When narrowing down the topic, you may need to be more specific about aspects of your question. If we wanted to narrow the topic childhood obesity and technology, we may need to specify what we want to examine. All technology? Or a specific kind such as video games or social media? All children? Or a specific group?
Make sure that your topic fits the length of your paper or project. For example can you write a five page paper on all of climate change? No! It is far too big a topic for five pages. You will need to choose some subtopics within climate change to focus on.
If you are finding too few results, it may not be the topic. You may need to choose different keywords. Different synonyms, related words, and combinations of keywords will bring different results.