Most diseases, including obesity, can be traced back to a gene or a set of genes. The linkage between the ob gene and leptin hormone is now widely understood. Leptin is known to send a trigger to the brain that tells the individual that ‘I am full, I don’t need to eat more.’
The relationship between genes and cancer has also been discovered. Though, genetic causes do not necessarily lead to the emergence of either obesity or cancer in an individual. External environmental factors are a more potent cause of obesity.
The Centers for Disease Control and the www.worldobesity.org mention three critical factors that play an essential part in the development of obesity. These are:
The environment plays a crucial role in shaping our habits and lifestyle. Availability of motorized transport at home, convenience foods, and home entertainment solutions are some factors that determine the low expenditure of energy.
Genetics, too, has a role in obesity. Genes can cause disorders resulting in obesity.
Prevention of obesity starts in childhood. Lower birth weight seems to be associated with later risk for central obesity. It confers increased cardiovascular risk, which is probably occurring through changes in the hormone systems. (Oken et al., 2003)
Body composition changes with aging due to several factors ranging from physical inactivity, diet, hormonal changes, etc.
You can get an overall perspective of obesity and how natural solutions can help contain this disease here.