Face is exposed to outside climate, UV and other light rays, that is why it is slightly darker when compared to your chest area. If you come to ideal weight it will be beneficial for your skin health also, but if you become over weight there will be insulin resistance, acanthosis nigricans, appearance of stretch marks,....
Next Steps
Regular use of sunscreen with spf 50+ once in every 3-4 hrs, Night face serum and or MOISTURIZER, you can go for chemical peeling session by Consultant Dermatologist
Health Tips
Regular use of sunscreen as well as sun protection in the form of caps, hats, umbrella,, maintain proper hydration, regular exercise and maintain healthy ideal body weight