Change of phase angle during a weight loss program for older women
Auteur:
Saartje van der Graaff
Nummer:
Datum:
2011200C
Juni 2011
Opdrachtgever
Peter Weijs
Lectoraat en Kenniskring Gewichtsmanagement
Hogeschool van Amsterdam
Domein Bewegen, Sport en Voeding (BSV)
Instituut
Domein
Opleiding
Hogeschool van Amsterdam
Bewegen, Sport en Voeding (BSV)
Voeding en Diëtetiek
1
Titel:
Change of phase angle during a weight loss program for older women.
Auteur:
Saartje van der Graaff
Tsarenhof 23
2402 DH Alphen aan den Rijn
saartjevandergraaff@gmail.com
Nummer afstudeerproject:
2011200C
Opdrachtgever:
Dr. Ir. P.J.M. Weijs,
Dokter Meurerlaan 8
1067 SM Amsterdam
Tel: 020 - 595 34 00
Email: p.j.m.weijs@hva.nl
Docent begeleider:
Ir. A.M. Verreijen
Praktijk begeleider:
S.E. van der Plas (diëtist)
2
Preface
To complete my bachelor program ‘Nutrition and Dietetics’ at the Hogeschool van Amsterdam
(University of Applied Sciences) I have written this thesis about a change in phase angle in women
with age of 55 or older and overweight, who participated in a weight loss program. It is examined if
this change is related to a possibly change of body composition measured after 7 weeks compared to
the baseline data.
To finish this study the willingness of the participants was essential. They took the study product
every day, participated in resistance exercise program for 13 weeks, maintained a hypo-caloric
weight loss diet and filled out questionnaires.
I would like to thank Amely Verreijen, my coordination investigator, for instructions and feedback,
Suzanne van der Plas, dietitian and mentor, for the possibility to interrupt her in case of emergencies,
and Peter Weijs, lector and instructor, for his tips and sharing his experience and knowledge.
I also would like to thank my studentcollegues Jose Oudejans, Inge Dekker, Merel Bron and Stefanie
de Boer who started up this study so we could start immediately to carry out the interventions.
I would like to thank Dagmar Bloeming, Janna Koopman, Sabine van Waes, Tarana Haarsma, Jorinde
Knoester, Margot van Roon and Nicole Toussaint for the co-operation and confidence during the
implementation of this study.
Finally I would like to thank physician Minse de Bos Kuil, physiotherapists Camille Neeter and Freek
van der Kolk, sports instructors Dave Louiszoon, Denise Hamelijnck and Robert Stols and the manager
of Club West, Saskia Rave.
Amsterdam, juni 2011
Saartje van der Graaff
3
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Summary
Introduction
To estimate someone’s body composition bioelectrical impedance analysis (BIA) or bio impedance
spectrometer (BIS) can be used. The BIS is a multi frequency analyzer which uses an alternating
electrical current that enters the body and detects the values of resistance (R) and reactance (Xc).
Calculations of ECW and ICW can be derived based on the Cole-Cole model.
A value which is also displayed by the BIS, is phase angle. Phase angle is calculated directly from the
relation between the reactance and resistance at 50 kHz and mentions something about the process
of resistance if frequency changes from low to high.
At the moment phase angle is mainly used as prognostic value for survival in patients with AIDS or
lung cancer. Phase angle is significantly influenced by age and sex and PA showed a positive
correlation with BMI (due to a higher amount of cells) but a negative correlation with fat percentage.
Other studies showed a positive correlation for phase angle with BMI but a negative correlation with
fat percentage. It is not known yet whether there is some improvement or impairment of phase
angle by weight loss. The objective of this study was to investigate whether a change in body
composition was related to a change in phase angle in overweight women aged 55 or older.
Methods
To answer the research question baseline data of the Muscle Preservation Study were used. The
following data were used to answer the research question of this thesis: the data of the BodyScout
(BIS) and BodPod (air-displacement plethysmography) of week 0 (baseline) and week 7. Relations
were studied using linear regression analysis.
Results
Height, FM%, FM(kg), FFM%, FFM(kg), PA (BIS) were significantly different between men (N=5) and
women (N=22) at baseline. At baseline there were no significant relations between PA and weight,
FM, FFM or BMI. After 7 weeks there were no significant relations for change in weight, FM and FFM
in relation to PA in women (N=19).
Conclusion and recommendations
A new study has to test the relationship between weight and PA in a higher number of subjects and
possibly a higher percentage of men. In this study the average weight loss was not significant in
women (-1.2kg ±2.4) so it is recommended that participants lose more weight in a new study.
Because of the results I advice dietitians not to use phase angle yet for assessing changes in
someone’s body composition. More research is needed to examine influence of weight loss on phase
angle.
Key words: Phase angle, BIS, obese, elderly, weight loss program, women.
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Table of Contents
Table of Contents ......................................................................................................................... 7
Glossary ....................................................................................................................................... 8
Introduction ................................................................................................................................. 9
SF-BIA, MF-BIA and BIS ........................................................................................................................ 9
Resistance and Reactance ................................................................................................................... 9
Impedance ......................................................................................................................................... 10
Phase angle........................................................................................................................................ 10
Methods .................................................................................................................................... 13
Participants........................................................................................................................................ 13
Design ................................................................................................................................................ 13
Measurements of body composition ................................................................................................ 14
Statistical analysis.............................................................................................................................. 15
Results ....................................................................................................................................... 17
Body composition in men and women.............................................................................................. 17
Relation with phase angle at baseline (figure 1 – figure 4) ............................................................... 19
Relation with phase angle after 7 weeks (figure 5 – figure 8) .......................................................... 20
Discussion .................................................................................................................................. 23
Results in week 7 in women .............................................................................................................. 23
Strengths and weaknesses ................................................................................................................ 23
Conclusion and recommendations .................................................................................................... 24
References ................................................................................................................................. 25
7
Glossary
BCM
BIA
BIS
ECW
FFM
FM
ICW
MF-BIA
MPS
PA
SF-BIA
TBW
Body Cell Mass
Bioelectrical Impedance Analysis
Bio Impedance Spectrometer
Extra Cellular Water
Fat Free Mass
Fat Mass
Intra Cellular Water
Multi Frequency Bioelectrical Impedance Analysis
Muscle Preservation Study
Phase Angle
Single Frequency Bioelectrical Impedance Analysis
Total Body Water
8
Introduction
The prevalence of overweight and obesity is rising in The Netherlands.1 Professionals, like dietitians,
often use total body weight to monitor someone’s weight loss. Some of them also use bioelectrical
impedance analysis (BIA) or bio impedance spectrometer (BIS) to estimate someone’s body
composition. Usually BIA is a single frequency analyzer and BIS is a multi frequency analyzer. BIA and
BIS are both portable, safe and have a simple procedure.2
Many different values are displayed by BIS including phase angle (PA). Most dietitians and other
users of BIS are not familiar with these values.
SF-BIA, MF-BIA and BIS
Single frequency bioelectrical impedance analysis (SF-BIA) only offers a current at frequency of 50
kHz. At this frequency the impedance is measured and total body water (TBW) is estimated. TBW
can be split in intra cellular water (ICW) and extra cellular water (ECW). SF-BIA cannot distinguish the
distribution of TBW into ECW and ICW. Hereby SF-BIA is not able to explore variations in levels of
hydration. SF-BIA is also not able to measure values like resistance, reactance and phase angle, which
are explained later in this thesis.3
Multi frequency bioelectrical impedance analysis (MF-BIA) uses an alternating electrical current that
enters the body uses different frequencies (0, 1, 5, 50, 100, 200 to 500 kHz) to provide accurate and
precise estimates of TBW and ECW. ICW is assessed by subtracting ECW from TBW.
The current, entering by electrodes at foot and hand, goes only through cell membranes at high
frequencies (> 50 kHz) and passes the cell membranes at low frequencies (< 50 kHz). Then the same
electrodes detect the current and estimate the values of resistance (R) and reactance (Xc) caused by
the current.
For this study the MF-BIA device Quadscan 4000 is used.2,3,4
Bio impedance spectrometer (BIS) is a different multi frequency analyzer. Using BIS also causes an
alternating electrical current entering the body by electrodes. But this current covers a frequency
range of 5 kHz to 1 MHz. Data undergo a nonlinear curve fitting based on the Cole-Cole model
whereby calculations of ECW and ICW can be derived, because at very high frequency the capacitor
(a passive electronic-circuit component which stores electric charge) behaves as a perfect capacitor
and Ro and R∞ can be predicted (figure 1). 2,3,4,5
For this study the BIS device BodyScout Fresenius kabi is used.
Resistance and Reactance
Measurements with MF-BIA and BIS include assessing resistance and reactance.
Before measurement some data (weight, age and length) are entered in the BodyScout (BIS). Length
is an important variable, because in a tall person the current has to move a longer distance which
causes more resistance.
Resistance arises from the cell membrane and is the opposition, or resistance, offered by the body
to the current. At low frequencies (<50 kHz) the cell membrane stops the current and acts as a
resistor. Resistance thus is the ability to stop the current. At higher frequencies (>50 kHz) the current
flows through the cell membranes.
Reactance arises from intracellular and extracellular fluid and is related to the capacitance properties
of the cell membrane. Reactance estimates the ability of material to slow the current down. At high
frequencies (>50 kHz) the cell membranes can hold the current for a moment, which slows it down.
In this case, a cell membrane can be considered as capacitor. At lower frequencies the current does
not even enter the cell membrane, so the current is not hold.6
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Impedance
Impedance is another outcome of MF-BIA and BIS, and can be measured out of resistance and
reactance. It means that the resistance of a conductor (like the human body) is dependent on the
frequency of the alternating electric current. Simply, impedance is the degree to which a medium,
like the human body, slows or stops the applied current. The more the current is stopped or slowed
down, the higher the impedance. Impedance is measured at different frequencies and so a series of
values is derived. These values are represented by complex points and the curve formed by these
points is called impedance locus (figure 1).7
Figure 1: Principles of BIS; Resistance, reactance and impedance locus in the Cole – Cole plot.
R∞ and Ro, resistances at 100 MHz and 1 Hz, respectively; f c, characteristic frequency.7
Impedance, mentioned before, can be converted to body composition. For this purpose someone’s
body volume is necessary. To estimate someone’s volume the following formula is used by BIS:
Volume = p (solution’s specific resistivity) x L (length in cm)2 / Z (impedance)6
Phase angle
A value which is also displayed by the BIS, is phase angle (PA). Phase angle is calculated directly from
the relation between reactance and resistance. It mentions something about the process of
resistance if frequency changes from low to high. At a characteristic frequency the current flows
through the cell membranes and the cell not able to hold the current for a moment. From now on
reactance is decreasing (figure 2). To measure the phase angle next formula is used (at 50 kHz):
arctangent reactance / resistance x 180° / π 8
The greater the reactance, the greater the capacity of the cell membrane to slow the current down.
This results in a higher phase angle and is associated with a better quality of cell membranes.
Impedance also affects PA. A higher impedance results in a higher (and better) phase angle.
It is not known if the BodyScout (BIS) in this study uses the same formula.
Figure 2: Curve of relationship with resistance and reactance with frequency of the current.2
10
In case of good quality of cell membranes phase angle is high. It is desirable that subjects have high
phase angles because this is related to positive prognostic value. At the moment phase angle is
mainly used as prognostic value because some studies have shown a positive association between
phase angle and survival in patients with AIDS or lung cancer.8
Age and sex have a significant influence on phase angle. Phase angle is lower with greater age and
significantly smaller in women than in men.
In practice phase angle is barely used because most dietitians are not familiar with interpretation of
phase angle because not enough research is done on this topic.
Phase angle shows a positive correlation with BMI (due to a higher amount of cells) but a negative
correlation with fat percentage. It is not known yet whether there is some improvement (increase) or
impairment (decrease) of phase angle by weight loss.8
The objective of this study is to investigate whether a change in body composition is related to a
change in phase angle in overweight women aged 55 or older. Evaluating the effect of weight loss on
phase angle will help dietitians to interpret phase angle. They will know what phase angle exactly is
and which circumstances influence the outcome.
I hypothesize no correlation of phase angle by weight loss. A study of Barbosa-Silva8 (2005) has
shown an increase of phase angle with an increase of BMI, due to a higher amount of cells. A higher
amount of cells results in more reactance capacity which causes a higher phase angle. The results of
this study are a comparison within different BMI-groups. However, in the current study changes
within the same person are evaluated and therefore it is expected that they lose weight. In case of
weight gain enlargement of fat cells starts first and finally the amount of fat cells will increase as well.
In case of weight loss, the amount of fat cells does not decrease. The cells will shrink but the amount
will not decrease so the reactance capacity stays equal. Therefore I hypothesize phase angle will not
be influenced by weight loss.8,9
In case of loss of fat mass I predict an improvement of phase angle, linked to the same study of
Barbosa-Silva.8 Compared to the hypothesis for weight loss this appears inconsistent, because
normally a higher BMI results in more fat mass. On the other hand, fat loss mostly results in weight
loss. But fat loss results in improvement of health and phase angle is a predictor of health. Hence I
hypothesize an increase, which means improvement, of phase angle.9
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Methods
To answer the posed research question, data of the Muscle Preservation Study were used. The
Muscle Preservation study is approved by the Medical Ethical Committee of the VU University
Medical Centre Amsterdam. The Muscle Preservation study aims to investigate the superiority of a
protein supplement or control product on muscle mass on elderly (55+) following a weight loss
program including a hypo-caloric diet and a resistance exercise program.
Description of the methods is based on this study, but only the data at baseline and week 7 of the
BodyScout (BIS) and BodPod (air-displacement plethysmography) were used.
Participants
(Abdominal) Obese elderly were recruited by posters in cafeteria, community centers and sport
schools. Flyers were posted in mailboxes in Amsterdam Osdorp and an article was placed in a local
paper. When interested, people could contact the research team by phone.
Inclusion criteria:
 Age between 55 and 85 years
 If women: postmenopausal
 (Abdominal) Obese: BMI >30 or BMI >28 + waist circumference >88 cm (women) or >102 cm
(men)
 Willingness and ability to comply with the protocol, including: taking the study product every
day, participation in resistance exercise program for 13 weeks, maintain a hypo-caloric
weight loss diet and fill out questionnaires.
 Physiotherapist’s professional view that the subject is physically fit and it is safe to
participate in the resistance exercise program
Exclusion criteria:
 Any malignant disease during the last five years except for adequately treated prostate
cancer without evidence of metastases, localized bladder cancer, cervical carcinoma in situ,
breast cancer in situ or non-melanoma skin cancer.
 Previously known: kidney failure, liver failure, anemia.
 Medication: corticosteroids for systemic use, immunosuppressants or insulin.
 Dietary or life style characteristics: Participation in a weight loss diet three months before
starting and during the study, use of protein-containing or amino acid-containing nutritional
supplements three months before starting and during the study, participation in a resistance
exercise program three months before starting and during the study, current alcohol or drug
abuse in opinion of the sponsor-investigator
 Indications related to interaction with the study product:, More than 10 µg (400 IU) of daily
Vitamin D intake from medical sources, more than 500 mg of daily calcium intake from
medical sources, known allergy to milk and milk product, known galactosaemia.
 Sponsor-investigator's uncertainty about the willingness or ability of the subject to comply
with the protocol requirements
 Participation in any other study involving investigational or marketed products concomitantly
or within four weeks prior to entry into the study (8)
Design
This study was a randomized, controlled, double-blind, parallel-group study.
In this study subjects participated in a 13 week weight loss trial. All subjects received dietary
counseling and resistance training for three times a week.
Subjects were randomized into two groups:
 Active: received one serving of protein supplement per day for a period of 13 weeks. On
training days subjects received a second serving of the active study product.
13

Control: received one serving of control study product per day for a period of 13 weeks. On
training days subjects received a second serving of the control study product.
Body composition, nutritional habits, strength and physical functioning were measured in
week 0, week 7 and week 13.
Dietary treatment:
Every participant received a prescribed diet which contained the amount of calories they needed
based on a BMI (weight in kilograms / height in meters2) of 27, minus 600 kilocalories.10
Weight based on a BMI of 27 was measured by the next formula: 27/height in meters2.
Weight, height and age were filled in the revised Harris en Benedict- formula from Roza en Shizgal11
(1984):
 For men:
88,362 + (13,397 * W) + (4,799 * H) - (5,677 * Y)
 For women:
447,593 + (9,247 * W) + (3,098 * H) - (4,33 * Y)
G = Weight in kilograms / H = Height in centimeters / Y = Age in years
The outcome of this formula was multiplied by a Physical Activity Level (PAL)-value of 1.4 for all
participants. After this, an amount of 600 kilocalories was subtracted to calculate the participants
daily amount of kilocalories.
Besides the diet, all subjects were following dietary counseling sessions every two weeks.
Exercise treatment:
All participants were following a resistance exercise program for 13 weeks. They had to exercise
three times a week for an hour. All participants received their own program based on individual
needs and possibilities. This program was developed by physiotherapists. Training was under
supervision of a certified trainer.
Measurements of body composition
The subjects were measured in week 0 (baseline), week 7 and week 13, and measurements included
BodPod, BIS, questionnaires, BIA, and DXA. Subjects were also asked to fill in a 3-day dietary record
prior to every measurement.
Protocol
All subjects had their measurement on the same day of the week at the same time. All of them were
sober for at least 5 hours. They were allowed to drink water until one hour before measurement and
their last toilet was written down. This because hydration, distribution of water and orientation of
tissues are factors which can affect impedance in a human subject.
BodPod - All participants wore tight clothes like bathing clothes and a swim cap. It was requested to
wear to same clothes during the measurements in week 0, week 7 and week 13. Everyone was
measured twice and if the body volume was deviated by >150 ml, a third measurement was
performed.10
BodyScout - The participants were in supine position for at least two minutes on a treatment table
before measurement was started. Left hand and foot were cleaned with alcohol before Resting EKG
Electrodes were placed. Two on hand and two on foot were placed to connect the electrodes. Arms
and legs were spread as far as possible without hanging over the table.
Explanation of devices
BodPod - BodPod is a device for air-displacement plethysmography which measures the volume of a
person indirectly by measuring the volume of displaced air. From body mass and volume someone’s
density is determined. Subjects with high body density have less fat than someone with a low body
density. Fat mass, fat free mass and fat percentage are calculated through body density by the Siri
formula.
Advantages of air-displacement plethysmography compared to dual-energy X-ray absorptiometry
14
(DXA) or hydrostatic underwater weighing are comfortability, practicality and noninvasiveness.
Besides it is also a reliable and valid technique for both normal and various populations, like elderly
or obese individuals.10,12,13
BodyScout – The BodyScout uses different frequencies (5 kHz to 1 MHz) to evaluate fat free mass,
total body water, intra cellular water and extra cellular water. The current goes only through the cells
at high frequencies (> 50 kHz) and passes the cells at low frequencies (< 50 kHz).2,3
The BodyScout also measures resistance and reactance to calculate the phase angle. PA interprets
the quality of the cell membrane. The higher the number of the phase angle, the better the quality of
the cell membranes.2
Other - Other measurements in this study are not described in detail in this thesis, but include
questionnaires, (a.o. quality of life), BIA, DXA, indirect calorimetry and muscle strength and physical
functioning.
Statistical analysis
SPSS Version 18 was used for all the analysis done for this study. The Paired Samples T-Test was used
to find a significant difference in phase angle, body composition and weight after 7 weeks. The
results of week 13 could not be used for this thesis because these results were not known yet before
the end of this thesis.
Linear regression analysis (y = ax + b) was used to describe the relation between weight loss and
phase angle, within the same group after 7 weeks. A linear regression analysis made clear how
change in body weight, FM or FFM affects changes in PA.
To determine significance an alpha of 0.05 was used.
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Results
46 subjects were screened but finally 28 people were included and measured at baseline. Three
subjects could not be included because they booked a holiday during the study period. For four
subjects the physiotherapist’s view was that they were not physically fit and/or it was not safe to
participate in the resistance exercise protocol. The other eleven participants could not comply to the
study protocol.
For this thesis, the measurements of 27 participants at baseline and the measurements only 24
participants of week 7 could be used. One participant was excluded for this thesis because she was
not measured by BodPod related to claustrophobia. Because PA was compared with data of weight,
FM, FFM and BMI derived from BodPod measurements, her outcomes were not useful for this thesis.
Two subjects dropped out, both of them because of they could not comply to the study protocol
anymore. One subject could not be measured for the deadline of this thesis and could not be
included in this thesis anymore.
Only 5 men were involved in this study, so the results for men were not representative and therefore
men were not included for answering the study question of this thesis.
Body composition in men and women
Table 1 shows differences in body composition within men and women, measured at baseline.
Height, FM%, FM(kg), FFM%, FFM(kg), PA (BIS) were significantly different between men and women.
Table 1: Subjects in characteristics (baseline)
Total
Men
Mean ± SD
Mean ± SD
N=
27
5 (18.5%)
Age (years)
62.9 ± 4.0
64.8 ± 4.7
Height (cm)
165.4 ± 8.7
176.6 ± 8.1**
Weight (kg)
93.6 ± 14.0
103.0 ± 7.1
BMI (kg/m2)
34.3 ± 5.2
33.0 ± 1.0
FM (% )(N=27)
48.1 ± 7.6
35.3 ± 3.5**
FM (kg)
45.0 ± 9.8
36.3 ± 1.7**
FFM (%) (N=27)
51.9 ± 7.6
64.5 ± 3.5**
FFM (kg)
48.6 ± 11.0
66.6 ± 8.0**
Phase Angle BIS (N=28)
5.79 ± 0.65
6.83 ±0.53**
* = p <0.05 and ** = p <0.001 (significantly different from women)
Women
Mean ± SD
22 (81.5%)
62.5 ± 3.8
162.9 ± 6.7
91.5 ±14.4
34.5 ± 5.6
51.0 ± 4.8
46.9 ± 9.8
49.0 ± 4.8
44.6 ± 6.5
5.55 ± 0.39
Table 2 shows differences between body composition after 7 weeks. After 7 weeks, average weight
loss in women was 1.2 kg. On average both men and women lost fat mass and gained fat free mass,
both not significant. No significant results between men and women were find.
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Table 2: Average changes (baseline - week 7)
Total
Men
Mean ± SD
Mean ± SD
N=
24
5 (20.8%)
ΔWeight (kg)
-1.4 ± 2.5
-2.3 ± 2.9
2
ΔBMI (kg/m )
-0.4 ± 0.9
-0.6 ± 1.0
ΔFM (%)
-0.8 ± 2.6
-1.5± 3.0
ΔFM (kg)
-1.3 ± 3.0
-3.1± 4.8
ΔFFM (%)
0.9± 2.6
1.5 ± 3.0
ΔFFM (kg)
- 0.1 ± 2.3
- 0.02 ± 2.8
ΔPhase Angle BIS (N=10)
-0.06 ± 0.23
-0.11 ± 0.30
* p=<0.05 (significant difference between week 0 and week 7.)
Women
Mean ± SD
19 (79.2%)
-1.2 ± 2.4
-0.4± 0.9
-0.7 ± 2.6
-1.0± 2.9
0.7 ± 2.6
-0.2 ± 2.2
0.10 ± 0.19
One of the participants had a very low phase angle measured by BIS; 4.36 at baseline and 4.37 after 7
weeks. Normally outcomes of the Quadscan were not used for this thesis, but measurement of
Quadscan also gave low values for phase angle, namely 4.1 at baseline and 3.9 after 7 weeks.
As far as we knew this subject did not have any medical reasons for deviations in hydration or other
deviations in results. For some measurements phase angle of this subject was excluded because it
was out of range.
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Relation with phase angle at baseline (figure 1 – figure 4)
19
Relation with phase angle after 7 weeks (figure 5 – figure 8)
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Weight, FM, FFM and BMI in relation to PA in women.
At baseline there were no significant relations between PA and weight, FM, FFM or BMI (figure 1 - 4)
in women. It appeared that weight gain or increase of BMI resulted in a better PA (figure 1 and 4).
After 7 weeks there were no significant relations measured for change in weight, FM, FFM and BMI in
relation with PA (figure 5 – 8). It appeared that weight loss resulted in an increase of PA (figure 5).
FM and FFM influence PA neither in baseline, nor after 7 weeks (figure 2a, 2b, 3a, 3b, 6a, 6b, 7a, 7b).
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Discussion
This is one of the first studies exploring the effect of a change in phase angle by women with age of
55 or older and overweight after weight loss. Evaluating the effect of weight loss on phase angle will
help dietitians to interpret phase angle. They will know what phase angle exactly is and which
circumstances influence the outcome.
The answer on the study question is that there is no significant change in PA after weight loss in
women. A decrease of BMI due to a weight loss program does not affects PA either. At this moment
there are no other studies about change of phase angle yet.
The hypothesis is that there is no correlation of phase angle by weight loss, because a change of the
amount of fat cells is not expected. Phase angle is compared within the same group, and in case of
fat loss a subjects fat cells will only shrink, not decrease.8,9 The results accord to the hypothesis.
In this study weight loss was not significant after 7 weeks, so a relation between weight loss and PA
cannot be exactly evaluated.
Baseline results in women
A study from Barbosa-Silva et al.8 shows an increase of PA with an increase of BMI. Normally a high
BMI is related to more body weight. The hypothesis of this study is a positive correlation between PA
and weight or BMI at baseline. This because a higher resistance is caused by a higher amount of fat
cells. This thesis shows no significant relation between weight or BMI and PA. So, the results do not
accord to the literature. This can be caused by the fact that the mean BMI was higher in this study
(34.5 kg/m2 for women) than in Barbosa-Silva’s study (26.0 kg/m2 for women).8,14
Baumgartner’s study shows a negative correlation with percentage of FM and PA in each sex.14 My
hypothesis for FM is a negative correlation with percentage of FM because of results in BarbosaSilva’s study, because less fat results in less fat cells. Less cells causes less resistance, which results in
a lower PA.8 In this study no significant relation between FM and PA was found.
Results do not accord to the hypothesis. Probably the results of Baumgartner’s study are more
reliable, referring to the weaknesses in this thesis, mentioned later in this thesis.
Results in week 7 in women
Barbosa-Silva’s study examined improvement of health in case of fat loss and phase angle is a
predictor of health.8 In case of loss of fat mass I predict an improvement of phase angle. A high
phase angle is a predictor of good health and weight loss results in improvement of health.
Though, in this study there is no significant change in PA in case of fat loss. Therefore PA cannot be
used to interpret lose of fat mass yet.
In this study the way of weight loss is special, because in this study the average weight loss in women
was not significant(-1.2kg ±2.4) including -1.0 kg ±2.9 of fat mass.
Strengths and weaknesses
Due to this double-blind study it is not known yet who got the protein supplement and who got the
placebo and how it influences the results.
It is expected that a protein supplement causes an increase of FFM. There is no study that examined
the relation between PA and FFM, but Kyle’s study shows the relation between PA and body cell
mass (BCM). FFM can be divided in BCM and extra cellular mass. Kyle’s study shows that loss of BCM
is associated with poor clinical outcome. Poor clinical outcome is related to a lower PA so possibly
loss of FFM results in a lower PA. 2 Due to this it is possible that subjects who receive the protein
supplement gain more FFM compared to the control group which causes an increase of phase angle.
Another weak point is the special way of weight loss because of the diet, resistance training
and the protein supplement. In common the participants gain fat free mass but lose even more fat
mass so in average they lose weight. Gaining fat free mass is not common for a weight loss program,
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so the results are not representative for other individuals losing weight. In conclusion, in this study
mean weight loss is not significant, therefore it is not possible to define relations.
Only 5 men are involved in this study, so the results for men are not representative and therefore
men are not included to answer the study question of this thesis.
The last weak point is the small intervention group. The intervention group (N = 28) is small because
we do not end the study before the deadline of this thesis. A new study has to test the influence of
weight loss on PA a larger number of participants who will lose more weight.
A strength of this study is the use of the BodPod, which is accurate enough for assessing body
composition as reasonable alternate to traditional hydrodensitometry.
The results of the BIS are reproducible because the BIS estimates the FFM and TBW in subjects
without significant fluid and electrolyte abnormalities. 15
Compared to other studies, this study has a low drop-out rate, five out of 28. Three of those still had
a measurement in week 7 or a few weeks earlier. Those results are also included in this thesis.
Other studies showed phase angle is lower with greater age. In this thesis no difference is made for
age. All participants are 55 years or older, so everyone was aged between 55 and 72. There are no
differences found in body composition or PA within this small range of age.
Conclusion and recommendations
The main result of this thesis is there is no significant change in PA after weight loss in women. A new
study has to test this relationship with a higher number of subjects and possibly a higher percentage
of men. In this study the average weight loss was not significant (-1.4kg ±2.4) so it is recommended
that participants lose more weight in a new study.
I advice dietitians not to use phase angle yet for assessing changes in someone’s body composition,
given that this thesis does not bring out a relation between weight loss and change in phase angle.
More research is needed to examine influence of weight loss on phase angle.
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