Google "why the scale lies" for some insight. If you ate too much sodium the scale can be up the next day from fluid retention. Your body is made up of 60% water so it fluctuates hourly. Sore muscles from exercise can make the scale go up. Medications, stress, hormones etc. can all effect the scale. Sometimes it could the kinds of foods you eat. If you know you are on plan, then just keep going. It will come off again and then some.