FWIW, I haven't seen any real convincing info, but those most consistent answer I've seen is that metabolic changes can start to happen in 10-14 days. The big variable left out is the weight/health/fitness level of the person. I'm guessing that an obese person who hasn't gotten off the couch in 3 years has more leeway than someone who's already pretty active with a reasonably healthy body fat %.

TIFWIW though...

Tagging for later.

So I'll preface this with an acknowledgement that any true specifics will come down to 'well, it depends', but I still think it's a question worth answering.

Given that nutrient intake timing is largely irrelevant, over what period of time does it actually start to matter?

I'm of the opinion that the pendulum has potentially swung too far in the other direction on this topic and I'm guilty of it myself. I think nutrient timing MAY matter, but under most real world conditions where people are eating multiple mixed meals and getting multiple protein doses in, the differences between these real world scenarios are probably somewhere between minimal and negligible assuming adequate total nutrition is in place.

I certainly haven't looked at all the research but I think there's a substantial amount of studies looking only at acute effects and often times comparing inadequate total intake. (Aragon/Schoenfeld meta is a great one).

So as it pertains to your post, my gigantic assumption is that it does matter. It just doesn't matter very much in comparison to total intake, and assuming you're eating something relatively normal, like 2 to 5 meals per day, I'd think the differences in intra-day timing are even less important within that framework.

Whereas comparing say, 1 meal to 15 meals would probably show a larger difference, or eating triple the calories/macros every 3 days and fasting in between would probably show an even bigger difference. And I'm basing this on assumption entirely, take that into consideration. Obviously these previously mentioned scenarios are pushing levels of stupidity that only take place in internet discussion but hopefully it makes sense.

I've got my final weigh-in for a weight loss competition next week Thursday, and I plan to cut weight for it (I know how to do so relatively safely and am comfortable with the toll it'll take on my body in terms of reduced performance in the gym, and general feeling of crappiness compounded by lack of ice cream. I'm also going on vacation the week after, to an all-inclusive in Mexico. My diet at that point will be, quite literally, the exact opposite of what it will be while I'm cutting for weigh-in.

So I know (or at least, I assume) that this two week stretch isn't going to have lasting long term implications on my diet and body recomposition efforts, but at what point does it start to matter? I suspect if I were to cut hard for three months I'd lose a decent amount of LBM, and likewise if I bulked on tasty tasty frozen beverages for three months after that I'd gain a lot of fat.

I don't think you are going to do any considerable damage in 2 weeks, assuming you're not doing anything totally idiotic.

So the question, and again acknowledging that a precise answer would vary at least a little from person to person, is over what timeframe nutrient timing does start to matter? After what period of time on a cut does LBM retention really start to tank?

Thank you in advance.

Regarding the LBM question, I haven't seen any research on this that I recall. The worst case scenario that I can see happening is that you atrophy a bit and it takes you an extra two weeks in the gym to bounce back.

I do agree with Rock, that leanness will be a very big factor in this. As an indirect example, I went more aggressive on my diet the first two weeks of this cut because I'm fatter and can afford to go a bit faster. I wouldn't make that same decision (proportionately) near the end of my cut because in theory it would be harder to spare lean mass.


So those are my random grey area comments that probably don't answer your questions.