or fat on your body. Also, as you get older, your body
naturally shifts towards more fat and less muscle, which results in
a 2-5% decline in RMR (about 75-100 fewer calories per day) every
decade past age 30, unless you do something to combat muscle loss.
What can you do to combat muscle loss and keep your metabolism
You can partly control your lean body mass and prevent the
age-related body composition shift by regular resistance training 2
to 3 times per week. In fact, older women and older men can recover
1 to 2 decades of loss, respectively, with just 2 months of
resistance training 3 times per week. That’s a metabolic boost of up
to 10%! Resistance training may include lifting weights, doing push
ups and sit ups, or holding up your own body weight in yoga poses.
When it comes to aging and muscle loss, "if you don't use it, you're
going to lose it." So, use it!
In addition to building muscle (which is more metabolically active
tissue), very intense exercise sessions can speed up your RMR for
several hours after you stop working out. So, people who have more
muscle AND are training very hard most days of the week need a lot
more calories just to maintain their internal physiological
functions at rest.
2. Avoid restrictive diets.
Restrictive dieting, on the other hand, slows down RMR. Your body
slows down in order to adapt to the lower calorie intake (so it can
function with less fuel). Your body is very smart, and it wants to
protect you. So, it actually begins holding on to every calorie you
eat and storing it as fat (since it’s not sure you will feed it
later). This is one possible reason why people who diet usually gain
back their weight (and then some!) once they return to their normal
eating patterns. Click here for more info on “Do
What about fat burner supplements?
Many dietary supplements are marketed as “thermogenic agents,”
claiming to speed up metabolism and burn fat. These substances
usually contain ephedra, synephrine, caffeine, and/or green tea
extract, and they do have some stimulating effects. They can
increase heart rate, increase blood pressure, and increase
metabolism slightly. But, looking at the big picture, their effect
is relatively minor. And some products can cause serious health
problems. There is no magical pill that can shed pounds without some
life-long adjustments in eating and activity patterns. If something
sounds too good to be true, it probably is. Click here for more info
about fat burner supplements.
Thermic Effect of Food
The thermic effect of food is the amount of calories it costs to
digest, absorb, transport, and store nutrients in your body. Every
time you eat, your RMR goes up slightly and stays up for about 5
hours to fuel these metabolic activities. This may be why you’re
more likely to maintain a healthy weight and keep your metabolism
revved up if you eat smaller, more frequent meals throughout the day
(instead of skipping breakfast and lunch and then stuffing yourself
late at night).
In reality, the thermic effect of food plays only a minor role in
your total calorie expenditure (maybe 5-10% of your total needs), so
it probably has minimal effect on your weight. But, eating smaller,
more frequent meals certainly won’t hurt. If anything, your brain
and muscles will appreciate the steady supply of nutrients
throughout the day, and you are likely to feel better and perform
better in school and physical activities.
Interestingly, researchers have found that the thermic effect of
food varies between obese and lean people. When lean people eat a
meal, energy use speeds up for a while and then drops back to normal
(as expected). Many obese people, on the other hand, do not
experience any change in energy use after eating (i.e. food has no
thermic effect for them). So, while thermic effect of food
contributes little to our overall daily energy needs, this small
amount of energy probably adds up over a lifetime and may explain
why some people stay lean while others gain weight, despite similar
Physical activity includes the calories you spend during normal
daily activities (such as walking to school, brushing your teeth,
fidgeting in class), as well as the calories you spend during
purposeful exercise sessions (like jogging, swimming, and
kick-boxing). As you may suspect, there is huge variability in the
number of calories different people spend in physical activity. Do
you take the stairs or the elevator? Do you walk to school or drive?
Are you fast-moving and fidgety all day, or do you move slowly and
prefer to stay still and relaxed? Do you enjoy sports, weight
lifting, hiking, and aerobics in your free time or do you prefer
reading, painting, or writing? The calories burned in physical
activity vary widely, but it usually accounts for about 25-35% of
your total daily calorie needs.
The exact number of calories you personally burn during different
activities depends on your size (it costs more calories for a larger
person to do the same task as a smaller person), your fitness level
(it takes more calories for a beginner to do the same exercise as an
experienced athlete), and the intensity of the activity (it takes
more calories to run for 30 minutes than to walk for 30 minutes).
Click here to see
how many calories your burn during 30 minutes of different
activities (based on your body weight).
Calculate Your Total Calorie Needs
There are many equations to estimate your total calorie needs based
on your RMR and level of physical activity (NOTE: the thermic effect
of food is usually not accounted for since its role is so minor). It
is important to realize that all these equations are just estimates.
You may need more or less depending on genetic differences in RMR
and your body composition. Consult a qualified health professional
for more information about your personal calorie needs.
Step 1: Estimate RMR
Men Healthy body weight x 11 calories
Women Healthy body weight x 10 calories
IMPORTANT NOTE: This is just an estimate of what your body requires
at rest. If you have more muscle than the average person, you
probably require more calories at rest than this equation suggests.
If you have more fat than the average person, you probably require
fewer calories at rest than this equation suggests. Remember, muscle
tissue is more metabolically active than fat tissue. If you are 30
lbs. or more overweight (and that excess weight is mostly fat, not
muscle), you can use your desired body weight instead of your actual
body weight when calculating your RMR.
Step 2: Multiply RMR by Activity Factor Activity Factors
|Very Light/Sedentary (sitting or
standing all day) e.g. lab/computer work, typing, painting.
||1.20 - 1.30
|Light (walking and some movement
e.g. student, teacher, homemaker, child care worker
|1.30 - 1.45
|Moderate (work at a job with some physical work or
moderate intensity exercise 4-5 x/wk. for about one hour)
e.g. gardening, carrying loads, most recreational exercisers
1.45 - 1.65
|Heavy (work at a job with heavy manual labor or
vigorous intensity exercise 5-6 x/wk. for one or more hours)
e.g. roofer, carpenter, many athletes
1.65 - 1.90
|Exceptional (intense physical training for many hours every day)
e.g. professional or collegiate athletes during their
1.90 - 2.20
What if you want to lose weight?
The only way to lose weight is to create a calorie deficit. One
pound of fat equals 3500 calories. So in theory, to lose ½ pound to
1 pound a week, you have to create a deficit of 250 to 500 calories
per day (either by eating fewer calories or burning more in physical
activity). Of course, genetic differences determine how easy it is
for you personally to lose weight. In one study, researchers overfed
a group of people 1000 extra calories every day for 8 weeks and
found that there was a huge difference in the amount of weight
gained (ranging from 3 to 16 pounds)! The researchers concluded that
the people who gained less weight “wasted” the extra calories by
fidgeting more and giving off more body heat. The people who gained
more weight, on the other hand, had bodies that were more efficient
in storing the extra calories. For more tips on healthy weight loss,
go to “Eating Strategies for Permanent Fat Loss.” To maximize fat
loss, minimize the drop in your metabolism, energy, mood, and
grades, and increase the chances that you won't gain it back, lose
weight slowly! Decrease your intake slightly by 250-500 calories per
day and increase your exercise level. Aim for about 0.5-2 lb. weight
loss per week. If you are very overweight, 2 lb. per week is
acceptable. But, if you only have a few pounds to drop, the rate
should not exceed 0.5-1 lb. per week.
What if you want to gain weight?
The only way to gain weight is to create a calorie excess. So, in
theory, to gain ½ pound to a pound a week, you have to create an
excess of 250 to 500 calories per day. Whether or not those extra
calories go towards building muscle or body fat depends on whether
or not you exercise. Of course, as with weight loss, genetic
differences make it easier for some people to gain weight and harder
for others. If your metabolism speeds way up every time you eat
more, you may have to consume many more calories before you’ll
achieve results. For more tips on weight gain, go to “Eating
Strategies to Gain Weight” and “Frequently Asked Questions about
Bulking Up.” Also, click here for more tips on
what to eat before,
during, and after workouts for maximal results.
Sheri Barke, MPH, RD
COC, Student Health & Wellness Center