Weight regain within one year after weight loss is frequently observed and is referred to as yo-yo dieting or weight cycling. In this study, we explore the effects of yo-yo dieting on the liver, adipose tissue, and muscle characteristics of male zebrafish. Four-month-old AB wild-type male zebrafish were randomly assigned to three groups: high-calorie intake (H, seven meals per day), low-calorie intake (L, two meals per day), and yo-yo diet (the low- and high-calorie alternation switched every two weeks) groups. Feeding the fish the H diet for over 8 weeks led to steatosis and damage to the liver. The yo-yo diet reduced liver lipid accumulation at week eight but caused a similar degree of lipid accumulation as the H diet thereafter. It was found that twenty weeks of yo-yo dieting actually exacerbated hepatic damage. Compared to the L diet, feeding the fish on the yo-yo and H diets for a period of 20 weeks significantly increased the size of muscle fibers, resulting in higher speed during burst swimming and a significant increase in the size and number of adipocytes in the abdominal tissue. To summarize, short-term yo-yo dieting was found to attenuate hepatosteatosis and maintain fast-twitch muscle function. Long-term yo-yo dieting preserved fast-twitch muscle function and muscle fiber size; however, it exacerbated the pathological changes in the liver.
Keywords: exercise; hepatosteatosis; high-calorie intake; muscle performance; weight cycling; zebrafish.