Scientific report – What to do to collect your data. What you

Scientific report – What to do to collect your data.

What you need to do to complete the report:

Measuring energy intake using a 3-day weighed record method.

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

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 3-day experimental period.

PART 1 MEASUREMENT OF ENERGY INTAKE

Method

Weigh all food that you eat and drink each day, for 3 consecutive days, using dietary scales. Find techniques in Nutritional Science and Research/Dietary Assessment which are currently on the Weblearn pages for this module.

You should start your 3-day weighed intake and physical activity diary from starting 22 February 2024. You should submit your data on 06 March 2024.

Food Science

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 Nutritics. 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 3-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 three 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 kcal/day using the equation as you have been previously shown.

For the calculations, you will need to convert this to kcal per minute (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 = 25 minutes x 2.8 PAR = 70

BMR = 1.2 kcal per minute.

Total energy expended in walking = 1.2x 70 = 84 kcal.

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

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 3 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 (3 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 changes in body weight will not be measured as the duration is only 3 days.