Rahul exercises regularly by visiting a gymnasium. Of late,he is gaining weight. What could be the reason? Choose the correct answer and elaborate.
$A$. Rahul has gained weight due to accumulation of fats in the body.
$B$. Rahul has gained weight due to increased muscle mass and loss of fat.
$C$. Rahul has gained weight because his muscle shape has improved.
$D$. Rahul has gained weight because he is accumulating water in the body.

(B) The correct answer is $B$. Regular exercise,such as weight training,leads to hypertrophy of muscle fibers.
When an individual exercises regularly,the volume and size of the muscles increase due to an increase in the amount of sarcoplasm,the number of myofibrils,and the density of mitochondria within the muscle cells.
While fat mass is typically reduced through consistent physical activity,the overall body weight may increase because muscle tissue is denser and heavier than adipose (fat) tissue.
Therefore,the weight gain observed in a person who exercises regularly is primarily due to the development of lean muscle mass rather than fat accumulation.