To remind your friend to take care of their body, you can say:

"Remember to take care of yourself."
"Don't forget to look after your health."
"Make sure you're taking care of your body."
"Pay attention to your physical well-being."
"Don't neglect your self-care."

You can also offer specific suggestions, such as:

"Make sure you're getting enough sleep."
"Don't skip meals or eat unhealthy food."
"Exercise regularly to stay fit."
"Drink plenty of water and stay hydrated."
"Get regular check-ups to monitor your health."

By reminding your friend to take care of themselves and offering practical suggestions, you can help them maintain their physical well-being.