Noted the history about your 3 year old daughter who is 11 kg only but otherwise active.
She does not want to eat. Take a few bites or sips.
There can be problem in the esophagus
, stomach or small intestine
Hence I would advise you the following:
Contrast studies for esophagus stomach and small intestines.
High resolution ultrasonography
and CT scan if required.
Tests of blood, urine and stool.
There may be worm infestation. So give dose for worms.
Consult a Pediatric Surgeon for clinical examination, correlation with reports and treat her accordingly.
Also look for the foods and beverages that shew likes as it is possible that she is not developing taste for certain foods. This is also a common problem.
There can be attention problem, talk to your Pediatrician
and proper symptomatic management.
Hope I have answered your query. Let me know if I can assist you further.
Dr. T Chandrakant,