Brief Answer:
About a healthy life...

Detailed Answer:
Hello and welcome to 'Ask A Doctor' service...
I've gone through your query...

Well, first and foremost, it's advisable to measure your present body-weight, height, and waist circumference properly as appearing thin on the naked eyes doesn't carry any medical relevance...

To become healthy, you must adopt a healthy lifestyle first (irrespective of the age)...

These includes:
Eat and sleep in time,
Have mostly homemade foods,
Avoid fast/junk/processed foods,
A good night's sleep of 6-8hrs per day,
Not to take any unnecessary stress,
Not to indulge in any form of smoking/alcohol

Not to spend too long in front of the TV/computers, take frequent breaks
-whenever possible

Along with these, you should start freehand exercises, jogging for 30-40min daily...

Do get yourself examined up routinely by a physician and undergo routine health check-ups as and when required/advised...

All these will be helpful in improving lifestyle as well as maintaining a healthy life...

Take Care
Kind Regards

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