As soon as you begin weight training then you need to stop weighing on the scales and go by how your clothing is fitting or how you look because your muscle mass will increase causing an increase on the scales. Most beginning weight trainers, will increase their muscle mass immediately and also lose body fat at the same time which would mean the scale weight would be the same or greater. For intermediate or advanced trainers body fat testing is a valuable tool to access how the body is reacting to new supplements that have been introduced or new training programmes started . To have an accurate record of your progress you need to have your body fat readings recorded by an experience person with calipers. Body fat recordings are done over a number of sites plus there are a number of charts available to work the formula, so a certain number of sites need to be taken for a particular chart. The result of the total of the caliper measures enables us to work out the fat mass ( how much fat is on the body) and the lean mass (the organ, blood, bones, skin + importantly muscle). When we diet the former 4 do not change so we know any ups or downs must be muscle gained or lost. Ideally the lean mass would be increasing each measure , and the fat mass will decrease. The scale weight is irrelevant as it is only a tool we use to get the final figure of fat mass and lean mass. How often should you be tested For a beginner I say fortnightly and for more advanced 6 weekly before programme changes