Recently, I read an article titled ‘Why women should not run’. Initially, I found the article amusing. But then I found it really started rubbing me the wrong way, and I decided to answer. What is in the article? Well, essentially a long list of reasons why endurance workouts at the gym are useless, and don’t yield benefits. And then this is followed by a long list of articles supporting the claims.
What is the main idea? The argument is this: too much endurance will lower certain thyroid hormones (T3, T4, TSH, … ) which in turn makes it impossible to lose weight, regardless of physical activity. And that’s where the wheels start to fall off.
Indeed, it is well established that hypothyroidism is often associated with weight gain. However, to reach these levels of low thyroid hormones, you need to be in a very heavy training phase, typically seen at the elite level, where being lean is not an issue (although there are issues associated with being too lean, among women).
This is where things get interesting. The first article cited is “Resting thyroid and leptin hormone changes in women following intense, prolonged exercise training” (Baylor LS, Hackney AC. Eur J Appl Physiol. 2003 Jan;88(4-5):480-4.) The group considered in this study consists of females participating in running, rowing, and weight lifting. Yet, the article singles out runners. Interesting. The article also explains that post-heavy training, the thyroid hormone levels go back to normal. But, still, the interesting part is that it includes women who lift weight, and row (which is far closer to weight lifting, crossfit, etc, than to running), and these women show the same drops in thyroid hormones. I look at the entirely literature list actually. Many articles are not women specific, so they are not appropriate to support the article’s claims. Some are rats/mice models. Good try though. Others are well known biochemistry results linking thyroid hormones and thermogenesis regulation. One actually discusses thyroid hormone levels and sleep-deprived young men (I’m still trying to get the link there…) But what thing is missing…
So, the author doesn’t like running, I get it. He wants people to do CrossFit types of training? Fine with me. They are actually pretty decent, provided they come with adequate warm-up, which is something lacking, at least in the sessions I have done and witnessed. The issue I have is when he claims that one training is better than another. Or that his approach is the ‘best in the business’. So, what is missing is well if crossfit, HIIT, etc. is superior (based on the single thyroid hormone levels criterion, which is very debatable…) I guess those who engaged in these activities don’t see drops. Wrong! The author conveniently ignored the work by Pakarinen et al. (88, 91, 93 — pubmed is your friend) showing that the same (reversible) changes occur in weight lifters and other such activities. The article takes a whole bunch of other shortcuts which are more or less entrenched in selective and confirmation bias. Disingenuous at best.
What is the bottom line? All physical activities are good. What is not good though is to present your system or approach as the best there is. Something triathletes used to be guilty of (and still are). And something we see over and over again on the CrossFit fora. All physical activity coupled with appropriate nutrition will help you lose weight, provided of course you don’t overestimate calorie expenditure, and underestimate calorie intake, you balance proteins, carbs, fats appropriately etc. But if you want to be a better runner, running will do the trick much better than CrossFit (see my previous entries on weight training, and the Q&A). If you want to be kind of good at everything including lifting, jumping, being explosive, etc. then CrossFit will do that much better than running.
So, find something you like, move, eat well and be happy.