Whether you're sharing food or knowledge, both make you useful to the society.
You don't always need to have an excess of something to share. You just need the will to do so.
Take the world's leading developer forum for an example. StackOverflow houses useful answers to hundreds of thousands of interesting questions. All of which are contributed by people like you and me.
Why do people go over there to answer someone's question?
It's not because they have too much of free time or they want to show off. It's because they want to give back to the community. Help people code better and faster.
I'm not a frequent poster of the forum but I try to fulfil my share of contribution to the community by writing articles that help people overcome roadblocks.
Learn to share.
It's not always about taking. When you start giving to the society, be it knowledge, money or food, you get back the same love with interest when you need it the most.
Be helpful. More importantly, be useful. Share.