This study is based on analysis of a unique dataset following individuals over time, measuring both fat and determining presence of pathogens. Such datasets are few. Overall, I find the paper of high quality and interest, though there are some unclear sections in the analysis and presentation of results.

Comments
I would try to avoid overstatements and too broad generalizations about effects. I would tone down in title. From figure 3 (that is a bit difficult to understand alone) – I think a better title just excluding “are comparable to that of reproduction”. Or you could change “are comparable” to “compared to”. Further, e.g. L80, you do not show effects on population dynamics. L90. Not sure we learn about the trade-offs or consequences for population dynamics.

L155. You fix a detection rate of 0.85. I cannot see how this should solve the issue of variable duration between sampling events between summer and winter? Also, with 9 months for summer – you should probably denote it differently?

L189. I suggest you describe the functions – and their basis a little better. I struggled to follow how this was done. Did you use model output to calculate table 2?

L159. Area as a covariate - add “categorical”? Did you test for interactions with the other variables? Looking at the figures, could some effects be driven by differences between areas, or be different between areas? E.g. Upper Shoshone in fig. 2c?
I assume individual ID was a random term? I didn’t see this stated.

L208-211. This was not clear. I read it as pathogen was acquired between two points in time, then by definition it would be present at the end of season? Actually, this whole paragraph (L208-219) make me wonder about wording. “End of season” – do you mean “end of year”?

Typos/minor
L18. “costs of rearing”. Maybe add in terms of fat reserves (costs may be more).
L20-21. A bit strange to state “may result in tradeoffs between reproduction and survival”. May affect the tradeoffs. But I suggest to delete the end part of sentence.
L76-93. Try to condense the text.
L127-128. Rather, «it is possible our metrics of infection underestimated the true infection load”
L170. “.” Lacking after [37].
L178. Strange “global models for over-summer models”. Remove one “model”.
L226. spell out ppt – no need to use acronym.
L230. “over summer overwinter”?
L244. Not sure the sudden link to “dynamic energy budget theory” is useful – delete?
L262. I find it misleading to link with something similar to a “multiplier effect” – I recommend to delete.
L262. Not directly – indirectly through reproduction and survival.
L264. “Cascading” is usually used for effects going between trophic levels. Recommend to find another term or just remove.
Conclusions is way too long. Delete from L307.