The nutrition style of the Prophet, sallallaahu 'alayhi wa sallam
5-9-2011 | IslamWeb
Question:
Dear sheikh assalamualaikum! I want to know how may meals did prophet muhammed eat? does he take snak food? what is our nomal stomoch size, in order to find 1/3 of it. now a days it's difficult to select healthy food. even fruits & vegies also full of chemicals.. even the honey is sugarly syrup like.. how to look after our children with healthy food? how to keep healthy? please answer,it will benifit lot of us. Jazakallah Khair.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
The Prophet used to eat from what was available to him, and there is nothing reported in the available books of Sunnah - after investigation - about how many times he used to eat food, in case he had food.
Ibn Al-Qayyim 
clarified the guidance of the Prophet regarding eating food in his book “Zaad Al-Ma’aad [Provisions for the Hereafter]”. If you can read Arabic, then you may read this book or read its translation if it is available as it is very beneficial.
Ibn Al-Qayyim said in this book: ''He used to eat whatever was available to him and if he did not find some food to eat, he used to be patient to an extent that he used to tie a stone to his stomach due to hunger, and three consecutive crescents (i.e. lunar months) would be seen without there being a fire lit in his house to cook food.”
As regards estimating the size of one-third of one’s stomach [i.e. one-third of what he/she would have to eat his/her fill], then this differs according to the difference of persons as they may differ in the amount of food that they need.
In any case, a Muslim should not be extravagant in eating food as this may be harmful to his religion and to his worldly life. For more benefit, please refer to Fataawa 7372 and 85392.
Also, you may benefit from trustworthy experts in nutrition and seek their advice about suitable food for everyone and especially for children.
Finally, it should be noted that one should avoid whispers about food as this may lead to many disadvantages.
Allaah knows best.