Eating to win: activity, diet and weight control
Eating to win: activity, diet and weight control

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

3 Fitness and fat metabolism

Fitness levels contribute to our energy expenditure and weight control. As fitness improves it is possible to do more work at the same heart rate and level of perceived exertion; you are able to burn more energy for the same perceived effort. The term metabolism means the breakdown of foods to release energy. You can metabolise fat, carbohydrate or protein to release energy.

In the following activity, you will learn about the link between fitness level and fat metabolism.

Activity 2 Fitness and fat

Timing: Allow about 30 minutes

Read from ‘Increased caloric expenditure’ up to, but not including, the subsection ‘Reduced blood lipids’ on pages 323–326 from Chapter 13 of the book Fitness and Health by Sharkey and Gaskill (2013) [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] .

As you read, answer the following questions:

  1. What is the link between increased fitness and caloric expenditure?
  2. What is the relationship between lactic acid and the use of fatty acids as a source of energy?
To use this interactive functionality a free OU account is required. Sign in or register.
Interactive feature not available in single page view (see it in standard view).


  1. As your fitness level improves your caloric expenditure increases. This is because you generally increase your frequency, duration and intensity of exercise.
  2. At high intensities of exercise, fat and carbohydrate cannot be broken down quickly enough to provide energy, so carbohydrates are metabolised to provide the energy needed quickly, resulting in increases of lactic acid. The presence of lactic acid also blocks the action of epinephrine (adrenalin), which is needed to allow the fatty acids to be used as energy. When your fitness improves, you are able to perform exercise at a higher intensity with less of an increase in lactic acid. This means that you are more able to utilise fat as an energy source.

Having explored how improved fitness can enable us to metabolise fat, you will now look at the effects of diet and exercise on fats in the blood.

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371