The fact of becoming fatter or heavier.
Weight gain occurs when energy intake exceeds energy expenditure. Many factors can affect either energy intake or expenditure and produce increased body weight. Some athletes desire weight gain for improved performance, while others prefer to avoid weight gain. Most often, athletes wishing to gain weight are interested in adding lean body mass. Other athletes, such as sumo wrestlers or perhaps football linemen, may simply wish to add extra pounds and may or may not require increased lean body mass concurrently to achieve their goals.