Hi my son is 3 year old his weight is 11.5 and his words are not so clear .can u help me with dis two issues

You should eat everything in moderate quantities. Try to keep your hands off oily and sweet food items. You can go through our blog to get extensive details about the diets you can try. https://www.credihealth.com/blog/low-carb-indian-diet/

Don't skip meal in fact take small and frequent meals at regular intervals to lose fast. 

if your son has started speaking monosyllables, it is an okay start. you need not worry. any other learning disability that you know off?