havinghadamoment
Yes, there is actually - at the moment - enough food for everyone on the planet, but it's not just about food though, is it?
In an ideal and fair world, the UK would be living on food that is grown here in this country - and other countries would be doing the same, too. That would actually make some poorer countries a lot better off than the UK, which relies heavily on others to produce it. So if we were heading that way, it would just be obvious, that we need less mouths to feed here in this country.
And yes, enough food is being produced to feed the world, but the Western Standard of Living is not just about food really, is it?
It is about electricity, running water, infrastructure, transport... all this (and more) is needed for economic development. The above is a lot more difficult to deal with than food alone because the main source of energy (fossil fuels) is finite. Yes, there are renewable sources, but they are at an early stage, and do not account for much of the energy production. They are also very unlikely to be able to replace fossil fuels. Nuclear fusion would really be the answer to this, but given that people already get worked up by the thought of nuclear power plants alone, I'm not sure they would want anything else with the word "nuclear" attached to it.
With regards to water - yes, we have a lot of sea water around us. This is not freshwater though, it needs desalination for us to be able to drink it. This goes back to the previous paragraph - because that process wastes a lot of energy...
So there's more to this than just food.