Correlation with control group

Sorry if this is a very basic question.

If you have two groups: diseased and control. Both groups undergoes an intervention giving you two time points (before and after).

Say you measure weight and glucose uptake at both time points, and want to correlate the change in these variables.

How do you correlate the change in weight and change in glucose uptake after intervention in the disease group, while compensation for the change in the control group?

Thank you very much and merry christmas!
Thank you for your reply, I have looked through the links.

Still, I cant quite catch how to precede, do you mind elaborate?


Group Disease Change in Weight Change in Glucose Uptake
Participant 1 2 -9
Participant 2 3 -8
Group Control
Participant 3 8 2
Participant 4 7 1

And if I for Group Disease get with Pearson Correlation R^2=-0.8 and P = 0.3
And for Group Control I get R^2=0.7 and P = 0.4

This is not what I want. I can see that the correlations are different (negative vs positive), how do I "use my control group"?
I want to adjust for the changes I see in the control group, and based on that, look at the correlation between change in weight and glucose uptake in diseased group.

Im I far of, or just ignorant?

Thank you very much!