I came across this banana muffin recipe that uses no butter or oil and is fairly low in sugar. It's pretty good despite the lack of fat. #cookingathome 

The fat comes entirely from yogurt and egg; banana provides moisture and additional sweetness. They'll last a few days in an airtight container but will get a little dry on day 3. I think you can revive them if you warm them up but I haven't tried that.

I've baked three batches so far.
1st batch: I halved the recipe but didn't bother cutting the egg in half, so I basically doubled the amount of egg. The result was denser but soft and moist. I probably should have reduced the baking powder.
2nd batch: Mixed the full recipe using an extra large egg. Baked half the batter right away and ended up with a lighter and fluffier muffin. It baked well in the counter top oven.
3rd batch: As an experiment, I froze the other half of the batter and baked it two days later. They were good to eat but deflated while baking. Conclusion: you shouldn't freeze quick bread batter.

NOTE 1: Comments warn that these will stick like crazy to paper liners so I used silicone muffin cups and they release cleanly.
NOTE 2: I don't believe in nonfat anything. The yogurt I used is 3% fat and I think it helps.
NOTE 3: I added 1/2 tsp cinnamon.
NOTE 4: If you care about this sort of thing (and I really don't), each muffin is 83 calories. Even my double egg version is around 90 calories.

Recipe is here - http://recipes.sparkpeople.com/recipe-detail.asp?recipe=359129

I've got a tub of yogurt to use up so I'll probably test a few more recipes.