All of the following factors play a role in determining a person's weight:
- Heredity: Genetics can influence body weight and fat distribution.
- Activity level: Physical activity affects energy expenditure and can influence weight.
- Body mass index (BMI): While BMI itself is a measure (not a determining factor), it is used to assess weight relative to height and can indicate whether an individual is underweight, normal weight, overweight, or obese.
- Body composition: This refers to the proportion of fat and non-fat mass in the body, which can influence overall weight and health.
So, the correct selections are: heredity, activity level, body mass index (BMI), and body composition.