Drink more water. Being dehydrated by 1% can decrease performance by 10%. Experts suggest you drink half your body weight in ounces per day if you are sedentary and 20 oz more per hour of working out. That means id you are 160 lbs you should drink 80 oz of water as a baseline before taking into account what you lose by working out. I don't know how that works out for Kg...sorry metric friends! Some people sweat more than others so I suggest weighing yourself naked before a run then weigh yourself after. The difference is the amount of weight you lost by sweating and you need to figure out how to get that back in. So if you lost one pound on your hour long run you need to hydrate appropriately by drinking 16 oz of water per hour. Make sense? This is a good way to feel it out. I think it is safe to say that upwards of 75% of the general population are dehydrated. A lot of people mistake thirst for hunger as well. Drinking more water has been very effective for many people as a simple way to lose weight. So drink up! You will feel better and perform better which will make you stronger and healthier.