The problem of unhealthy diets and growing overweight, obesity and diet-related diseases (e.g. diabetes, hypertension…) in the UAE and neighboring States;

May I suggest that you read these documents in the following order:

1-the report of the WHO Commission on Ending Childhood Obesity (2016): this report sets the tone of what States around the world should aim to do to help prevent child obesity
2- the report my supervisor wrote with some Liverpool colleagues for Unicef (2018): this report aims to frame the problem of child obesity and food marketing more specifically as a children’s rights issue
3-the Lancet Commission report (2019): this report further raises the alarm on the need to tackle all forms of malnutrition for human and planetary health
4-the EMRO nutrition strategy (2010-2019): you should check the latest documents available relating to nutrition on the EMRO website too
5-the EMRO technical report on nutrition (2017)
6-the report on food marketing I wrote following a project running from 2013 to 2018 (2018)
7- the note following the regional committee meeting on obesity in the EMR (2018)
8-the Unicef advocacy brief on healthy food environments (2019): published for the 30th anniversary of the Convention on the Rights of the Child

Once you have looked at these references and done further independent research (the documents refer to a wealth of interesting references), perhaps you can draft a five- or six-page proposal identifying:

1-the area you would like to research during your PhD studies
2-why you think this topic is of major significance
3-the research questions you have identified and would like your PhD to answer
4-why you think you are well placed to undertake this research