Clutter: another example

The following sentence appears in a physician bio I've just seen:

His main interests have focused on the role of insulin and the insulin-like growth factors in normal physiology and disease states, including obesity, type 2 diabetes, and cancer.

Please note that a main interest is always already (ie, by definition) an area of focus. Thus, you wouldn't want to describe main interests as focusing on this or that: instead, main interests include.

His main interests include...