Japanese researchers say they have discovered a mechanism behind why people easily gain weight in middle age.

A Nagoya University research team led by Professor Nakamura Kazuhiro focused on proteins in neurons in the brains of rats called melanocortin 4 receptors, or MC4Rs.

The proteins receive information that a person is gaining weight as fat accumulates. They also send signals to stimulate metabolism and reduce food intake.
The primary cilia of MC4Rs function as antenna.

The researchers say their study shows aging and excess food intake shorten the antenna, making it difficult to send signals to promote metabolism.

They say the primary cilia shortened in rats that were fed high-calorie food. Meanwhile, rats fed low-calorie food extended the length of the primary cilia even after it had shortened.

They expect the results to help prevent middle-aged people from gaining weight and help develop new treatment for obesity.

Professor Nakamura says that by not consuming too many calories, people can promote metabolism and stay fit.