Weight management: Running is a full weight bearing exercise – you have no help moving your body like in cycling or swimming, so with that in mind, it’s easy to understand why being lighter will be easier. Training for the marathon will more than likely result in some weight loss in most individuals but if you’re struggling to lose weight even with your regular training, it’s a good idea to investigate why. Have a look at how many calories you should be taking in each day, adjusted for weight loss, and then estimate how many calories you are consuming each day. Be mindful of hidden calories from beverages such as juice, smoothies, lattes and alcohol. Maintaining, losing or gaining body mass is all about Energy Balance. Energy in = Energy out = weight/body mass staying the same. If Energy in equals more than Energy out, then you’ll gain weight and the opposite has to occur to lose weight.
Everyone is different and will therefore require differing amounts of energy, especially on training v’s rest days but there are formulae that have been developed to estimate the amount of energy we will need to consume in order to train effectively.
You can work out your total energy requirements by knowing your height and weight and then putting those figures along with your age and gender into this CALCULATOR. Now figure out your activity level and whether you want to maintain, lose or gain weight and you will ascertain how much energy you should have each day.