Another possibility is that your first measurement could have been off. BF% increase without BW going up it sounds strange to me. Also, this client needs to be training at least 2x/week if not more. Is she Type 1 or 2 diabetic? Since she is diabetic, I would suggest training more often will help her with a better blood regulation and better A1C levels. Not seeing her often, gives her the time and excuses not to follow any instructions you might have given her and make it easier for her to lie about her diet, exercise and other habits and changes she is trying accomplish. Have you taken her measurements since then?
I am confused.
Her bodyfat went up, as tested several times, but her weight did not change. Have I got that right?
This tells me that her muscle mass went down percentage wise. Using tubing and bands may not be enough to sustain her muscle mass, especially only once a week. ACSM recommends miniumum of 2x’s a week. Have you considered revising the strength training program?
Each bio-electrical impedance device comes with a manual that explains the proper conditions under which to get an accurate read on a client. Most differences that you’re describing, are due to a dehydration issue. It could be that with the summertime heat and humidity (not sure where you are located?), her normal water intake needs to be increased to account for these issues. The same could be true if she was traveling recently, or even is there was a change in the medication she’s been using to control her diabetes.
As Karin, indicated, it would be unheard of for her body fat percentage to make a jump like that without her weight also climbing. Did you also take measurements? I use measurements, as well as a bio-impedance scale to double check all my assessments and to decrease the chances of a dehydration issue. The tanita scale I use, also tests for hydration level to see the accuracy of the body fat reading and see where dehydration may be an issue.
If you don’t have measurements on her, I would take measurements and see if the body fat percentage you get with measurements is equal to what you saw with the scale and then go from there.
I’m not sure if you are aware but bioelectrical impedance device has +/- of up to 14% depending upon if your client is hydrated, has jewelry on, or isn’t holding the device appropriately. Maybe BF% isn’t the best way to measure if it will be discouraging. I would look into other ways of measuring her progress such as doing body measurements, whether it’s hip to waist or measuring bust, waist, hip, arms, and thigh or doing a fitness assessment (3 minute step test, push up/modified push up, measurements, and flexibility).
Hope this helps!