I am working on a presentation I will give later in the month at the University of Alabama Medical School on the economics of obesity. To put things in context, I wanted a graph showing the average weight of US men and women over the past 40 or so years. If you think it would be easy to find this information on the web, you'd be wrong.
There are lots of studies reporting the percent obese or reporting the mean BMI for a couple years, but the CDC, for some reason, hasn't complied a simple data set that lets you compare in the same units (their publications sometimes report means, sometimes medians, sometimes BMI, sometimes weight in lbs) for consistent age ranges. After several hours work, I finally cobbled together the graph below showing the average weight (in lbs) of men and women from about 1960 to 2010 for people aged 40-49 (if you want to check me, the data was obtained from the publications here, here, and here, all of which rely on National Health and Nutrition Examination (NHANES) Survey).
Is it what you expected? From about 1960 to today (or at least the latest comparable data I could find), the average weight of men aged 40-49 has increased 31.5 lbs. For women, the number is 27.2 lbs. In the past 10 years, the average weight of men aged 40-49 has increased 4.6 lbs. For 40-49 year old women, weight actually fell 0.2 lbs over this time period. In the last four years, the average weight of men in this age rage actually went down 1.7 lbs and the average weight of women fell 3.3 lbs.
It is also worth mentioning that the average 40-49 year old male is today 1.3 inches taller than he was in 1960. The average women is a full inch taller as well.
Whether these changes in weight are large or small are a subjective judgement call. I will only point out that the average 40-49 year old women today weights about the same as the average 40-49 year old man from 1960.