Final answer:
Adaptive thermogenesis occurs in response to fasting and cold exposure, as the body increases its metabolic rate to generate heat and maintain internal temperature during times of low external temperatures and energy scarcity.
Step-by-step explanation:
Adaptive thermogenesis refers to the body's mechanism for producing heat in response to environmental changes in temperature and diet. In the context of temperature and dietary conditions, adaptive thermogenesis occurs in response to both fasting and cold exposure. This is due to the body's need to maintain a constant internal temperature, which involves increasing the metabolic rate to generate heat when external temperatures are cold and food energy is limited.
The metabolism of brown adipose tissue is a key factor in non-shivering thermogenesis. Such tissue specializes in generating heat through metabolic processes. Fasting leads to a decrease in the metabolic rate as an adaptive mechanism during times of scarcity, which helps conserve energy. However, exposure to cold increases the basal metabolic rate (BMR) to produce the extra heat needed. This involves physiological responses such as shivering and the breakdown of stored energy to maintain the core body temperature.