Metabolic functions are at their peak in the morning; if you eat very little then, the body will think, "there's not enough to eat today-I'm afraid I'll be hungry." As a result, there will be an automatic slowdown in metabolism in the interest of self-preservation.
早上代謝功能最旺盛時，如果吃得很少，身體會誤以為「主人今天食物不足，恐怕要餓肚子」，於是自動降低代謝量以求自保。