I have personally had to work through this concept...

When in deep ketosis I was experimenting with various types of protein supplements and (surprisingly) found whey would spike my insulin. Of course this seemed odd as my supplement was pure and contained no sugar/no carbs.

After researching come to find out this is well known and in fact whey has a bigger impact on insulin levels than pure glucose. Apparently the amino acids in whey trigger insulin secretion directly in pancreatic beta cells.

Edit:

I thought it kind of funny doughnuts made its way into your fat/protein list and not the carb list.