Posted by Scott Kirsner December 14, 2009 07:00 AM

If you feel that most messages posted on Twitter verge on over-sharing, you can stop reading here.

But if you’re fascinated (as I am) by all the private-turned-public observations Twitter encourages, the WiFi Body Scale from Withings, a French company, will be just one more astounding data point. It not only charts the ups and downs of your body mass index on a password-protected Web site, but it can send out info about your morning weigh-in to all your followers on Twitter.

Yes, it tweets your weight.

It went on sale in the U.S. in September, and entrepreneur-turned-investor Bob Metcalfe of Polaris Venture Partners was one of the first locals to start using it. (The Twitter feature was added just last month.)

Every morning at 9 AM, the scale in Metcalfe’s Back Bay townhouse sends out a tweet; he’s trying to go from the 220-pound range to 179, by eating less and exercising more. A typical message might read, “My weight: 222 lb. 41.2 lb to go. Never too rich or too thin. http://withings.com.”

Soon after I started seeing messages from Metcalfe’s bathroom appliance, I noticed thatRich Miner, the Cambridge-based partner at Google Ventures, the investment arm of the search company, was sending out a tweet right after Metcalfe’s. A characteristic Miner tweet would say, “My weight: 168.7 lb. 16.7 lb to go. How obnoxious is this…  http://withings.com.”

Read more about this body weight story here