Readings can be greatly affected by variables like
hydration levels (
since water also conducts electrical impulses), meal times (a recent meal can skew results), and workouts (taking a reading directly after exercise leads to a lower body fat reading).
That might look good on your scale, sure, but it's bad news for your
hydration levels, says dietitian Jaime Mass, RD. Plus,
since whole carbs such as oatmeal, whole grain pasta, and brown rice all soak up water during the cooking process, eating them can actually increase your
hydration levels.