The development of large breasts in males, commonly referred to as 'Man Boobs' which may be due to a medical condition, and not just obesity.
While this is the accumulation of breast tissue, there are many underlying causes.
It can come from a hormone imbalance.
Over eating can lead to fat tissue being generated in the breast area.
Use of drugs such as excessive amounts of pot, steroid use.
Ingestion of estrogens, from the water supply, over time.
Body building, in which the exercises are to enlarge the breast area is not considered Gynecomastia, unless steroid use is involved.
From a childhood condition.
From ingestion of foods, that have assorted hormones injected into them, mainly though Chicken.