Originally posted in another thread but I thought I'd post this particular bit here so I can get feedback on this specific issue.
Food:
This is not part of the game, but I'll explain how the present farm structures could be enhanced to make it part of the game. In turn it will help alleviate this problem of unhindered early over-expansion. Presently, farming only serves to increase the population cap and does not affect the maintenance of keeping your population alive. So you can have a colony with 10 billion people and not have a single food producing structure. It would have been a better way to keep population growth and expansion in check. To make your population grow you need to be able to sustain them and this is where upkeep comes into play. I think this is the root of the problem and fixing this would help to make expansion more realistic. Farms are already in the game so it's just a matter of expanding their purpose and capabilities.
Let's say that each .1 Billion (100 Million colonists) require .1 Billion food units per turn. A number will indicate how much food you are making each turn on this planet. Perhaps the more you invest in social work the more food that is created based on the number of farms on the planet. A green number with a + next to this could represent the amount of surplus you are making. A red number with a - would indicate the deficit on the planet.
A new colony without the food structure should automatically start in the negative and require external support till it is established. A well maintained and established colony would most likely be in the positive. If your colony is in the negative then it will require external support in order to maintain. If you ignore your population at .1 for too long we'll assume they starve or scatter dissolving your colony. Your colony will then disappear from the map.
The food will need to come from within or from outside the colony. The logical way to go about it would be to have to build farms which would require investment and time to put in place as they do now. Farms are already in the game, so why not just make them dual purpose or expand their purposes? Until enough farms, and enough labor to run the farms are in place, you will have to receive support from your other colonies by way of transports delivering supplies. This would make a viable strategy for your opponents to thwart your efforts to bite off more than you can chew. In order to keep your quickly acquired colonies you will need a large fleet to support the transports in route. At the beginning of the game you don't have the means to research, create fleets, and construct structures, all at the same time. This will be an automatic limiting mechanism. What better way to limit things than by having the enemy AI's thwart your efforts of holding onto scattered and fledgling colonies? Eventually, with the right technology, you won't need farms for food and will get much more efficient at creating energy.