I knowingly lied to my patient
Why did you knowingly lie to your patient?
I wanted them to believe something that would make them change their lifestyle.
I hope that you know how you are going to present the truth then. It is going to be worse when they find out that you knowingly and willingly lied to them.
The lifestyle change is for their own good, they don't need to know the truth.
Honesty is critical in a doctor patient relationship. You should be truthful al all times with your patients because it's in their best interest to follow your honest advice. Find other ways to get them to do what you want them to do.