Here's an article from Jeff Nelson on vegsource.com on his recent research on nuts. This was motivated by the article about Chef AJ a few weeks ago where she lost weight by cutting down the nuts.
I think the people most affected by this issue are older women because we have the lowest calorie intake needs. When we eat an ounce of nuts a day, it is a significant source of fat in our diet, and it squeezes out more satiating foods such as potatoes. And with our lower calories needs, do we really need a full oz? I prefer 1/2 oz or even lower.