Heavy sweating at unexpected times, such as sitting on the couch and watching a movie or walking on a cool day, is a possible symptom of diabetes, according to WebMD. Known as hyperhidrosis, this condition is also a possible symptom of thyroid problems or an infection, or perhaps just obesity.
Sweating more than other people after a workout or when the surroundings are hot is generally not a sign of a medical condition. When the body's work level increases and temperature elevates, sweat is the mechanism through which the body cools itself. Different people have different levels of perspiration, reports WebMD.
Hyperhidrosis takes two forms: localized and generalized. The localized variety (primary focal hyperhidrosis) is more common, affecting 1 to 3 percent of the general population. Most people notice the tendency beginning in childhood or the teen years. It does not lead to illness, and it is not a symptom of a larger problem. It usually affects just certain body parts, such as the groin, underarms, head or face, and the cause is unknown as of 2015 but could stem from a minor nervous malfunction, notes WebMD.
The generalized variety (secondary general hyperhidrosis) causes sweating on the whole body. One obvious sign is excess sweating all over the body at night. This type of excessive sweating is a sign of a deeper medical problem. In addition to diabetes, other possible causes include menopause, pregnancy, alcoholism, thyroid issues, and cancers such as lymphoma and leukemia, according to WebMD.