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The nutritional requirements for adults do not change between the ages of 19 – 50 except during pregnancy and in breast feeding. Energy requirements are reduced as growing stops but factors such as age, gender and activity levels must be taken into consideration. Below is guidance on the knowledge required before you start to prepare for dieting: Areas covered below before we move on to diet plans are:

1. Body Mass Index
2. Basal Metabolic Rate
3. Physical Activity levels (PAL)
4. Food Labelling
5. Guideline Daily Amount (GDA) and the Recommended Daily Allowance (RDA)
6. The glycaemic index (GI) and the glycaemic load (GL)

1. Body Mass Index (BMI)

Body Mass Index, or BMI is the customary method used to measure obesity. It's a calculation of your weight-to-height ratio and can provide insight into risk for diseases.

Why is it important to know your BMI?

Your Body Mass Index is an important number to use when assessing how much fat you have and how much fat you have to lose. For example; an ideal BMI would be between 20 – 24.9, over 25 and you are approaching overweight and over 30 and you are heading for obesity. These are currently government guides.

To the right is a table for a quick reference or alternatively you can use the calculator provided by

BMI calculator - agreed to the T&Cs
Use the code below to embed the calculator to the website.

content provided by NHS Choices

2. Basal Metabolic Rate or BMR

What is BMR?

BMR is the number of calories your body would burn if you rested in bed for the whole day, it is the total no. of calories that are spent to maintain basic body functions. BMR varies for individuals and decreases with age. It is very important to know what your BMR is for your dieting planning. Again use the formula below for a quick reference.

Men BMR = (10 x weight in kg) + (6,25 x xheight in cm) - (5 x age in years) + 5
Women BMR = (10 x weight in kg) + (6,25 x xheight in cm) - (5 x age in years) - 161

For example; a girl that is 165 cm in height, weighs 54.4kg and is 49 years of age equates to BMR (PAL= moderate exercise 3 times a week) =

Female BMR = (10 x W) + (6.25 x H) – (5 x Age) - 161

W = Weight, H = Height (metric measurements) and your Age in years
BMR = (10 x 54.4) + (6.25 x 165) – (5 x 49) - 161
BMR = 544 + 1,031.25 – 245 -161

Therefore = 1,169.25kcals

3. Physical Activity levels (PAL)

Once you know your BMR then you must also multiply the total with your Physical Activity levels (PAL - see table below) to illustrate your daily calorific requirements. As already stated, consume too many calories you will gain weight, don’t consume enough calories you will begin to lose weight?

PAL Description Example Comments if required
1 Inactive Sleeping BMR x 1
1.2 Little or no exercise Sitting at desk working BMR x 1.2
1.375 Light exercise 1-3 days per week BMR x 1.375
1.55 Moderate exercise 3-5 days per week BMR x 1.55
1.725 Heavy exercise 6-7 days per week BMR x 1.725
1.9 Very heavy exercise Twice per day, extra heavy workouts BMR x 1.9

Exercises moderately 3 times a week = 1,169.25 x 1.55 = 1,812kcals

Therefore BMR including PAL = 1,714.54kcals (1,715kcals rounded up)

4. Food Labelling – Carbs, Fats and Protein

Our energy sources come from carbohydrate, fats and protein. These are called our macro-nutrients. As a further basic guide when developing your meal plan consider your calorific intake with the figures below:

1 gram of fat = 9 kcals (38 kJ)
1 gram of carbohydrates = 4 kcals (17 kJ)
1 gram of Protein = 4 kcals (17kJ)
kJ is the measure used to illustrate energy of which fuel (fat, carbohydrates and/or protein) is converted. The term kJ is sometimes used in conjunction with Kcals to illustrate the calorific value of a food on its label.

For example: Food labelling

5. Guideline Daily Amount (GDA) and the Recommended Daily Allowance (RDA)

After working out your BMR’s now we can work towards government guidance for Guideline Daily Amount (GDA) and the Recommended Daily Allowance (RDA) of different nutrients, see table below. GDA and/or RDA can sometimes be referred to as Reference Indicators (RI). It should be remembered that RDA and GDA are a guide and not a target.

Men Women
Fat 95g 70g
Saturated Fat 30g 20g
Sugars 120g 90g
Protein 55g 45g
Salt 6g (no more than) 6g (no more than)
Fibre 18g (or more) 18g (no more than)

6. The glycaemic index (GI) and the glycaemic load (GL)

Understanding glycaemic index and glycaemic load allows for a greater understanding of the terms used simple and complex carbohydrates and the effects it has on our bodies.

The glycaemic index (GI) is a numerical system of measuring how much of a rise in circulating blood sugar a carbohydrate triggers–the higher the number, the greater the blood sugar response. So a low GI food will cause a small rise, while a high GI food will trigger a dramatic spike. A GI of 70 or more is high, a GI of 56 to 69 inclusive is medium, and a GI of 55 or less is low.

The glycaemic load (GL) is a way to assess the impact of carbohydrate consumption that takes the glycaemic index into account, but gives a fuller picture than does glycaemic index alone. A GI value tells you only how rapidly a particular carbohydrate turns into sugar. It doesn't tell you how much of that carbohydrate is in a serving of a particular food. You need to know both things to understand a food's effect on blood sugar. That is where glycaemic load comes in. The carbohydrate in watermelon, for example, has a high GI. But there isn't a lot of it, so watermelon's glycaemic load is relatively low. A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low.


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