Final answer:
The concept of internal signals spontaneously regulating body weight by adjusting food intake is called the set-point theory, which is a form of negative feedback loop involving hunger and fullness signals.
Step-by-step explanation:
The concept that an internal signal regulates body weight by spontaneously adjusting food intake is known as the set-point theory. This theory suggests that each individual has a genetically predetermined ideal body weight, which is resistant to change.
The body spontaneously adjusts food intake and energy expenditure to maintain this set point. When our hunger signal is triggered, we eat until a sense of fullness signals us to stop, thereby regulating our weight. This regulation process is an example of a negative feedback loop, where the stimulus (hunger) changes direction in response to a signal (satiety).
While the set-point theory is a straightforward explanation for body weight regulation, it has limitations such as the lack of accounting for variations in metabolism and the influence of social and environmental factors. Additionally, empirical evidence suggests that metabolic rate does not necessarily change in response to significant weight loss, challenging some of the assumptions of the set-point theory.