BOSTON, Jan. 16 (UPI) -- A mathematical model may better explain how the body regulates weight -- and why it is so hard to lose weight, U.S. researchers said.
"There are problems with both of the current hypotheses for how the body balances energy intake and expenditure to maintain a stable weight," lead author Joshua Tam, a doctoral student at the Massachusetts General Hospital, said in a statement.
The study, published in Cell Metabolism, outlines a system in which there may be several steady states to which an animal's weight tends to gravitate, rather than a single "set point."
The well-known tendency for body weight to remain stable despite changes in diet or energy expenditure -- observed in both humans and other mammals -- led to the development of the "set-point" hypothesis, which holds that an individual's metabolism acts to oppose changes to a physiologically predetermined body weight.
However, opponents of the theory argue that a natural set-point would prevent the development of obesity in the first place. They say the body's weight "settling point" is determined solely by environmental factors, such as the availability of food, along with physical activity and other behavioral factors.
Opposing the settling point theory are study results showing that, if given access only to low-calorie foods, some animals will maintain their weight by increasing the amount of food they consume, supporting a tendency to return to an established weight.
