Knowing, and Dialing In, Your Basal Metabolic Rate

What is BMR?

What you eat is venturing dangerously close to who you vote for or where you pray. In other words, diet has a way of moving from science-based practices to something more akin to a belief system. So this primer is not designed to say what you should do, but provide a general template to work from.

Let’s start at the most basic level. Your body has a basal metabolic rate (BMR), which varies from person to person. There are lab-based ways to get exact with BMR, but a general online calculator will do the trick for most people. BMR is higher for men who have higher body-mass indexes (BMI), and lower for women with lower BMIs. For example, the BMR for a 5’2”, 25-year-old woman weighing 110 pounds is 1200 calories per day, assuming she is sedentary. Meanwhile, a 6’5”, 250-pound man of the same age has a BMR of 2070 calories per day.

Your BMR is the baseline number of calories it takes to maintain bodily functions without going into an energy deficit. Going below that number is called negative energy availability, which is good if you are trying to lose weight, but is also connected to running-related injuries and overtraining due to lack of fuel to repair stressed physiological systems.

Knowing your BMR

Add exercise to the mix and things get a lot trickier. It varies a lot, so we won’t break it down here, but running one mile can burn up to 100 calories, with variation for age, gender, weight and running experience. In other words, if you run lots, you need to eat lots.

Failing to fuel enough can work in the short-term for some people that need to lose weight. But long-term negative-energy availability while training can lead to overuse injuries, reduced libido and countless other maladies that make running (and life) far less enjoyable. So the stakes are high when it comes to running-related fueling.

At the threshold level, make sure you are getting enough calories for your goals. That is step number 1—avoid thinking that less is more and skinny is fast. Instead, reframe it in this way: “strong is fast.” To be strong, you must fuel.

PRO TIP

Vitamins and Minerals that Matter
If you want to have fun on a slow news day, Google, “Should I take vitamins?” and check out some of the passionate answers. Vitamins are shockingly controversial, so we won’t debate that here. Instead, here is a brief primer on the supplements that you’ll see many runners taking to maintain their health.

1. Vitamin D. Vitamin D is essential for bone health and is connected to numerous other health outcomes, so, unless you are getting lots of sun on exposed skin, it may be good to have a supplement between 1000 and 5000 IU per day, at the direction of a doctor.

2. Iron. Iron is essential for healthy red-blood-cell formation, and iron deficiencies can make runners feel like trail zombies. Running breaks down iron through foot-strike hemolysis, where blood cells themselves are damaged each footfall. Iron deficiency—even when it doesn’t amount to anemia that might be flagged by a blood test—can hurt performance. Most top female runners take an iron supplement between 18 mg and 65 mg. Most male runners should get a blood test before taking an iron supplement.

3. Multi-vitamin. While a multi-vitamin may be unnecessary if you have all of your diet boxes checked, it is sometimes difficult to get everything you need if you are on-the-go. Consider a multi-vitamin if you are worried.