Nutrient timing, and why sex matters in nutrition research

If you’ve been involved in strength training for any length of time, you’ve probably heard of the “anabolic window.” This is the period of time, typically around an hour, after a workout that your body is primed for protein synthesis (in super layman’s terms, the process where your body takes ingested dietary protein and uses it to rebuild your muscles). You’ve probably heard arguments both for and against the existence of this window. Recently, I’d say the trend has been to disregard the idea of an anabolic window altogether. Most of the science-y instagram accounts will proclaim that research shows this effect has been oversold, and that the anabolic window is really more like 24 whole HOURS after a workout. The 60-minute window is now disregarded as “broscience.”

And it’s all true, if you’re male. For female athletes, that old piece of “broscience” just so happens to be (almost) correct. In fact, according to Dr. Stacy Sims, an exercise physiologist and nutrition scientist specializing in sex differences in these fields, we should be consuming protein within just 30 minutes of a hard workout. So how does a key piece of info like that get missed?

Who participates in research studies?

Most exercise science and nutrition science research is done on college-aged males, both trained and untrained. Why? Because it’s easier. College students are more likely to take part in research studies if it’s required by their school (I was required to be a participant in several psychological studies as an undergrad as part of my degree). In addition, male participants are easier to work with than female participants because they lack a menstrual cycle and all the hormonal fluctuations that come with it. 

A woman on Day 1 of her cycle is not the same as a woman on day 18 of her cycle. That big hormone fluctuation can mean major issues with the data collected during a study. It’s a variable that needs to be accounted for, but is often just thrown out, along with female study participants. The data collected about males is then extrapolated to everyone by the media reporting on those studies, and we end up here, giving female athletes suboptimal advice on how to fuel themselves.

Protein timing for female athletes

So let’s get back to that protein timing advice. Why do female athletes have an abbreviated window for maximizing protein synthesis? There are a couple steps, but they all lead to progesterone, the hormone that dominates the second half of our menstrual cycle. 

Progesterone is catabolic in nature, meaning it encourages the breakdown of molecules and tissues (vs. anabolic, which would encourage building or maintaining molecules or tissues). The second half of the menstrual cycle, called the luteal phase, is driven by a dramatic rise in progesterone released after ovulation. This “high hormone” phase brings with it a bunch of physiological changes in the body that can be frustrating for women who lift.

And if you’re reading this and thinking, “I’m good, I’m on the pill,” not so fast. Your pill definitely includes a synthetic progestin, which means you’re likely experiencing these affects all the time.

While this can seem kind of… upsetting at first read, it’s ultimately empowering to understand this aspect of our physiology. Yes, we have some added challenges, but KNOWING that we need to take some steps to help our bodies out during this time means we can now get out ahead of it.

And it can be as simple as taking in some protein right after you finish training hard. About 20 grams of protein, preferably with some additional carbohydrates too!

Your menstrual cycle is not an excuse NOT to train. It’s a reason to ADD some targeted nutrition to your day.

I’m saying ADD on purpose here too. We burn an additional 100-200 calories per day during the luteal phase. Ever wondered why your cravings seems to get out of control around this time? It’s because you’re actually really hungry, and your body needs food! So add that quick protein shake in right after a workout. Throw a banana in there too and replenish the glycogen you just used to train. Now you’re on track to recover more quickly and get back to the weightroom (or the trail or the field). 

I’ve plugged her book before and I’ll do it again now! ROAR by Dr Stacy Sims is full of vital information for female athletes at all stages of life and I cannot recommend it enough. I’ll continue to recap some of her main points here and in practice with my clients. I have felt the differences in my own training and my clients have too!

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