Aging, which is generally accompanied by a slower metabolism , often causes weight gain unless accompanied by a reduction in food intake or adequate exercise .
Weight gain is a significant symptom of several endocrine diseases.
It may also be caused by heart or lung disorders. A rapid weight gain may indicate dangerous fluid retention. There may be other causes of unintentional weight gain. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications.