It can be difficult to know how many calories to eat when you are running. The Department of Health recommends women have an average daily intake of 1,940kcal and men 2,550kcal. However, the exact number needed depends on your age, current weight, height and how active you are.
Sports nutritionist Trevor Bedding (http://www.sportsnutritionist.co.uk/) recommends using the following series of equations to calculate how many calories you need on an average day.
Calculate your resting metabolic rate
If you are female:
Age 10-18 years: (Body weight in kg x 12.2) + 746
Age 19-30 years: (Body weight in kg x 14.7) + 496
Age 31-60 years: (Body weight in kg x 8.7) + 829
If you are male
Age 10-18 years: (Body weight in kg x 17.5) + 651
Age 19-30 years: (Body weight in kg x 15.3) + 679
Age 31-60 years: (Body weight in kg x 11.6) + 879
Based on how much physical activity you do a day, calculate your daily energy expenditure.
Multiply your RMR by the following measure
-If you do very little/ no exercise x 1.4
-If you are moderately active x 1.7
-If you are very active x 2.0
Calculate how many calories you burn each week through running - an approximate guide will be 100 calories per mile. Divide this by seven to find a daily average.
Add the figure obtained from step 3 to step 4 to find our maintenance intake. If you eat this number of calories per day based on your current training regime you will stay at the same weight.
Reduce your calorie intake by 15 per cent per daily average if you wish to lose weight. Multiply your maintenance calories by 0.85% to give you a new calorific total.