Final answer:
The claim that protein supplements are the only way for men to gain weight during rehabilitation is false; a balanced diet with adequate energy and protein from different sources is also crucial.
Step-by-step explanation:
The statement that the only way the men could gain weight during rehabilitation was to consume a protein supplement is false. While protein supplements can aid in weight gain and muscle rebuilding, they are not the sole method. A balanced diet with adequate energy and nutrients, including protein from various food sources, is essential for weight gain and recovery from undernutrition. Protein supplements may sometimes contain amino acids like branched-chain amino acids or glutamine, but they can be inferior to whole proteins. Furthermore, care must be taken as some supplements may falsely inflate protein content through 'protein spiking'. It's important to consider the whole diet and not just supplements when aiming for weight gain or nutritional rehabilitation.