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DT5051 and NU5002 data anlysis(2).pdf

DT5051 and NU5002. Energy balance report. Results.

Sixty-five students participated in the study.

Missing data was removed which left 61 participants

Data was cleaned using boxplots to remove outliers

Left 47 participants; 2 were male, 45 were female.

To ensure a homogenous sample 2 males were removed leaving 45 females.

Descriptive statistics

gender

Frequency Percent Valid Percent Cumulative

Percent

Valid 2 45 100.0 100.0 100.0

All participants were female

Descriptive Statistics

N Minimum Maximum Mean Std. Deviation mean intake 45 752 2548 1611.63 384.281

mean BMR 45 1192 1578 1388.23 108.817

mean TEE 45 1195 3414 2132.26 484.488

weight 45 48.0 90.0 64.622 10.0387

height 45 1.50 1.85 1.6524 .06453

BMI 45 18 34 23.95 3.861

Valid N (listwise) 45

Comment on the distribution of data. Observe that there is a difference between mean intake

and mean total energy expenditure.

Paired samples ttest looking at the difference between intake and expenditure

T-Test

Paired Samples Statistics Mean N Std. Deviation Std. Error Mean Pair 1 mean intake 1611.63 45 384.281 57.285

mean TEE 2132.26 45 484.488 72.223

Notice the difference between the two means

Paired Samples Correlations

N Correlation Sig. Pair 1 mean intake & mean TEE 45 .113 .460

Paired Samples Test

Paired Differences

t df

Sig. (2-

tailed) Mean

Std.

Deviation

Std. Error

Mean

95% Confidence

Interval of the

Difference

Lower Upper

Pair

1

mean intake -

mean TEE

-

520.632

583.396 86.967 -695.903 -345.360 -5.987 44 .000

Should be presented as follows:

t (44) =-5.99;p<0.01

this indicates that there is a significant difference between mean intake and mean energy expenditure, showing that the group were not in energy balance. (intake was significantly different to expenditure)

This is the t-test

This is the p value Notice the difference between the two means

Pearson Correlation between mean intake and mean energy expenditure

Correlations

Correlations

mean intake mean TEE mean intake Pearson Correlation 1 .113

Sig. (2-tailed) .460 N 45 45

mean TEE Pearson Correlation .113 1

Sig. (2-tailed) .460 N 45 45

This is the correlation coefficient indicating that there is little association between intake and expenditure

This is the p value showing that there is no association between mean intake and mean energy expenditure

Linear regression graph between mean energy intake and mean total energy expenditure

The data is widely dispersed around the regression line (r2 = 0.01).

Pearson Correlation between mean weight and mean energy expenditure

Correlations weight mean TEE weight Pearson Correlation 1 .247

Sig. (2-tailed) .102 N 45 45

mean TEE Pearson Correlation .247 1

Sig. (2-tailed) .102 N 45 45

This is the correlation coefficient indicating that there is little association between weight and expenditure

This is the p value showing that there is no association between weight and mean energy expenditure

Linear regression graph between weight and mean total energy expenditure

The data is widely dispersed around the regression line (r2 = 0.06).

COURSEWORK ENERGY BALANCE STUDY MARCH (1).docx

COURSEWORK ENERGY BALANCE STUDY

Background

In order to study some of the techniques used and to highlight some of the problems encountered in the study of energy balance and its regulation in man, all students will conduct a 7-day energy balance study on themselves.

Energy Balance Equation

Energy intake (kJ/d) = Energy output (kJ/d) + Gain or loss of body energy stores (kJ/d)

Reference: Dulloo and Schutz (2011) ‘Energy balance and weight regulation’ in Geissler C and Powers H (eds) Human Nutrition 12th Edition, Churchill Livingstone.

The aim of the report is to identify whether a cohort of students, during the period of time studied are in energy balance.

REPORT WRITING

A study of energy balance

This coursework (1500 words) is designed to give you practical experience of measuring energy balance from measurements of energy intake and expenditure. By doing this coursework you gain further experience of undertaking a 7-day weighed record method to collect dietary intake data. You will also gather information on physical activity to gain a better understanding of concepts in energy balance. In addition you will extend your knowledge and ability to analyse group data regarding energy balance and further develop your skills in scientific report writing.

You will be given further guidance regarding this within the timetabled teaching.

Learning outcomes assessed:

1. Explain the concepts of balance and turnover and the theory and practise of their measurements with particular reference to energy and demonstrate an appreciation of the factors implicated in energy balance regulation in humans.

2. Select appropriate analytical techniques for the experimental study of aspects of energy balance.

3. Have developed an ability to apply nutritional theory to practical situations.

Structure of the report.

The limit is 1500 words +/-10%. Please note that cover page, contents page, tables, charts, graphs, references (in text and full reference list) and the appendices are not included within the word count. Try to write concisely and quote the word count at the end of your report.

The report should be written in the format of a scientific report and should be written in the third person and past tense. Word process the document using Arial font size 12 (used in the module handbook) and 1.5 line spacing.

The report will be submitted on-line. Turnitin has a maximum size limit and reports such as these often exceed this size limit. However Turnitin is a more sophisticated marking tool and is more user friendly than the Weblearn dropbox.

You should create two separate documents 1) The first being the scientific report in PDF and this should be submitted on Turitin. 2) The second your appendices which should be submitted in the weblearn dropbox. This should also be in a PDF and should contain material relevant to your report that would disrupt its flow if it were included within the main body. The raw class data, the 7-day weighed intake diaries, the physical activity diaries, all DietPlan data for the individual days of 7 day-weighed intake must be included here. Avoid using your mobile devices for scanning these documents as the quality is very poor and you are then required to collate separate scanned documents.

Both documents – the scientific report and the appendices must be submitted by the 25th April before 3 pm.

Your report should include the following sections:

Cover page & title.

The main purpose of the title should summarise your work in a single phrase or sentence and should explain the nature of your report. Try to be clear specific and brief.

(You can use the title given in this booklet).

Contents List

The contents page sets out sections and subsections of the report and their corresponding page numbers. The aim is to allow the reader to find specific information in the report easily from the table of contents.

Abstract: (~10 % of the overall word allowance)

This is a summary of your report to allow the reader to quickly understand the reasons for your work, the methods used, your findings (so you should present your key data) and your conclusions.

It should include the following sections which should be structured by using sub-headings:

Background: Two or three sentences to set the context of your work and justification for why the study was necessary. Refer to published work. The aim should be clearly stated at the end of the background.

Methods: Summarise what you did clearly and concisely. Mention the methods used to calculate BMR, the use of PAR, how you assessed changes in body stores and how you measured dietary intake. You could also mention briefly the statistics used.

Results: Write two or three sentences on your main findings and present you key results, indicating any significant difference. Your results should relate to the aim of your research.

Conclusion: Give your final conclusion in one sentence. Make sure your conclusion is

supported by your findings.

Introduction: (~ 30% of the overall word allowance)

The introduction ‘sets the scene’ for your report and provides justification for your work. It should supply background information on the subject area and end with the aims of the practical work. This section should include how and why we measure energy expenditure and our interest in energy balance considering the factors which influence both energy expenditure and the control of energy balance.

Methods: The main purpose of a methods section is to describe the techniques and equipment used to carry out the practical work, and to do so in sufficient detail so that a competent worker could repeat it.

For the purposes of this report and due to the restricted word count it is sufficient to write ‘ Refer to module booklet for further details on methodology for the 7-day weighed record, measurement of physical activity and measurement of energy stores.’

Results: (25 % of the overall word. Remember tables, graphs and figures are not included in the overall word count)

This is where you present your data. This should be done in a logical, clear and simple way using a table(s) and graph(s). The results should be presented neatly and in concise tables. Do not include tables copied from SPSS or other computer packages - select the information that you consider is important. Only polished data should be presented here. Only present class data. Your tables and graphs should be stand alone figures and you should include one or two short explanatory sentences explaining your results. Consider the title of your charts and graphs as they should clear.

You should describe your data and include all variables.

You should also include the following as a minimum:

· Descriptive data and include all variables.

· t-test comparing energy intake and energy expenditure

· Pearson’s correlation for the following:

· Weight and energy expenditure

· Energy intake and energy expenditure

Try to interpret the strength of Pearson’s correlation and be able to reference this.

You should produce two scatterplots indicating 1) the correlation between weight and energy expenditure 2) Energy intake and energy expenditure.

The scatter plots should include the regression line with the r2 value.

Each graph must be given a title, the axes must be labelled and the correlation coefficient stated.

Think about whether the sample population were in energy balance and how you might present the energy balance data.

Discussion: (~ 30% of the overall word allowance)

Comment on the results you have found for the class data. Do you think the results are correct? Are they accurate? Explain why and use references to support your opinion. Briefly describe the major sources of error in the study. How could the study be improved? What can you conclude from the analysis of the class data? Are your results in agreement with those from similar published experiments? There are some key references which will help you which are saved on web learn – please refer to these.

Conclusion: (5% of the overall word allowance)

This may only be a single sentence or one short paragraph but should sum up what you have concluded from the study. It should relate to the aim or objectives stated in the introduction.

References

If you use data from a published source this must be referenced in the body of your report. Referencing correctly is extremely important. You must always include a full reference in your reference list. Use the Harvard referencing system. A section on the Metranet explains this system of referencing: http://metranet.londonmet.ac.uk/services/sas/library-services/referencing/referencing2.cfm

Appendices

The appendices contain material relevant to your report that would disrupt its flow if it were included within the main body. The raw class data, the 7-day weighed intake diaries, the physical activity diaries, all DietPlan analyses for the individual days of 7 day-weighed intake must be included here. This is so that the marker can judge your ability to collect and analyse data. Each appendix should be clearly labelled and referred to where appropriate in the main text.

What you need to do to complete the report:

1. Measuring energy intake using a 7-day weighed record method.

2. Measuring energy expenditure using a seven day physical activity diary and calculated basal metabolic rate.

3. Changes in body energy stores will be assessed by measuring body weight.

4. Entering your data to a Google spreadsheet so that analysis of group data can take place.

For the purposes of this study, it will be assumed that body water content remains constant during the 7-day experimental period.

PART 1 MEASUREMENT OF ENERGY INTAKE

Method

Weigh all food that you eat and drink each day, for 7 consecutive days, using dietary scales. Use the same method and paperwork which you used in the module DI5004/HN5053 Techniques in Nutritional Science and Research/Dietary Assessment which are currently on the weblearn pages for this module.

You should start your 7 day weighed intake from 3/3/16 and complete this on the 9/3/16. You complete the seven day physical activity record so that you are measuring physical activity and dietary intake at the same time.

Food Scales

You will need an electronic food scales accurate to 1-2g for part of your course work. If you don’t have scales at home a set can be borrowed from the university for a short period. Scales can be borrowed and returned Monday or Friday 3.00 to 4.00 pm ONLY from Arun Rajan (Technician) located in the Science Centre, room number SC2-24 (Technician). However the number of scales are limited and provision is purely on first come first served basis. If scales are not available you will need to make their own arrangements.

Please note: Students must return scales immediately after completion of their dietary assessment.

In order to borrow the scales, you are required to pay a deposit (£15 cash or £30 cheque made out to "London Metropolitan University"). This will be returned to the student when the scales are returned (undamaged).

Analysis of dietary intake

As soon as you complete the record, analyse the content energy of your diet by using DietPlan. You should include your weighed intake records and dietary analysis in the appendices of your report.

You will also need to calculate the mean energy intake over the 7-day period. For this study, no information is needed about micronutrients, fibre or the proportion of saturated fat etc and marks will not be given for including it.

PART 2 MEASUREMENT OF ENERGY EXPENDITURE

Record of physical activity

You will use activity diary cards. On these cards, you will see that the day is divided into 24 x one-hour blocks with each block sub-divided into 5-minute divisions. You will record your activities for seven consecutive days (the same days on which you are recording your dietary intakes) using one card for each 24-hour period. Start the diary from the time you get up in the morning, eg if you get up at 07:30, start filling in the activities from that point in the diary and not from 00:00 at the top of the page. Each activity should be recorded to the nearest 5 minutes .

Activity codes

On the front page of the diary is a list of code letters and numbers which are to be used to code each activity. The letters refer to the most common activities, for example:

L = lying and sleeping

ST = standing

S = sitting active (eg during a lecture)

W = walking

Before you start, make up some code numbers to signify all other activities that you think you may carry out during the 3 day study period, for example:

1 = sitting passive (eg watching T.V.)

2 = cycling

3 = eating

4 = washing

Make sure you know what activity each code number refers to - record this information in the diary . There may be unexpected activities that will occur during the day which you will not have coded for, for example, running for a bus. Don’t forget to make a note of these. Try to be as accurate as you can with your recording and try not to change your activities from your normal routine as this will not then be a true representation of your 24-hour energy expenditure. If you undertake activities which take less than 5 minutes, for example going up one flight of stairs, round up the figures if it takes more than 2 minutes; you can make an adjustment next time you undertake the activity on the same day.

Obviously the diary must be filled with activities at the end of the 24 hours. Once the diary is completed, add up the total number of minutes attributed to each activity and record this information . Make sure the total number of minutes adds up to 1440.

For each activity recorded, a physical activity ratio (PAR) or Metabolic Equivalent (MET) is required. These values may be obtained from the references below which is available on weblearn:

Human Energy Requirements: Report of a Joint FAO/WHO/UNU Expert Consultation

· Ainsworth BE et al (1992). Compendium of physical activities: classification of energy costs of human physical activities. Med Sci Sports Exerc 25:71-80.

· Bender DA, Bender AE (1997). Nutrition: A reference handbook. Oxford: Oxford University Press. Page 83-87.

· Department of Health (1991). Dietary reference values for food energy and nutrients for the United Kingdom. London: HMSO. Page 205.

Before total energy expenditure can be calculated from the activity diaries, it is necessary to calculate basal metabolic rate (BMR). You should calculate BMR in KJ/day using the equation as you have been previously shown.

For the calculations, you will need to convert this to kJ per minute (1 MJ = 1000 kJ and 1 day = 1440 minutes).

Calculation of energy expenditure (activity diaries and BMR)

The following example shows how the energy expenditure cost of an activity can be calculated by combining (a) the physical activity ratio (PAR) for each of the activities recorded in the activity diary with (b) the BMR calculated from the Henry (2005) equation:

Activity = walking for 25 minutes (out of 1440 minutes).

PAR for walking = 2.8

cost of walking = 70 (25 x 2.8)

BMR = 5 kJ per minute.

Total energy expended in walking = 70 x 5 = 350 kJ.

The total cost of all the activities performed over the 24 h period will equal the 24 h energy expenditure.

Calculation of total energy expenditure

Use the data obtained from the activity diaries

Calculation of energy expenditure (activity diaries and BMR)

The following example shows how the energy expenditure cost of an activity can be calculated by combining (a) the physical activity ratio (PAR) for each of the activities recorded in the activity diary with (b) the BMR calculated from the Henry (2005) equation:

Activity = walking for 25 minutes (out of 1440 minutes).

PAR for walking = 2.8

cost of walking = 70 (25 x 2.8)

BMR = 5 kJ per minute.

Total energy expended in walking = 70 x 5 = 350 kJ.

The total cost of all the activities performed over the 24 h period will equal the 24 h energy expenditure.

Calculation of total energy expenditure

Use the data obtained from the activity diaries, PAR values and BMR to calculate your total energy expenditure for each of the 7 days.

PART 3 MEASUREMENT OF CHANGES IN BODY ENERGY STORES

Background

Energy in the body is stored predominantly as fat (adipose tissue) with smaller quantities of carbohydrate (glycogen). Protein stores (predominantly muscle but also the essential organs) will only be used as a source of energy in the absence of an adequate energy intake or certain disease states. It is difficult to measure body fat and glycogen stores accurately. Changes in body weight are a very crude measure of body composition changes, particularly over such a short period of time (7 days). Body weight fluctuates on a daily basis and this usually reflects changes in hydration status. Small weight changes do not necessarily indicate changes in body energy stores. However, for the purpose of this practical the body weight will be used because of the difficulty of undertaking other more accurate methods. There will be an opportunity to study body composition techniques in year three.

Method

Record your weight (kg) on the day that you start the study and on the day that you start weighing your food and recording your activity finish the study and again on the day that you finish the study. Weigh yourself at the same time on each day wearing the same light clothes and empty your bladder immediately before the weight is recorded.

The energy value of body fat is 39.4 MJ/kg or 39400 kj/kg. (Elia.M., Stratton R., Stubbs J. (2003) ‘Techniques for the study of energy balance in man’ Proceedings of the Nutrition Society, 62, 529-537.)