For today’s edition of Dear Mark, I’m answering a pair of questions. First, a new study comes out and claims that branched chain amino acids increase the risk of insulin resistance and, eventually, diabetes. The study is legit, but the test subjects were mice. Is the research relevant to humans? Then I explain just why the interesting weightlifting article with all the exclamation points from last week’s Weekend Link Love got me thinking.
I’m a little worried. I’ve been taking BCAAs for the past few months, mainly to reduce hunger and increase muscle retention during fasts. then this study hits claiming that low BCAA diets improve metabolic health. Should I stop?
First off, that was a mouse study .
The authors of the mouse study try to make their results relevant to humans, citing a human study  in which elevated BCAAs in serum correlated well with insulin resistance. Other research  finds links between elevated serum BCAAs and obesity and, at least in whites and Hispanics (but not blacks), elevated BCAAs and diabetes .
It turns out that serum amino acids are in constant flux, and many medical issues can determine which amino acids show up in the serum . Serum levels of BCAAs may not even necessarily reflect dietary intake. In obese women , for example, taking BCAA-rich whey had no effect on serum BCAAs. Assuming high BCAAs in serum cause and don’t just correlate with obesity and insulin resistance, it’s unclear whether eating more BCAAs necessarily elevates serum BCAA.
What happens in humans (you are human, right?) who eat more BCAAs? Good things:
It activates the enzymes  necessary for muscle protein synthesis post workout.
It reduces muscle damage  after training.
It stimulates muscle anabolism in older women , with or without training.
As for the metabolic issues raised in the mouse study, we have some relevant observational studies on dietary BCAAs in humans:
In Japanese adults, high intakes of BCAAs are associated with  lower rates of diabetes.
In middle-aged Eastern and Western adults, high BCAA intakes predict  lower rates of obesity.
In Chinese adults, a higher ratio of dietary BCAA predicts  lower rates of obesity, high blood sugar, and inflammation.
I don’t actually see a need for branched chain amino acid supplements in most people. They have very specific uses—staving off muscle loss and increasing muscle gain during fasts, especially when taken before training—but the majority of us get plenty of BCAAs in food form. Foods like whey  protein, eggs, and most meat  and fish  are fantastic sources of BCAAs, and the observational studies finding beneficial links with high dietary BCAA are talking about those types of sources, not BCAA supplements.
To sum up, you don’t have to worry. You’re using BCAAs for the right reasons, in the right manner.
I’m with you, David. A joke of a post. Not sure why this drivel would get Mark “thinking.”
At this point, I should probably reiterate that “links are not full-throated endorsements.” I link to articles that contain interesting viewpoints. Sometimes I disagree with the links. Sometimes I agree with some of the content and disagree with the rest.
Here’s what I liked about the article:
The idea of gyms as an unnatural, artificial environment.
I don’t necessarily agree with this stance. I do most of my lifting in a gym, because it works and it’s convenient, but I also recognize that I’m doing something rather artificial. If I could I’d probably train outdoors every time. There are real benefits  to that. As it stands, the majority of my play—Ultimate Frisbee, paddle boarding, hiking, slacklining, and any other non-gym physical activity—takes place outdoors in as close to a natural setting as possible.
“If you can’t shoulder it, you shouldn’t be working with it!”
This appeals to me. The ability to safely move a weight from the ground to your shoulder is a strong and probably reliable signal that you can safely manipulate it in other ways—squatting, pressing, pulling. It may not optimize your strength gains, but it’s a good heuristic for keeping injuries at bay while getting you strong “enough.”
The emphasis on loaded carrying.
From farmer’s walks to heavy rucking to carrying groceries to packing out the elk you just shot 4 miles from your car, we’re meant to lift things up and carry them for distance. It builds toughness, durability, places a unique 20-30 reps of squats while holding a heavy weight? Useful and beneficial, but evolutionarily novel. And a little odd; just imagine how a Hadza bushman would react to a CrossFit class.
The warning against letting your ego guide your training.
One of my worst training injuries happen years ago when I strained my shoulder going for a PR on the bench press. I didn’t have any real “reason” to train so hard. I didn’t “need” the big bench. It’s important to be strong, and given the choice I’d prefer to be stronger than not, but that mentality, taken to the extreme in service of the ego, will almost certainly lead to injury.
The exclamation points.
It’s refreshing to see a guy go through an entire blog post at the top of his lungs.
Is it a flawed blog post? Absolutely. Does it contain useful concepts? Yes. The cool thing is that you can take the stuff that resonated and discard the rest.
Thanks for reading and asking, everyone. Take care and be sure to comment down below!