There can be various factors that contribute to the differences in body weight, body mass index (BMI), and muscle mass among individuals who exercise and those who do not. It’s important to consider that:

1. Genetic factors: Genetics play a significant role in determining an individual’s body composition, metabolism, and weight distribution. Some individuals may have a genetic predisposition to naturally maintain a healthy body weight and lower BMI, regardless of exercise levels.

1. Caloric balance: Weight management is influenced by the balance between calorie intake and expenditure. While exercise can help increase energy expenditure, if individuals who exercise consume more calories than they burn, it can lead to weight gain or a higher BMI. On the other hand, individuals who do not exercise but maintain a balanced calorie intake may maintain a healthy body weight.

1. Muscle mass and composition: Exercise, particularly resistance training, can lead to an increase in muscle mass. However, muscle is denser than fat, which means that even though individuals who exercise may have higher muscle mass, it doesn’t necessarily translate to a lower BMI. BMI is a ratio of weight to height and does not differentiate between muscle mass and fat mass. Thus, individuals with higher muscle mass may have a higher BMI.

1. Body composition: Body composition, the proportion of muscle, fat, water, and other tissues in the body, varies among individuals. People who do not exercise may have lower overall body weight due to less muscle mass, but they may have a higher percentage of body fat. On the other hand, individuals who exercise may have a higher body weight due to increased muscle mass, which can contribute to a higher BMI, but they may have a lower percentage of body fat.

It’s important to note that BMI is a useful tool for assessing population-level trends and health risks, but it has limitations when it comes to individual variations. Body weight, BMI, and overall health should be evaluated in conjunction with other factors such as body composition, physical fitness, and overall well-being.

It’s also worth mentioning that regular exercise offers numerous health benefits, such as improved cardiovascular health, enhanced metabolism, and increased strength and mobility, regardless of its impact on BMI. The focus should be on overall health and well-being rather than solely relying on BMI as a measure of fitness or health status.