Reinforce what they have done rather than what they have not done
I am also curious about the way this question was phrased, it’s not about sticking with you , it’s about their commitment to their goals and themselves.
Clients stay with you as long as they are getting value from your services
Stay on track with goal setting and re assessments
Maybe, depending on what you are noticing in their body image, they are gaining muscle.
One of my client’s has a goal to lose weight and get healthier. Well, after 12 weeks of exercise sessions with her , she says that her cholesterol has dropped , blood pressure has dropped and her clothes fit better, she feels better too, but no real change on the scale. She is moving forward and continuing to one hour exercise sessions with me instead of 30 minutes. This is always a work in progress. The scale is one factor in weight management, but as long as positive changes are happening, it may not be so much of an issue.