In the app, please click on the current photo in the section Me (the icon showing a profile in the tab bar) and then either choose the source of the new image or take a picture and save it.
When you have created your Lifesum account using Facebook the Lifesum app automatically shows the profile picture you are currently using on Facebook.
If you have created your Lifesum account using an email or Google+ and would like to show your Facebook profile picture in Lifesum, please go to your Settings and scroll down to Facebook and click on Connect. Lifesum will then automatically show the Facebook profile picture.
When using Facebook: In order to change the profile picture in Lifesum you need to change the profile picture on Facebook.