Final answer:
Heavy individuals typically have higher Basal Metabolic Rates (BMR) due to the greater amount of energy required to maintain larger body sizes and the increased body surface area. Genetics and body composition also contribute to variations in BMR, with factors like exercise increasing BMR by building lean muscle mass.
Step-by-step explanation:
Heavy individuals often display a high Basal Metabolic Rate (BMR) because BMR increases with body size. The reason behind this increase is that larger bodies require more energy to maintain basic physiological functions. An increased body surface area usually ties in with a higher BMR since tall and thin individuals - who have more surface area relative to their mass - also tend to have higher BMRs. Contrary to common misunderstanding, obese individuals have a 25% higher metabolic rate than those who are thin, given the energy required to maintain a larger body mass.
Furthermore, body fat percentage affects BMR, where a lower body fat percentage typically results in a higher BMR. This is another factor contributing to the higher BMR in males on average when compared to females. Lastly, genetics play a role in determining BMR, with some racial groups having a naturally higher or lower BMR, which could also be influenced by dietary habits and living in different climatic conditions.
Thus, body size, surface area, and composition, as well as genetics, factor into why heavier individuals may have elevated basal metabolic rates. Lifestyle choices such as regular exercise can further augment BMR by building leaner muscle mass, which is more energetically demanding than fat tissue.