Choose two. You’re probably not going to get all three in the world of fitness.
If you’ve ever been in a fitness or nutrition debate, you’ve likely heard people throw around numbers with a confidence that borders on religious zeal. “I burned precisely 457 calories in that workout,” “I’ve walked 10,000 steps a day for a month,” or “This meal is allows me to reach my maintenance exactly.” These statements sound impressive, but they bring up a crucial question: what matters more: precision, accuracy, or consistency?
The typical metaphor for precision and accuracy used is to ask the reader to visualize an archer shooting arrows at a target. If the archer shoots a hundred arrows and they all land in a specific spot, they are a precise shooter. Likewise, if the archer shoots a hundred arrows and they are all clustered near the bullseye, the archer is accurate (but not necessarily precise).
I’d like to add a third phenomenon to this metaphor: consistency. If an archer shoots 100 arrows a day, are the arrows near the same spots day-by-day? If so, that archer is a consistent shot. This three-way distinction becomes crucial when we start applying these concepts to our fitness journey.
A lot of young kids can very definitively tell you the number of jelly beans in a jar. Ask one and you’ll get an answer of something like “ten million nine hundred and seventy one”. And that’s totally wrong… but it’s precise! Precision is all about giving you an exact number with lots of significant figures. It’s the difference between saying “I ran about 3 miles” and “I ran exactly 3.27 miles according to my GPS watch.”
Within the health and fitness world, bioelectrical impedance scales are a great example of precision. You’ve probably been on one of these before. Many smart scales tell you your supposed body composition by running a tiny electrical current through you and running a calculation to tell you what your exact body fat percentage is. They are extremely precise. You might step on one and it’ll tell you your body fat is exactly 18.56%, and your left arm weights 20.01lb. Is that reflective of your actual body fat and left arm weight? Who knows!! But it’s certainly precise!
This kind of precision can be seductive… after all, exact numbers feel scientific and trustworthy. But if this precision isn’t consistent or accurate, it’s just precise rubbish.
Accuracy
If you know anyone with a green thumb, you’ll know that they have the uncanny ability to keep their plants alive and happy. A lot of this boils down to watering them the right amount. Some gardeners are meticulous with the exact amount of water they give their plants, and the exact days they are watering said plants. But most gardeners are eyeballing it. This is, in effect, accuracy. They may not know exactly how much they are watering their plants, but they are keeping them alive and happy, so it must be an accurate amount.
Within fitness and health, a lot of measurements are accurate and imprecise. A great example is a typical “serving size.” Usually this is given as about the size of a palm.1 That is an accurate measurement. It’s in the right direction and it gets you where you need to go.
This “good enough” approach often yields better results than obsessing over precise measurements, especially for beginners. After all, the most accurate measurement is the one that helps you achieve your goals, even if it’s not the most precise.
Consistency
When I go bowling, something strange happens. Around half of the time, I get nonstop strikes and spares. And the other half of the time? All gutters. The reasoning behind this (besides having no idea what I’m doing when it comes to bowling), is that I am inconsistent.
Consistency can have a lot of definitions, especially when it comes to the world of fitness. In terms of this article, let’s call consistency the ability to replicate results within a reasonable margin of error over time. It’s not about being perfect, it’s about being reliable (or: consistent).
When it comes to weight loss, for instance, consistency can be measured in things like your pants size. It’s probably going to change as you lose or gain weight, but very slowly, to the effect of basically being a constant. Your pants size is not going to vary day to day — it is consistent measurement.
On the contrary, your water weight (ie, the amount of water you’re carrying), is likely to be a very inconsistent measurement. Pretend you’re the mystical type of intuitive eater who can vary their diet each and every day, and still stay at around maintenance. If you were to look at your daily weight, it’s actually probably going to change a fair amount each day. Yesterday maybe you had 3500mg of salt, and today you had next to no salt. The amount of water you’re carrying is going to vary a lot. Thus, water weight is an inconsistent measurement in terms of weight.
Calorie counts for ingredients are precise and consistent
But not accurate!
Nearly all calorie counts you find in foods are derived from an early 1900s paper. You might think that makes them the gold standard. But in reality, calorie counts are consistently off of these values. Errors are constantly compounded, and the result is that calorie counts are really more of a vibe than an accurate measurement. But they are consistent and precise. That Starbucks latte I bought today may or may not actually be its stated 190 calories, but whatever its true value, it’s probably consistent day to day.
Since these counts are also precise (190 calories!), they still serve a real purpose, and can be used in good calorie tracking. A calorie app I like a lot called MacroFactor (from the folks who publish Stronger by Science), has a great article on consistency vs. accuracy in calorie counting that I highly recommend reading (also, this article is not sponsored, and please note that while MacroFactor rocks, it’s not free).
So? What do we do with this information?
How you utilize this triad of terms is up to you and your goals. Personally, I prioritize accuracy and consistency. Precision in the world of weight loss rarely matters to my personal goals, and the same is likely true for nearly everyone (except maybe in the case of calorie counting, where as discussed previously precision and consistency matter more). In this respect, that means that if my or a client are visually losing weight and feeling better, it doesn’t matter what the precise body fat number is.
There are of course exceptions. If you or your client is training for a bodybuilding competition, it’s likely an exact weight is trying to be achieved. In that case, you likely are targeting accuracy and precision, but not consistency (we want a weight of precisely X on the tournament day using the tournaments mode of weighing, but the day after doesn’t matter. And it also doesn’t really matter if that weight can’t be replicated on other scales).
There are of course times when precision, accuracy, and consistency are required (such is the case when administrating medication to a patient), but I would argue that when all three of these things are present, we’ve likely left the world of fitness and have moved into the world of medicine.
In the end, the key to successful fitness tracking isn’t about achieving perfect precision, accuracy, and consistency in everything you measure. It’s about understanding which of these qualities matters most for your specific goals and circumstances. Sometimes, a rough but consistent measurement will serve you better than a precise but inconsistent one. Other times, accuracy might be crucial while precision is less important.
By understanding these distinctions, you can focus your energy on the measurements that truly matter for your progress, rather than getting lost in the weeds of numbers that might be precise but ultimately unhelpful. Remember: the best measurement system is the one that helps you achieve your goals, whether that’s through precision, accuracy, consistency, or some combination of the three.
