Answer:
The short answer: choosing foods wisely means choosing foods that your body can use to help you preform daily activities better as well as to feel better. In the same way that we do not feed zoo animals donuts or other "human food" because it will make them sick, it can also make people very sick over time. Many diseases called "lifestyle diseases" can often be prevented by making wise food choices. These diseases include diabetes, some types of cancer such as colon cancer, heart disease and obesity as some of the most common.
Consciously choosing healthy foods probably means that you care about your body or your health, which means you are also more likely to exercise and get enough sleep. Also, by eating healthy foods you are more likely to have better energy levels and feel like exercising and being more active.