I don’t know where you got that from but, apparently lemon water is useful for reducing weight. Lemon juice has many health benefits and losing weight is one among them. If you are planning to try this, then I suggest you use honey instead of sugar. Make the lemon juice with lukewarm water and mix honey in it. Over a period of time you will see that this helps in reducing your weight. In the worst case at least it will help in maintaining your weight, even if you don’t lose any. I hope it works, let me know how it goes.