That time I did indirect calorimetry

*trigger warning: I will be discussing calories and calorie needs here. If that’s triggering for you, skip this post!

If you’re not familiar, indirect calorimetry is a tool used to assess energy expenditure and fuel utilization in the body by measuring oxygen consumption and carbon dioxide production. Basically, you breath into a tube for about 20 minutes, and a machine does a bunch of high level calculations to determine your resting energy expenditure (REE), and therefore the minimum number of calories you’d need to consume in a day at rest to meet your body’s needs. The information I received also included the minimum number of calories I needed for general every day activity (like walking to the grocery store).

Photo by Myriam Zilles on Unsplash

Before I share my results, it’s important to chat about why I’m sharing this. It’s really common, especially for women and female athletes, to underestimate energy needs. Especially when bombarded with messages that we must at most consume only a 1,200, 1,500 or even 2,000 calorie diet. The reality here is that a 1,200 calorie diet is barely enough for a toddler, and for an adult it’s nothing short of starvation (and I will die on this hill). It’s safe to say that most of the women I’ve worked with over the years (hundreds of them!) have needed to be consuming 2,000 calories or more per day to meet their body’s needs. I of course did not do indirect calorimetry on them, but we dietitians do have other calculations that are useful. This can be a hard pill to swallow after years, and sometimes decades, of believing that less is more.

Which is why I often share my indirect calorimetry results with clients as evidence to the contrary, and as a helpful discussion starter. To be clear, it’s never used as a comparison, I don’t talk numbers with every client, and I’m comfortable with this kind of self disclosure.

How many calories I needed in a day
I had my test done in an endocrinologist office several years ago (2013 or 2014, I think!), and suspect my results may be slightly different now as I’m not running marathons. But, here are what the results showed:

At rest with general daily activity factored in, I needed between 2,200 and 2,400 calories per day. Again, that does not include any running. At the time, I was probably running maybe 50 miles per week, upwards of 60 if I was marathon training (which I almost always was), and would estimate my needs upwards of 3,000 calories or more per day. To a lot of female athletes, this is a scary sounding number. I would argue that it’s actually just a realistic number, and many female athletes likely need at least this much when it comes to calories, especially those in endurance sports.

Takeaways
The majority of female athletes I work with are likely falling short of meeting their energy needs when we start working together (unintentionally or intentionally). Sometimes talking numbers isn’t appropriate and can be triggering, and sometimes it can be incredibly eye-opening. It’s also important to note:

• Energy needed at rest for endurance athletes is also elevated. Meaning, rest days, off season, injuries still require adequate nutrition and this can also be greatly underestimated. Restricting during this time is also of course not the answer!

• It takes work to meet energy needs when they are on the higher side. That means three meals and often at least three snacks per day, that all include energy dense foods. Planning is key! Fat, which has more calories per gram than protein or carbohydrates, can also be very helpful here

• This of course is an N of 1 (me!), but the more examples of female athletes eating more and enough, the better. Remember during the Olympics (maybe 2016 or 2012) when the media made a huge deal about Michael Phelps consuming 6,000-8,000 calories per day? We need more of that but for women.

I hope this was helpful!

For more information on working with me, please visit my website.