The emergence of meal replacement (MR) originates from physical exercise or fitness as a substitute for one or all meals and later expands to the field of weight loss. Indeed, the main application of current meal replacement is to lose body weight, whether patients with obesity, diabetes, fatty liver, infertile or pregnant women can benefit from weight loss. In addition, MRs still exhibit more biomedical potential in preventing and treating diseases, like anti-diabetes, improving fatty liver and kidney disease, preventing cancer, conceiving and reducing pregnancy complications, and improving life quality. Indeed, there are also disadvantages to meal replacement, including causing adverse effects, although most are acceptable and tolerated. To date, various commercially-developed MRs are walking from dining table to sickbed. Therefore, a scientific understanding of the advantages and disadvantages of meal replacements is crucial for their extensive application beyond biomedical potentials.