dementia. finding city participants who were underweight have a 34% increased risk of developing dementia. if you were severely obese, you had a 49% reduced risk. talk to us a little bit about this, why would this be that if you were slightly underweight, you would have a greater propensity for dementia. first of all these are pretty startling findings. they really contradict some previous studies looking at weight and your risk of dementia. in this study they found bmi under 20 actually had a significantly increased risk for dementia. tell us about that. if you re under 20 bmi, how underwait weight are you? right now we talk about a bmi of 18 as being really underweight. 20 is closer towards the normal range but it is under average for your height. what s even more surprising, those who were obese and swir