Hi Nadja,
Does Theo have all his teeth yet, or is he still to cut his 2nd year molars? Teething these can cause a huge problem with eating as it can really hurt them to chew, even soft stuff

If teething is an issue, try giving pain meds 20 min before mealtimes.
It's not ideal to have to distract them with TV / books / iPad etc during meals as that can become a prop that you will struggle to get rid of later!
We have also found that DS wasn't making the connection between feeling hungry and needing to eat... it's obvious to us adults but it isn't to some toddlers

We've been really working on helping him to see the connection and it's helping. Last week he was getting so hungry and completely melting down to the point where I had to force a few spoons of mush into his mouth before he realised it was making him feel better - only had to do this on 2 separate occasions thank goodness, then he realised he needed to
eat when he got hungry and upset

Of course the main problem with toddlers is getting them to stop playing and come to the table... they can be much more interested in toys than food at this age, another one of those lovely developmental stages

Don't worry too much about quantities eaten if his weight and height are stable and following his curve - they seem to be able to live on air! DS has for the last 3 months until the end of cutting his 2nd year molars, but has still managed to grow and need bigger clothes

HTH
