Photograph of pages 2 and 3 of 'Big Picture: Fat'

Infographic: Fat by numbers

A snapshot of the role of fat in our lives

This infographic originally appeared on pages 2 and 3 of ‘Big Picture: Fat’. You can download a copy of the standalone infographic at the bottom of this page.

Putting this diagram together, we found that different sources gave different numbers for the same thing. Why don’t they match?

Well, data can be interpreted in different ways, and estimates can be made using different methods and different baseline data. Definitions matter, too – different sources might define ‘healthy’ or ‘fat’ differently.

Which should you choose? The source itself is important – is it from a primary or a secondary source? Is it reliable? Is it recent? Is it from a biased or an impartial organisation? Do your sources agree?

Here, we have given you some background information on which data we used and why. We also have included some discussion questions – you may like to discuss these as a group or think about them as part of an individual activity.

Upper limit of body fat range 

For this graph, we used data from However, even on this single web page, the numbers don’t seem to agree.

For example, in the first paragraph it says “In general, the total body fat percentage (essential plus storage fat) is between 12% and 15% for young men and between 25% and 28% for young women”, yet Table 13.2A gives different, lower figures for the “average population”.

  • Why do you think it’s hard to give a definitive single number for the average body fat percentage for a man or woman? 
  • On this graph, we showed the upper limit of the range of body fat percentages for different people. Would you have used the upper limit or some other number from the web page? Why?
  • Look at Table 13.2B on that web page and identify two or three sports that you associate with having a bigger body frame. Now look at the body fat percentages for these sports. Does anything surprise you?

Energy content of different substances

For this graphic, we wanted a simple way to compare how much energy is released when a given mass of a particular nutrient is respired. We chose to use grey dots, with one dot representing 1 kJ per gram.

We got the information for this from the NZ Nutrition Foundation. This is one of many places that give these figures for the energy released when certain foods are respired. Where do you think these numbers came from originally (ie what is their primary source)?

  • Look at the graphic. How much more energy do you get when a gram of fat is respired compared to that from a gram of carbohydrate? Give your answer both in kilojoules and as a proportion.
  • Look at the amount of energy in a gram of alcohol. Is this more or less than you expected?
  • Alcoholic drinks sold in the UK must include information on the number of alcohol units they contain (one unit is 10 ml or 8 g of pure ethanol). Do you think including information on the amount of energy in alcoholic drinks might influence the amount people drink? 

Food that supplies daily limit of saturated fat for women and men

In this graphic, we focused on saturated fat. In the UK, the Department of Health recommends that a person’s saturated fat intake should not exceed 11% of their total energy intake from food. For the “average man”, this means no more than 30 g of saturated fat per day, and, for the “average woman” no more than 20 g. These limits are for anyone over the age of five years.

To find the amount of fat in items we had to use a variety of sources. For the mackerel, we used the British Heart Foundation as a source. For the coffee, we used Costa as an example. For the pizza, we consulted the Pizza Hut site.

  • For this graphic, we chose to compare oily fish, coffee and pizza. Did anything surprise you about how much or how little of each of these provides the daily limit of saturated fat?
  • Which of these three things would you argue is the “healthiest” foodstuff? Why? Hint: think about the type of fat each of them contains.
  • Write down three things you ate recently. Do an internet search to work out how much saturated fat was in each item. What proportion of your daily recommended maximum (women 20 g, men 30 g) did each contain? Draw your own version of this graphic to show what you found.

Mass of fat

Here, we compare the mass of fat in London’s largest ever sewer fatberg (ugh!) and a blue whale. The information on the fatberg came from this newspaper article.

The whale was a bit more complex. The maximum mass of a female blue whale is 180,000 kg, according to the US charity Whale and Dolphin Conservation. According to this BBC article, the body fat percentage of a blue whale is around 35%. So we calculated the fat mass by working out that 35% of 180,000 kg is 63,000 kg.

  • Name three ways that you could check whether the 15 tonnes figure quoted in the newspaper article about the fatberg is true and accurate.
  • As well as being disgusting, fatbergs are costly. Do an internet search to find out what your local water company says about disposing of fats and waste into the sewer network. Thinking more widely across the UK, can you find anything about how much it costs to remove fatbergs?
  • How do you weigh a whale? Scour the internet and find out how we calculate the mass of these massive marine mammals.

Length of time a blue whale can live off its fat reserves

For this graphic, we got the length of time from the Cool Antarctica site, which says: “Blue whales are thought to feed for 8 months of the year and then fast for the other 4 living off their reserves of fat or blubber built up during the days of plenty.”

  • We converted four months into 120 days for this infographic. Why?
  • Thinking beyond marine mammals, name some other organisms that rely on significant fat stores to keep them alive. What is it about their environment or behaviour that makes them so reliant on stored energy?
  • How much energy is stored in the fat of an average person? Do an internet search to find the ‘average’ mass of a British man or woman, and then find an ‘average’ percentage body fat to calculate the fat mass. Then use the fact that there is 37 kJ stored per gram of fat to calculate the amount of energy contained in their fat.
  • A man needs around 10,500 kJ a day and a woman 8,400 kJ to maintain their weight. It would not be healthy to get all of your energy from fat, of course, but, for the sake of argument, how many days would the energy contained in the fat of the average man or woman last?

Downloadable resources

About this resource

This resource was first published in ‘Fat’ in December 2015.

Statistics and maths, Ecology and environment, Physiology, Health, infection and disease
Fat, Food and Diet, Number Crunching, Populations
Education levels:
16–19, Continuing professional development