Running to Lose Weight

This section is for people who are starting running to lose weight. There is also an annex for anoraks explaining some of these principles at greater length.

Ten principles of weight loss and running

1. To lose fat, you need to eat fewer calories or burn more energy

Your body stores the excess calories that you consume as body fat. So if you want to reduce your body fat, you need either to consume fewer calories, or burn more energy. Any weight-loss programme is only going to succeed if it delivers one or both of these.

2. Don't diet: run instead

Dieting will reduce your muscle and water content as well as your body fat. It is difficult to keep up a diet, because you continually have to fight temptation. Limiting what you eat can also be unhealthy. Exercise, by contrast, will burn calories, increase your lean muscle and body tone, and raise your metabolic rate. If you increase you exercise, you can continue to eat enough to make you feel satisfied, and get a wide range of vitamins and minerals, without putting on weight. It will improve your appearance, reduce stress, and improve your health.

3. Don't begin a diet and start to run at the same time

It is a bad idea to begin a diet and start to run at the same time. When you are a runner your body needs plenty of fuel and a wide range of vitamins and nutrients. If you begin a diet at the same time as you start to run, you may find you do not have enough energy or other nutrients to run, and you will risk illness or injury. You may want to rebalance the composition of your diet (see below) but do not try to restrict your food intake when you start running.

4. To lose more body fat, exercise more

To estimate the amount of calories you need, first multiply your weight in kilograms by 33. This gives you your calorie requirement for a moderately active person who does not exercise. On top of that, to walk, jog or run a mile uses about 100 calories. (It doesn't matter how fast you do it: the energy used is about the same.) From this, you can calculate the amount of calories you should consume each day to reduce your body fat. Never cut your calorie intake to below 80% of your calorie requirement. Running regularly also increases your resting metabolic rate, and increases your percentage of lean muscle, so increasing your energy consumption throughout the day. Over time, for every extra 6 miles a week you run, your equilibrium body weight will settle at about 1kg lighter.

5. Rebalance what you eat

Eat about 55% of your daily calorie intake as carbohydrates, 15% as fat, and 30% as protein. Within this broad framework, eat a varied diet, with plenty of fresh and unprocessed food to ensure that you get the right vitamins and minerals. Carbohydrate and protein are about 4 calories per gramme; fat is about 9 calories per gramme. Carbohydrates, particularly dietary fibre, tend to be bulky and so make you feel full without providing too many calories. Eat proteins with carbohydrates (eg a handful of nuts when you eat a banana) to prevent your body from overreacting to the sugars.

6. Drink plenty of water

Drinking more water will help your running, your health and your complexion. It will also make your stomach feel more full, and so reduce any tendency you might have to snack. Don't try to lose weight by losing water (eg running in a track suit to make you sweat more.) The weight loss from dehydration will be purely temporary, and the dehydration will make it more difficult for you to exercise as hard or as long, so you will end up burning fewer calories. Dehydration can make you very ill, and in extreme cases may be fatal.

7. Focus on your body fat, not your weight

Exercising will increase your lean muscle, which is more dense than fat. So you may find that when you begin an exercise programme, your weight goes up, or does not fall, because the extra muscle more than makes up for the reduced fat. But you will nonetheless have less fat, and a better toned body.

8. Running more slowly will not burn more fat

You may have heard about the "fat burning zone", or seen machines in the gym which suggest lower exertion levels to burn fat. But running further will always burn more calories – so the best way to burn fat is to run as far as you can. (See the annex for a longer explanation of this.)

9. Exercising part of the body does not reduce the fat in that part of the body

You sometimes see people in gyms exercising their legs in the hope of reducing the fat on their thighs. It won't work. When your body supplies energy to muscles, it does not burn nearby fat. Sadly, the fat often comes off just where you don't want it to! Working particular muscles may improve the appearance of that part of your body by increasing muscle bulk and tone, but it won't reduce the fat there.

10. Don't overdo it

You should not try to reduce your body weight by more than 1% of your bodyweight in a week if you want to do it safely and sustainably. If you continue to run regularly, your body fat will fall away over time. Sit back and enjoy the running. You may find that you do not lose as much weight as you expected, because of the replacement of fat by lean tissue, which is heavier than fat. But your body shape and appearance will improve.

For more information about running to lose weight, see our annex for anoraks.