Reasons for thinness

Reasons for thinness

Some common reasons why a person may find it hard to gain weight include:

• Genetics 

Genetics is the study of genes, heredity, and variation in living organisms.It is generally considered a field of biology, but it intersects frequently with many of the life sciences and is strongly linked with the study of information systems. http://en.wikipedia.org/wiki/Genetics

• Not eating enough

• Having a very physically active lifestyle or job.

• Overexercising.

Source 

http://www.betterhealth.vic.gov.au/