Humans do have their different smells due to the different body chemistries we carry. Some humans have foul odors while some smell really nice. The people who smell worse than others do so because their sweats contain lower amounts of salts. This gives bacteria the convenient environment they need to create very foul-smelling acids. Obese people sweat profusely. People who often take spicy foods also smell worse than others. Certain medical issues such as diabetes can also alter the natural body and sweat chemistry, which consequently results in body odor. Some drugs also contain certain side effects that can give rise to body odor.
However, this is not only applicable to Indian nationals – even people from some Arab nations do eat loads and loads of spices so they could be expected to have some unique smells as well, which could be either good or bad.
But in all sincerity, I agree with people who say "Indians smell because they don't use deodorants". Perhaps Indians who have had embarrassing odors mostly are the ones that never used deodorants or body sprays.