Is the world overpopulated?
That question is not easy to answer because there are too many variables at play. Even if I simplify human needs, the question is still tough. Let's pretend that the only thing that humans need is food, water, and shelter. Also, for the sake of argument, let's round off the world's population at 7 billion. There is definitely enough habitable space on planet earth for 7 billion people to safely occupy. So shelter isn't a limiting factor . . . yet.
Food isn't an issue either. The world currently produces enough food to feed the entire human population. The following is from worldhunger.org
The world produces enough food to feed everyone. For the world as a whole, per capita food availability has risen from about 2220 kcal/person/day in the early 1960s to 2790 kcal/person/day in 2006-08, while developing countries even recorded a leap from 1850 kcal/person/day to over 2640 kcal/person/day. This growth in food availability in conjunction with improved access to food helped reduce the percentage of chronically undernourished people in developing countries from 34 percent in the mid 1970s to just 15 percent three decades later. (FAO 2012, p. 4) The principal problem is that many people in the world still do not have sufficient income to purchase (or land to grow) enough food.
If the entire world turned to altruism, nobody would die from hunger.
Lastly is water. Fresh water is an issue in a lot of places. A person could argue that there isn't enough fresh water available for the human population. If that is true, then yes, the world is overpopulated. Water is a limiting factor to the human population. Of course, if somebody discovered a way to cheaply and easily desalinate ocean water, then fresh water would no longer be the most immediate limiting factor for the human population. We have the ability to desalinate right now. It's expensive and energy intensive, but it is possible.
If you forced me to answer yes or no to your question, I would say "no." No, the world is not overpopulated. But it's getting there very quickly. NBC ran a story about this same topic last night. The "expert" that was on predicted the year 2050. That lines up with predictions that I was told during a world hunger/world poverty class that I took 10 years ago.