India, Sept. 3 -- Two people can be the same age and follow seemingly similar lifestyles, yet have very different body compositions. While genetics often gets the credit for these differences, muscle mass could be one of the key factors shaping how the body ages.

"Look carefully, on the left side are average Indians. Same age, so-called, we eat at home, we don't eat outside, we eat healthy. Honestly, in our house, everyone will meet like this," said Dr Ravi K Gupta, US board-certified oncologist, in his September 1 Instagram post. (Also read: Woman who lost 32 kg shares 5 non-negotiables that helped her lose weight from home: 'Stop skipping meals' )

He pointed out that even among people of a similar age, differences in physical appearan...