Comments:

1. Two different manuscript files (one without supplementary Figure 1) were accidentally merged during the submission. As a friendly advice, authors should check the final proof carefully next time to ensure that everything is present and correct.

2. The true purpose of this study, which I suppose, is to validate whether the elevated tripeptide (GOP) accounts for the beneficial changes in food preferences, sweet taste function, and eating behavior after RYGB, rather than the impact of these peptides, since they are not a standard therapeutic option for patients with obesity and/or (pre-) diabetes.

In this case, please consider making the purpose of the study clearer in the Introduction section (e.g., the contributing factors to the beneficial shifts in taste and eating behavior following RYGB remain elusive).

1. Table 4 is not mentioned throughout the whole manuscript. It is likely that the last “Table 3” in the last subsection of the Results section is a typo and should be changed to Table 4.

2. The first p-value in Table 1 indicates a statistically significant difference in sex distribution among groups (RYGB has more females, obviously).

As a reference of the peak postprandial concentrations of tripeptide at 1-month post-surgery, does this difference in sex influence the levels of these peptides in patients undergoing RYGB?

Are the designated dosages of these peptides applicable for the other two groups with a different sex distribution? Please consider providing explanations on this point.

Dear author,
It is a pleasure to review an article of a such an interesting topic, and I am very glad that all my previous comments and questions have been properly addressed. Thank you.