ConnectIQ doesn't provide a way to alter any profile or device settings at this time. The application can maintain a set of it's own data (available only to the application in the object store) and with the new FIT recording feature you'll be able to record some additional information into your activities but that won't link to any Garmin Connect elements.
I dont want change the weight in the user profile settings. I want to add the body weight measurement to the weight history that it is displayed in the chart view in my garmin connect account. Is there a way to do this?
There is now a App which provides uploads of health data to Garmin Connect.
Have a look at Record Weight & Blood to Garmin Health