Ever wondered how accurate your calorie target really is?
Whether it’s from MyFitnessPal, a smartwatch, or a coach’s calculator, the truth is, your calories are never exact. And that’s not a bad thing.
At The Lab Liverpool, we use evidence-based methods to estimate how much energy you need each day. But that number is just a starting point. The real work, and real results, come from adjusting based on feedback, performance, and how you actually feel.
Where Do Calorie Estimates Come From?
Every calorie target starts with an estimate of your Total Daily Energy Expenditure (TDEE), the total energy your body burns each day.
That includes:
• Basal/Resting Metabolic Rate (BMR/RMR): the energy needed to stay alive at rest
• Physical Activity: training, daily movement, and steps
• Food Thermogenesis: the small energy cost of digesting food
To estimate this, we use predictive equations. Over time, several have been developed, each with strengths and limitations.
A Quick Look at the Most Common Calorie Equations
1. Harris-Benedict (1919)
One of the oldest and most widely known formulas, created over a century ago. It calculates resting metabolism from your height, weight, age, and sex.
However, because it was based on early 20th-century populations with very different lifestyles and body compositions, modern studies consistently find it tends to overestimate energy needs, often by around 5-15%.
In one comparative study, fewer than half of Harris–Benedict predictions matched measured metabolic rates within a 10% margin (Liu et al., Medicine, 2024).
2. Mifflin-St Jeor (1990)
Developed later using a larger, more modern sample, this is now one of the most accurate and practical formulas for estimating RMR in the general population.
In research comparing different equations, Mifflin–St Jeor produced the closest match to measured values in both non-obese and obese adults (Frankenfield et al., Journal of the American Dietetic Association, 2005).
Still, even this equation can be off by up to 10–20%, depending on muscle mass, genetics, and daily activity.
3. Revised and Other Modern Formulas
Newer versions, such as the Revised Harris–Benedict (Roza & Shizgal, 1984) and updated 2023 models, have attempted to correct earlier bias. They perform slightly better in some groups but still fall within a similar error range. Other options, like the Henry (2005) or Schofield equations, are more common in clinical or public-health settings.
A 2023 review found that even the best equations predicted resting metabolism accurately for only 60-70% of people (Lee et al., Nutrients, 2023).
So… How Accurate Are These Numbers Really?
Even with good formulas, real-world factors can easily throw things off:
• Body composition: muscle tissue burns more energy than fat, but equations rarely account for this precisely.
• Activity multipliers: the “1.55 for moderate activity” style factors are rough guesses, not measurements.
• Lifestyle differences: sleep, stress, and recovery all change energy needs day-to-day.
• Tracking variance: food labels, portion sizes, and app databases can each introduce another 10% swing.
That’s why we always say, a calorie calculation is a compass, not a GPS.
How Accurate Are Fitness Trackers, Really?
Wearable devices like Apple Watches, Fitbits, Garmins, and Whoop bands are great for building awareness, but they’re far from perfect when it comes to calorie tracking.
Research from Stanford University found that while most wrist-worn devices were fairly accurate for heart rate, they overestimated calorie burn by an average of 27%, with some readings off by more than 90% (Shcherbina et al., 2017, Journal of Personalised Medicine).
That’s a big gap, especially if you’re basing your food intake on those numbers. It’s one of the main reasons many people struggle with plateaus or unexpected weight gain: the data they’re trusting isn’t as precise as it looks.
Steady-state cardio activities like walking or cycling tend to track closer to reality, while resistance training, HIIT, and mixed circuits are much harder for wearables to interpret accurately. Arm motion, sensor placement, and skin temperature can all throw off the readings.
At The Lab, we don’t dismiss fitness watches, we just use them in context. They’re great for tracking steps, movement patterns, or sleep trends, but not for calculating how many calories you’ve “earned.”
Our approach is simple:
Use your watch to inform your awareness, not to dictate your diet.
How We Define Success in Nutrition Coaching
At The Lab, we see success in nutrition as a skill, not a short-term result.
In the early stages, that often means using numbers. Tracking calories and macros for a couple of weeks is one of the fastest ways to build awareness. It helps people see where their intake actually sits, how different foods contribute to energy balance, and what their macronutrient split looks like in real terms.
But that’s only step one. The goal is to move beyond the numbers. Over time, we teach members how to regulate themselves, to understand portion sizes, hunger cues, and recovery needs without relying on an app.
Because while tracking is a brilliant awareness tool, doing it year-round isn’t realistic or healthy. It can create unnecessary obsession, and it’s not compatible with living a normal, social life. The real win is when someone can enjoy their weekend, eat out, and still stay aligned with their goals because they’ve learned to self-regulate.
When Progress Stalls, What We Check First
Before we change calories or macros, we look at everything else that might explain a plateau.
That means checking adherence first, is the plan being followed as written?
Then we look at training load, recovery, sleep, and stress. Sometimes a client’s outside movement (steps, NEAT, general activity) has dropped without them realising, which shifts the whole calorie equation.
There’s also the physiological side, the body naturally adapts to lower calorie intakes over time. So, a short plateau doesn’t always mean something’s wrong, it might just be your body adjusting before moving again.
By reviewing all these angles, we avoid unnecessary calorie cuts and make smarter, more sustainable changes.
Tailoring Macros to the Individual
Not everyone needs the same macro balance, and not every goal demands the same priorities.
For performance-based clients, such as athletes or those training at higher intensities, carbohydrates play a key role in fuelling sessions and supporting recovery. Endurance athletes in particular need a higher carb intake relative to bodyweight to maintain energy and performance.
For the general population, the split between carbs and fats can be more flexible and largely comes down to preference and lifestyle. What matters most is hitting overall calories and protein consistently, the rest can be shaped around what’s most enjoyable and sustainable.
We don’t use complex carbohydrate periodisation systems at The Lab. While those methods can work, they often add unnecessary complication. Most people get far better results from simply building consistent habits around whole-food meals, balanced portions, and smart fuelling before and after training.
That said, we always consider minimum fat thresholds to protect health and hormone function, usually around 0.6-0.8 g per kg of bodyweight. Fats are calorie-dense, which makes them easier to adjust when needed, but they’re also vital for brain function, recovery, and long-term wellbeing. It’s a fine balance between cutting enough to create a deficit and keeping enough for health.
Common Misconceptions About Tracking
A lot of people assume that success means tracking every gram forever, even at social events, and hitting targets with absolute precision. That’s not the case.
Tracking is a skill, not a lifestyle. We encourage members to use it as a learning tool: spend a couple of weeks logging food to build awareness, then gradually step back as confidence grows.
A 10-15 percent margin of flexibility is completely normal. The goal isn’t perfection, it’s consistency with the big rocks: getting enough protein, roughly meeting your calorie range, and making balanced food choices most of the time.
We use visual tools to help members move away from the numbers when they’re ready, things like portion guides, the “protein-first plate” method, and examples of how to build satisfying meals using whole foods. It’s about understanding principles, not memorising macros.
Nutrition Principles We Coach By at The Lab
Once someone understands the basics of calories and macros, it’s time to focus on principles, the simple, repeatable habits that drive long-term progress.
1. Fuel for the Work Required
Calories aren’t just about bodyweight change, they’re about fuelling performance and recovery. We remind members that if you’re training hard, you need to eat to support it. Cutting calories too aggressively can impact recovery, mood, and performance.
Sometimes that means maintaining calories or even increasing them slightly to make progress in the gym, even when the goal is fat loss. The point is to adjust based on output, not emotion.
2. Protein Anchors the Plate
Protein is the foundation of every good meal plan. It supports recovery, muscle retention, and satiety. We teach members to build meals around protein first, then fill the rest of the plate with carbs, fats, and colourful plants.
It’s a simple principle but a powerful one, it improves meal quality, keeps hunger under control, and naturally helps balance the rest of the diet.
3. Whole Foods First
Real food first, always. That doesn’t mean clean eating or perfection; it just means prioritising foods that keep you fuller for longer and deliver real nutrition.
We use visuals and meal examples to help members understand how whole foods make a difference, fibre, micronutrients, and the satiety effect all play a role.
4. Consistency Over Perfection
You don’t need to hit your targets 100% of the time, 80–90% consistency is enough to make progress.
We help members zoom out and look at weekly averages rather than obsessing over single days. The same way one workout doesn’t make you fit, one meal doesn’t define your nutrition. It’s the average over time that counts.
5. Balance Training and Recovery
Nutrition isn’t separate from training, it’s what fuels it. Under-fuelling leads to fatigue, poor recovery, and increased injury risk. We emphasise sleep, hydration, and post-training nutrition as much as calorie balance.
Food isn’t just fuel, it’s the foundation for better training, better recovery, and a better relationship with your body.
6. Awareness Over Obsession
Our goal is awareness, not control. Tracking, structure, and targets are great tools early on, but the real sign of progress is being able to step away from them and still make confident choices.
When someone reaches the point where they can trust their hunger, recognise portion sizes, and eat flexibly without stress, that’s when we know the process has worked.
Real Coaching Stories That Bring It to Life
Because theory is helpful, but stories make it real.
Am I Eating Enough to Build Muscle?
A client once asked:
“I train hard, but with work and a busy lifestyle, I’m not sure if I’m eating enough.”
They were already doing most things right, eating protein, training consistently, but simply needed a small calorie bump to support recovery and growth. A modest surplus, better protein distribution across meals, and small training tweaks made all the difference.
From Skipping Breakfast to Finding Balance
Another member used to skip breakfast to save calories, then ended up hungry and snacking later. We helped them reframe their routine, starting the day with something simple like yoghurt, fruit, or eggs to support energy and appetite control.
“Once I started eating earlier, I stopped craving sugary snacks. I had more energy, and fewer cravings.”
This small change created consistency, not restriction, and made the process far more sustainable.
Stuck After Losing Weight
It’s normal for progress to slow after initial weight loss.
As explained in our article Stuck After Losing Weight? Here’s What to Do Next your metabolism naturally adapts, daily movement often drops, and recovery can lag.
Instead of pushing harder, we often take a smarter approach:
• A short maintenance phase to reset
• A small calorie reduction via fats if truly needed
• Or simply more movement and sleep consistency
In most cases, progress restarts once those key levers are adjusted, not by slashing calories.
How Nutrition Integrates with Training and Everyday Life
Nutrition doesn’t live in a vacuum. It’s tied to training, recovery, energy, stress, and more.
Start with the Big Rocks
In Feeling Tired All the Time? Start With These Energy Checkpoints we break it down simply:
• Are you eating enough real food?
• Are you hydrating properly?
• Are you sleeping 7–8 hours?
• Is your training load sustainable?
• Are you managing stress?
Before tweaking macros or supplements, we make sure these Big Rocks are in place. Because if one is off, no equation will fix it.
Keep Life in the Equation
Skipping meals might look like control, but it often backfires later with hunger and poor recovery.
That’s why we build flexible nutrition structures, not rigid rules, so members can stay consistent even on busy days or social weekends.
When You’re Stuck, It’s Not Always About More Deficit
Our Why Am I Stuck Losing and Gaining the Same 1kg? post explains it well. Day-to-day weight fluctuations are normal, and short-term stalls don’t mean failure. We teach members to zoom out, assess trends, and make calm, data-driven decisions.
Integration Is the Real Goal
Nutrition drives performance.
Performance justifies intake.
Recovery makes it all stick.
When you realise these systems work together, the pressure to hit the perfect number disappears. Progress becomes about consistency, adjustment, and balance, not perfection.
Key Takeaway
Calorie calculations are useful tools, but only when they’re used in context.
They don’t know how much you slept, how stressed you are, or how many steps you took chasing your kids.
That’s why we always combine numbers with coaching, education, and accountability.
At The Lab Liverpool, we’ll teach you how to understand your nutrition, not just follow it.
If you want to learn how to fuel your training, support recovery, and finally find a plan that fits your lifestyle, get in touch or explore our Small Group Personal Training programme.
References
Roza A. M., & Shizgal H. M. (1984). The Harris–Benedict equation reevaluated: resting energy requirements and the body cell mass. American Journal of Clinical Nutrition, 40(1), 168–182.
Frankenfield D. et al. (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. Journal of the American Dietetic Association, 105(5), 775–789
Shcherbina, A., Mattsson, C. M., Waggott, D., Salisbury, H., Christle, J. W., Hastie, T., Wheeler, M. T., & Ashley, E. A. (2017). Accuracy in wrist-worn, sensor-based measurements of heart rate and energy expenditure in a diverse cohort. Journal of Personalized Medicine, 7(2), 3.
Lee J. et al. (2023). Comparative accuracy of predictive equations for resting metabolic rate: a systematic review. Nutrients, 15(1), 93.
Liu Y. et al. (2024). Comparative analysis of basal metabolic rate estimation equations and measured values in adults. Medicine (Baltimore), 103(30): e37765.
