Question

Discuss one factor that influences resting metabolic rate in humans. Please just discuss one factor that affects RMR. I want some depth to the content without going into details about lifestyle changes (that will be up to your peers to discuss in their replies).

Link: https://www.cbsnews.com/news/dont-blame-your-metabolism/

Answer 1

Secretion of Thyroid hormone (T₃ and T₄) increases resting metabolic rate in humans When the thyroid gland secretes maximal amount of thyroxine( T₃ ), the metabolic rate sometimes rises 50 to 100 percent above normal. On the other side, total loss of thyroid secretion decreases the metabolic rate to 40 to 60 percent of normal.

Mechanism of Action: Thyroid hormone enter cells and T₃ binds to TR in the nuclei. T₄ can also bind, but not as avidly. The hormone-receptor complex then binds to DNA via zinc fingers and increases the expression of variety of genes coding for proteins that regulate cell function.

Effects on resting metabolic rate: T₃ and T₄ increases O₂ consumption due to metabolism of fatty acids they mobilize in metabolically active tissues. Also, thyroid hormones increases the activity of membrane bound Na⁺- K⁺ ATPase in many tissues.

When the metabolic rate is increased in adults, nitrogen excretion is increased; if food intake is not increased, endogenous protein and fat stores are catabolized and weight is lost.

When the metabolic rate is increased, the need for vitamins is increased and vitamin deficiency syndromes may be precipitated.

Adaptation of the thyroid gland- with increased secretion in cold climate and decreased secretion in hot climate- contributes to differences in resting metabolic rate among people living in different geographical zones; for example, people living in arctic regions have resting metabolic rate 10 to 20 percent higher than those living in tropical regions.