Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
Theoretical part
Assessment of energy expenditure using
indirect calorimetry and Harris-Benedict
formula
All events connected with life are bound to energy. In one day, the amount of ATP in
kilograms used up by our bodies approximately equals our body weight. Measurement of
energy expenditure is an important tool in clinical practice, enabling us to determine the
optimal nutritional support of a patient. The energy expenditure of an organism and
consequently the need for energy intake are increased during disease, post-surgical recovery,
and in a state of malnutrition. On the other hand, we need to decrease the energy intake in
patients suffering from obesity. It is particularly urgent in patients who already have
hypertension or diabetes to prevent them from suffering other, more serious consequences like
heart attack, renal failure, or loss of vision. Moreover, diabetes is one of the leading causes of
vision loss in developed countries. Therefore, we cannot underestimate the value of proper
therapy of obesity. Also, the area of nutritional care for athletes is very important. Athletes
need to be placed on an adequate diet that suits their personal needs and the type of activity
that they perform. Finally, it is crucial for each one of us to know our energy expenditure so
that we keep our energy balance (food intake and expenditure) in equilibrium and thus
promote good health. In order to understand how to measure the energy balance of an
organism in one day or during the day, we need to get familiar with some terms like basal,
resting and actual energy expenditure.
Basal energy expenditure (BEE) is the amount of
energy that our bodies spend on basic processes that are
crucial for life, such as the beating of the heart, basic
metabolism of nutrients and regulation of them,
breathing, maintaining body temperature, resting tone of
muscles and the functioning of the central nervous
system that oversees the regulation of homeostasis.
Naturally, there are many more processes involved in the
basal metabolic energy expenditure. When we look at the
microenvironment of every cell, the greatest amount of
energy is spent on the mere maintenance of the resting
membrane potential of a cell. Basal metabolism
represents about 50–70% of the whole energy spent by
the body and forms the basis of the energy demand that
we need to cover with our diet every day. The basal
metabolic rate is defined as the energy used up in a unit
of time in a person in a lying position, at physical and
mental rest, in a thermoneutral environment (22–26 °C),
at least 10–12 hours fasting, and without the effect of
stimulating drugs (e.g. tea, coffee, etc.). It is therefore
not very suitable for measuring hospitalized patients.
However, we can approximately estimate BEE by
Participation of different organs on
basal metabolic rate
Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
Krogh’s respirometer - reservoir filled with oxygen
measuring resting energy expenditure either using indirect calorimetry or assessing it by
calculation, for example using the Harrison and Benedict formula.
Resting energy expenditure is therefore an approximate value of BEE measured in
clinical conditions in a hospital whereby all the following restrictions must be maintained:
 e measure in the morning in a lying position in the bed from which the person hasn’t
stood up yet (to prevent energy from being burnt due to muscle work)
 The examined person must be relaxed and comfortable, but awake
 In a thermoneutral environment (so that we prevent energy expenditure being spent on
thermoregulation)
 Before a morning meal (to prevent energy being spent on digestion and peristaltic
movements) and making sure that there were no proteins in the last meal (proteins have
the highest specific dynamic effect, which is the energy that is spent on digestion,
absorption and metabolism of a nutrient after absorption).
 In addition, we can measure the actual energy expenditure (AEE), which accounts
for the energy that is spent to cover the actual energy requirements, i.e. in
standing position, it is the energy necessary for maintaining the upright position by
antigravity muscles. After physical exertion, the actual energy expenditure basically
covers the increased energy requirements of the heart and lungs that are still at work
trying to bring the deviated homeostasis of the organism caused by the exertion to
equilibrium. Moreover, the body tries to get rid of excessive heat by sweating, and this
requires energy as well. The value of AEE can likewise be calculated by an equation
which you can find in the protocol for this practical. Another option for calculating the
energy output is to sum up all the components of energy expenditure during one day,
and this can be found in the practical on compiling a daily diet.
Indirect calorimetry is based
on the presumption that oxygen
spent by an organism stands in
some relationship to the energy
spent for metabolic processes of
cells. The cells respire and thus
use up oxygen while creating
energy in the form of ATP. This
energy is then expended on
various functions.
To calculate the energy
expenditure of a person, we need
to know the energy equivalent
of the oxygen (EE). For
simplification, we will use the
EE for mixed nutrition (every
nutrient has its own EE, but we
assume that the examined person
eats mixed nutrition during the day). Its value is 20.19 kJ/liter of O2. This means that when
the organism consumes 1 liter of oxygen, it gains 20.19 kJ of energy which is then continually
used (since ATP is an unstable compound, and cannot be stored) for different processes in the
body. Consequently, if we measure the amount of O2 that was consumed, we can calculate the
energy expended by the body. For the measurement of the consumption of O2, we will use
Krogh’s respirometer. This is a device with closed circulation of air, i.e. the subject
Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
breathes both air from and into it. The reservoir is filled with oxygen, and surrounded with
water. The level of the oxygen continually diminishes as the examined person is breathing.
Consequently, the reservoir sinks further and further into the water, and the curve of changes
of volumes in inspiration and expiration sinks as well while the person is consuming the
oxygen, and its slope tells us about the amount of oxygen consumed.
CO2 from the expired air is removed by an CO2 absorber (so-called soda lime consisting of
sodium and calcium hydroxide). Otherwise, CO2 would accumulate in the air (since it is a
closed system) and cause hypercapnia (increased CO2 in the bloodstream). Hypercapnia
would then, through the stimulation of the respiration center in our brain stem, cause
hyperventilation (breathing faster and deeper) and thus spoil our results.
The energy expenditure can be measured also via direct calorimetry, which is based on the
fact that all metabolic processes in the body are connected with the production of heat. Thus,
if we measure the heat produced over some time, we will be able to calculate how much
energy was actually burnt in the body. This method is, however, very complicated and is no
longer used in clinical practice today.
Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
Theoretical part
Compiling a daily diet: principles of proper
nutrition
It is important for everybody to know the basic principles of a healthy lifestyle and nutrition
since it contributes to the prevention of various diseases. There are many diets and
recommendations for a healthy lifestyle available today. Moreover, this field is becoming
more and more commercialized, and money has become more important than the health of an
individual. It is therefore very important to be familiar with this field. Optimal nutrition is an
important part of a healthy lifestyle, which in turn determines almost 60% of our health. The
problem of proper nutrition is particularly important for certain groups in the population that
vary in some aspects pertaining to the way their bodies function. In children, proper nutrition
(both how many calories they eat and what composition their meals have) is essential for their
growth and proper development and functioning of the organs as well as their bodies as a
whole. Pregnant women, whose tastes and needs markedly change during pregnancy, must
also pay special attention to nutrition. Athletes, likewise, depend on an adequate and
individual type of diet, as their bodies are often strained in an extreme way.
Nutrition and disease
In the therapy of certain diseases there are some nutritional restrictions and dietary
adjustments that need to be respected. These restrictions and changes are based on a
knowledge of the pathogenesis of a disease (i.e. the mechanisms resulting in the development
of a disease). As an example could serve a low-protein diet and restriction of fluid intake in
patients with liver failure (for example, in cirrhosis caused by excessive alcohol intake or
chronic hepatitis). The explanation for this is that bacteria of the gut digest proteins and
produce ammonia (NH3), but the ammonia cannot be sufficiently processed by the liver and it
can cause toxic damage to the central nervous system. At the same time, low production of
proteins by the liver and increased pressure in portal venous circulation due to scarring of the
liver (the portal vein brings blood from the gastrointestinal tract and spleen to the liver) can
cause significant swelling, particularly in the abdominal region. This explains the restriction
of the water intake. A nice example of a nutritional recommendation based on a disease and
its therapy could also be the fact that diabetics who are dependent on insulin therapy should
have a snack before they go to bed. This is due to the fact that they are at risk of low sugar
levels (so-called hypoglycemia) during the night because of the effect of insulin. On the other
hand, for patients with type-2 diabetes (those who are not at first dependent on insulin
injections) it is recommended to lose weight and increase physical activity since the resistance
of tissues to insulin, which is the cause of this type of diabetes, can be frequently tackled by
losing weight. All recommendations naturally need to be approved by the physician that treats
the patient.
Food allergy
However, we must mention one disease that might be connected with food and is nowadays very
common. The occurrence of it also shows an increasing trend and we all know it: allergies. An allergic
reaction is an “overreaction” of the immune system to some substances that are called allergens.
Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
Foodstuffs are a significant
source of allergens. Food
allergies can be manifested by
all sorts of symptoms such as
intestinal problems (diarrhoea,
bloating, pain), but also
frequently skin (different types
of rash) or even respiratory
problems. If the causes are
unclear, it is recommended to
start writing down as precisely
as possible the content of one’s
daily diet (for 1–2 weeks). The
correlation between the
occurrence of symptoms and the
type of food can lead to finding
out what the specific allergen is.
We can then attempt to remove
it from our diet, and see if the
problems improve or even
disappear.
Nutritional advice
If we look at the recommendations below, we might say that we have not learnt anything new.
However, once we reconstruct our daily diet from yesterday and compare the reality with the
recommended doses of nutrients, we might be very easily surprised by the “nutritional
mistakes” that we make, much more than we would have admitted before this practical. To be
able to do this, we need to examine in detail all of the components of our diet, including
vitamins and minerals.
It is important to observe not only intake of proper amounts of the food components, but it is
also important that the component come in a suitable and soluble form. For example, we
should eat more polysaccharides (e.g. bread, fruits, vegetables, etc.) than monosaccharides
(e.g. sugar or sweets), and regarding fats, the diet should contain unsaturated fatty acids like
omega 3 or 6 (so-called n-3 or n-6 PUFA) in an optimal amount. They are essential to us since
our body cannot synthesize them. Also, fibre is an essential part of our daily diet. It consists
of polysaccharides (like cellulose) and cannot be digested by our bodies’ enzymes. Since it
draws water, it makes the faeces softer and bigger, and thus promotes peristaltic movements
of the gut. In this way it prevents constipation. It also helps to prevent diverticles (small
pouches on the wall of the colon) and hemorroids (dilated veins in the lower rectum or anus)
that are caused by the increased pressure in the colon due to the difficulty of moving the
faeces forward if they are hard. Moreover, hard faeces can damage the mucosa of the anus
during defecation, causing small but painful fissures.
Nutrition for a healthy lifestyle
 varied and balanced diet
 adequate intake of food rich in fibre, vitamins and minerals like fresh vegetables, fruits
(optimally 5 times per day) and pulses
 drink mineral water (without sugar) and diluted fruit juice
Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
 prefer dark bread and whole-grain pastries (which contain more of some important
minerals and vitamins and particularly fibre)
 restrict consumption of:
 fatty meals and sweets like chocolate, cakes and fatty meat (prevention of caries and
being overweight)
 fried foods, canned foods and smoked foods (these contain carcinogens)
 meat (mainly red – pork, beef) – recommended consumption of meat 150–200 g/week
 exchange red meat for poultry instead (red meat is associated with an increased risk for
certain types of cancer)
 increase consumption of fish (at least twice a week), as these contain unsaturated fatty
acids like omega-3 and vitamin D
 restrict salt intake and avoid salty food like salted peanuts or chips (for prevention of
hypertension)
 alcohol intake only occasionally and moderately (prevention of various diseases like
cancer, or injuries and car accidents)
 increase number of daily meals (the more calories it is necessary to eat the more meals
per day)
 keep an adequate body weight and do regular exercise (at least an hour daily) (gain and
expenditure of energy should be in balance)
You can find the recommended doses for adults for one day in your protocol.
Food pyramid
(http://mariasols.com/wp-content/uploads/2008/05/food_pyramid.JPG)
Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
Theoretical part
Evaluation of nutritional state
Even today, in our developed society, we encounter disorders connected with eating and a
person’s nutritional state. We can find the two extremes, both undernourishment (called
inanition and, in its extreme variant, cachexia) and being overweight (and its extreme variant
obesity). The occurrence of these disorders shows an increasing trend. Both of the extremes
can take their toll, with consequences both somatic (endocrine, e.g. decreased fertility,
cardiovascular, immune disorders, problems with motor apparatus, etc.) and mental
(inferiority complex, depression). If these problems are neglected, they may lead to severe
complications and early death.
For the evaluation of a subject’s nutritional state, the most common parameter is body weight.
However, body weight can be interpreted in many ways, because it informs us neither about
height or fat distribution (amount of subcutaneous fat, e.g. fat in breasts, buttocks or thighs, as
opposed to visceral or abdominal fat which increases the risk of cardiovascular diseases) nor
about muscle mass. Therefore, we use other parameters to sort out these deficiencies, e.g. the
body weight/body height ratio, hip and waist circumference and other indices derived from
them.
Using multiple values to describe the nutritional state helps us to distinguish some
physiological deviations (caused, for example, by the influence of hormones) from already
pathological conditions. Moreover, they can distinguish between men and women pertaining
to their different body constitution. There are many other
parameters determining the nutritional state of an individual that
are used in clinical practice, primarily calculation of active
muscle mass and skinfold thickness. These values can be
determined very precisely in many different ways (dilution
methods, spectrometry or computed tomography – CT).
However, they are complex in terms of equipment and can be
substituted by more simple ones that are accurate enough for
clinical practice, such as measuring the skinfold thickness by a
caliper, measuring active muscle mass by a simple measuring
tape and few calculations, or measuring the fat percentage in the
body by the bioimpedance method.
Measurement of skinfold
thickness by a caliper
Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
Principle of the bioimpedance method
All devices in this practical class use a method called
BIA, i.e. bioelectrical analysis of impedance. During the
measurement, these devices produce an extremely low
alternating electrical current (5V, 25kHz) which passes
through the body. Tissues rich in water (e.g. skeletal
muscles) have better conductivity, while fat tissue is
highly resistant to electrical current and has almost no
electrical conductivity. Consequently, the more fat the
examined person has, the more resistance needs be
overcome by the current. This enables us to determine the
ratio of the amount of fatty tissue to other tissues.
However, it is important to realize that the results of this
measurement are affected by the amount of water in nonfatty
tissues, i.e. by the person’s hydration status. The
more water the examined person has, the lower the fat
percentage will be than in reality and vice versa. That is
the reason why measured values may fluctuate over time
and also when the measurement is performed under nonstandard
conditions, such as immediately after a meal,
after a bath or after consumption of alcohol. Values are
different also in patients suffering from diseases
accompanied by water loss (diarrhea, vomiting, profuse
sweating during exercise or fever), or even in women
during menses. For this practical we will use two types of
devices: a hand to hand device which measures impedance
predominantly of the upper part of the body and bioimpedance scales (so-called foot to foot
measurement) which measure body fat percentage in the lower part of the body. The results
can thus vary due to the different distribution of body fat.
From the clinical terms, it is necessary to mention metabolic (Reaven´s) syndrome here. The
definition of the word syndrome is multiple symptoms (subjective problems), signs (objective
findings), or biochemical markers that occur together, and are characteristic of a certain
disease. Metabolic syndrome comprises:
 Hyperglycemia after fasting (increased level of blood glucose), which may or may not
be a sign of diabetes
 Arterial hypertension (increased blood pressure)
 Dyslipidemia (increased levels of serum cholesterol and/or triglycerides – TGs) and
 Abdominal obesity (determined by measurement of waist circumference)
Bioimpedance scales
Hand to hand bioimpedance
measuring device
Name: Numer: Study group:
This text was supported by project FRMU no. MUNI/FR/1552/2015 (Faculty of Medicine, Masaryk University).
The combination of
these four findings
increases the risk of
occurrence and
development of
atherosclerosis (fatty
and sclerotic plaques)
in blood vessels and
its complications,
such as a heart attack
or stroke. The crucial
step in therapy of
metabolic syndrome is
the therapy of obesity
since obesity plays an
important role in the
development of the
resistance of tissues to
insulin (and thus
hyperglycemia), and
also arterial hypertension (mostly through the activation of the sympathetic nervous system).
Our aim is, therefore, to reduce weight, and motivate the patient to exercise and move around
more.