Why Guessing Your Metabolism Doesn’t Work

If you’ve ever tracked calories, tried a new diet, or relied on a wearable or fitness app to tell you how many calories you burn, you’ve probably run into the same frustration: why don’t the numbers add up?

Maybe you’re eating what your app says is the “right” amount, but the scale won’t budge. Or maybe you’re training hard, tracking your workout and being consistent, feeling like you’re eating healthy, but still your energy’s off. The trouble is that most of the information we rely to manage our health is based on the law of averages. And your body doesn’t run on averages.

At BioFit Philly, we specialize in taking the guesswork out of fitness with Resting Metabolic Rate (RMR) testing and VO2max testing — simple, science-backed ways to understand exactly how your body uses energy.  

Let’s start with the RMR test.

relaxing during an RMR Test

What Your RMR Really Tells You

Your Resting Metabolic Rate (RMR)* is the number of calories your body burns just keeping you alive — the beating of your heart, brain functioning, breathing. It’s the baseline energy your body needs every single day, before you add in workouts, walking, or even fidgeting.

The problem? Most people rely on online calculators or smartwatch estimates, which can be off by 10–30%. That’s hundreds of calories a day — enough to completely throw off your goals.

Instead of guessing, RMR testing measures your body’s actual oxygen use and carbon dioxide output to calculate energy expenditure with precision. It’s not an estimate; it’s your real metabolic fingerprint.

* When you’re reading about metabolic testing, RMR and BMR are often used interchangeably.  BMR is your Basal Metabolic Rate, RMR is your Resting Metabolic Rate. What’s the difference? BMR is typically measured under strict laboratory conditions - putting it out of reach for the general public.

Why Guessing Keeps You Stuck

When you don’t know your true RMR, it’s like trying to plan a road trip when you don’t know the size of your gas tank and might suspect a broken fuel gauge.  You can make your best guess, but it’s still a guess.

People relying on guesses too often fall into one of the following traps:

• Eating too little: Your body adapts by slowing down metabolism. You burn fewer calories, feel tired, and hit a plateau.

• Eating too much: Even healthy foods can add up quickly if your energy needs are lower than you think.

• Training without recovery: If your fuel intake doesn’t match your actual needs, performance and recovery suffer

Knowing your RMR gives you a roadmap  — how much fuel your body truly needs to perform, recover, and change.

Real Data = Real Results

Once you know your RMR, your nutrition and training can be tailored to fit your own unique physiology — not someone else’s. Some people discover they’ve been undereating for years, while others learn they can eat more and still make progress. They just didn’t have their metrics!

Your metabolism isn’t just “fast” or “slow” — it’s specific. When you know your numbers, you stop fighting your body and start working with it

In Practice: How We Use It at BioFit Philly

At BioFit Philly, RMR testing is one of the foundational tools we use to help you design smarter fitness plans. Measure, interpret, and then turn the data into practical action.

You’ll leave your session knowing:

• Your calorie needs for maintenance, fat loss, or performance

• How to apply real numbers to your nutrition and workouts

• And how to stop second-guessing your calories in/calories out

It’s one of the most empowering tests you can take — because once you know your RMR, you can finally make your effort count.

Stop Guessing. Start Measuring.

If you’ve been doing everything “right” and still not seeing the results you expect, it’s time you get yourself some real data.
Schedule your Resting Metabolic Rate (RMR) test at BioFit Philly and see how powerful it feels to train with precision.

How Can I Improve My VO2max?

Improving VO2max, or the maximum amount of oxygen your body can use during exercise, is crucial for enhancing cardiovascular fitness and overall endurance. There are several effective exercise strategies to increase your VO2max, many of which focus on aerobic conditioning and pushing your body’s limits during intense exercise.

High Intensity Interval Exercise (HIIT)

HIIT involves alternating between short bursts of very intense activity and periods of rest or low-intensity exercise. For instance, sprinting for 30 seconds followed by one to two minutes of walking or resting, repeated for several rounds, can significantly increase VO2max. HIIT pushes the cardio-respiratory system to adapt to higher oxygen demands, leading to improved aerobic capacity.

Steady-State Cardio at High(ish) Intensity

Sustained aerobic exercises, such as running, cycling , or swimming at a high but manageable pace can help boost VO2max. Performing these workouts at about 70-85% of your maximum heart rate encourages your body to adapt by improving oxygen utilization and efficiency.

Fartlek Training

Yeah yeah. The term Fartlek training is often used synonymously with HIIT, and they are very similar; however, HIIT is generally predetermined lengths of sets and ratios of work to rest, while Fartlek training is more random and spontaneous. The unpredictability can be an excellent companion to HIIT, and when needed, help break through some plateaus.

Tempo Runs or Threshold Training

This strategy involves running or cycling at a "comfortably hard” pace for extended periods, just below your anaerobic threshold. These sessions train the body to become more efficient at using oxygen over long duration, gradually improving VO2max.

Longer Endurance Workouts (steady state)

Engaging in longer duration exercise, such as cycling or hogging for 60+ minutes at moderate intensity, builds aerobic endurance and improves the ability of the heart and lungs to deliver oxygen efficiently.

Incorporating a mix of these strategies into your workout routine will challenge your cardiovascular system, push your aerobic limits, and ultimately improve your VO2max. regularly increasing the intensity and variety of your aerobic exercises will lead to measurable gains in fitness and overall health.

Get measured and improve!

The Role of VO2max in Longevity

VO2max, or maximal oxygen uptake, is a key indicator of cardiovascular fitness, representing the maximum amount of oxygen the body can use during intense exercise. For individuals aiming to increase their longevity, VO2max plays a crucial role in assessing and improving overall health and physical performance. If you’ve read the best-seller Outlive by Peter Attia, you’re probably at least familiar with the role of VO2max in human longevity.

One of the primary benefits of a higher VO2max is its strong correlation with cardiovascular health. research consistently shows that individuals with higher VO2max levels have a lower risk of heart disease, stroke, and metabolic conditions like diabetes and cancer. By improving the heart and lungs ability to deliver oxygen to muscles, it allows for more efficient physical function and resilitence during everyday activities.

Moreover, a higher VO2max is associated with improved motochondrial function and metabolic efficiency, which are vital for slowing the aging process. Those with better aerobic fitness tend to experience fewer declines in physical capacity as they age, maintaining independence and quality if life for longer.

Incorporating activiteis like running, cycling, or high-intensity interval training (HIIT) into your fitness routine can significantly improve VO@max. As it increases, it not only boosts endurance and stamina but also enhances longevity by supporting cardiovascular health, reducing disease risk, and promoting healthy aging.

In summary, improving VO2max is a key strategy for those aiming to extend their lifespan and maintain vitality as they age. It serves as both a marker of current health and at ool for ensuring long-term well-being.

Why Training With Test Results is Better than Training With Estimations

I know, it sounds obvious. But with the prevalence of wearable devices and the lack of accessibility to legit testing, it’s understandable that most people would default to using a basic estimation; I’m going to tell you why there’s a better way.

Using heart rates derived from a VO2max test that actually measures your oxygen uptake and CO2 output is far more accurate and effective for improving VO2max than relying on estimated heart rates. Here’s why:

Personalized Training Zones

A VO2max test provides precise data on your body’s unique physiological responses, including exact heart rate zones that correspond to different levels of exertion (aerobic and anaerobic thresholds.) Training within these personalized zones ensures that you’re pushing your body to the optimal intensity for improving VO2max, unlike estimates that are based on general formulas (like 220 minus age) which may not reflect your actual capacity.

More Effective Workouts

Heart rates from a VO2max test ensure you’re working hard enough to challenge your cardiovascular system without over-training. This targeted approach makes training more efficient, leading to faster improvements in VO2max. By contrast, estimated heart rates might result in working below or above your ideal intensity, slowing progressor increasing injury risk.

Real-Time Feedback

With specific heart rate data from a VO2max test, you can monitor your performance during training sessions in real-time. This allows you to adjust your effort immediately to stay withing the desired zone, ensuring you’re consistently working at the correct intensity to boost oxygen utilization and aerobic capacity.

Individual Variability

VO2max test date accounts for individual differences like fitness level, heart rate variability, and genetics, which standard estimations overlook or are simply unable to account for. Two people of the same age can have vastly different heart rates and thresholds, meaning an estimation could be too hgihg or low for one of them. Using test-derived heart rates eliminates this issue.

*I have no interest in getting into a flame-war over the accuracy of wearable devices; I will just say this: VO2max is the maximum volume of oxygen (respiration) that you can consume,expressed in milliliters of oxygen consumed, per kilogram that you weigh, per minute that you exercise. The device on your wrist isn’t measuring the volume of any air, so it’s a different type of aggregated estimation.