Most adults need to eat 300–500 calories below their total daily energy expenditure to lose fat at a sustainable pace. That figure is well-supported by research and the underlying formula is consistent for everyone. But the specific calorie number the formula produces? That part is not one-size-fits-all. Your body weight, age, muscle mass, activity level, and hormonal profile all shape what your personal target looks like and understanding why that's the case is what separates a calorie target that actually works from one that stalls after three weeks.
This article walks you through the calculation, explains the variables that make your number unique, and gives you practical guidance on how to apply it and adjust it over time.
A calorie deficit occurs when you consume fewer calories than your body burns across a given day. When that happens consistently, your body draws on stored energy, primarily body fat, to make up the shortfall. This is the fundamental mechanism behind fat loss, regardless of which dietary approach is being used.
The underlying arithmetic is straightforward. One kilogram of body fat stores approximately 7,700 calories of energy. A consistent daily deficit of 500 calories would, in theory, produce roughly 0.5 kg of fat loss per week. Over time, that compounds into meaningful change.
That said, fat loss is not purely linear. Metabolic adaptation, water retention, shifts in muscle mass, and individual physiological variation all affect the pace and pattern of real-world results. The formula is a reliable starting point, not a guaranteed output and treating it as such is part of using it effectively.
Your Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns across a full day, accounting for everything from breathing and digestion to structured exercise and incidental movement. It is the number you need before any calorie target for fat loss makes sense.
TDEE is calculated in two stages.
Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest, simply to keep you alive. It accounts for approximately 60–75% of total daily energy expenditure and is driven primarily by body weight, height, age, and sex.
The Revised Harris-Benedict equation (Roza and Shizgal, 1984) is one of the most widely used formulas for estimating BMR and remains a standard reference in clinical and applied nutrition settings:
For women: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) – (4.330 x age in years)
For men: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) – (5.677 x age in years)
Once you have your BMR, multiply it by an activity factor to estimate your full TDEE:
The result is your estimated TDEE: the approximate number of calories required to maintain your current weight. To create a deficit for fat loss, subtract 300–500 calories from this figure. A 300-calorie deficit produces slower, more conservative fat loss. A 500-calorie deficit accelerates results while remaining within the sustainable range recommended by most dietetic guidelines, including those from the National Health and Medical Research Council (NHMRC).
Here is where most standard calorie guidance falls short. The formula above applies universally. The number it produces does not.
Several factors mean that two people of identical weight, height, and age can have meaningfully different calorie needs and therefore different targets for fat loss. Understanding these variables is what makes the difference between a target that works and one that needs constant revision.
Muscle tissue is metabolically active. Fat tissue, largely, is not. Two people who weigh 75 kg but carry different amounts of muscle and fat will have different resting metabolic rates and different TDEEs. The person with more lean mass burns more calories at rest, which means their maintenance intake and therefore their fat loss target will be higher.
This is one of the reasons resistance training during a calorie deficit is consistently recommended in the scientific literature. Preserving or building muscle mass keeps your metabolic rate higher and improves the quality of fat loss over time meaning more of what you lose comes from fat rather than muscle.
Your activity multiplier accounts for structured exercise, but a significant portion of daily energy expenditure comes from something less visible: Non-Exercise Activity Thermogenesis, or NEAT. This covers the calories burned through all the movement that is not deliberate exercise such as walking, standing, fidgeting, household tasks, and so on.
NEAT varies enormously between individuals. Research published in Science by Levine and colleagues (1999) found that NEAT differences between people could account for up to 2,000 calories per day. Two people who both sit at a desk for eight hours but move differently through the rest of their day can have vastly different TDEEs, even if every other variable is the same.
Hormones including thyroid hormones, insulin, leptin, and cortisol all influence metabolic rate, appetite regulation, and fat storage. Conditions such as hypothyroidism or polycystic ovarian syndrome (PCOS) can meaningfully reduce metabolic rate or affect how the body processes and stores energy, making standard calorie calculations less accurate for some individuals.
If you have been genuinely consistent with your calorie target for three or more weeks and seen no change in body weight at all, a conversation with a GP or accredited practising dietitian is worth having. A calculation is not a diagnosis.
The body responds to a sustained calorie deficit by gradually reducing its energy expenditure a process called metabolic adaptation. Research led by Dr Rudy Leibel at Columbia University demonstrated this effect clearly, and it was further highlighted in the well-documented follow-up study of The Biggest Loser participants published in Obesity (2016), which showed that contestants experienced significant reductions in resting metabolic rate that persisted years after the show.
In practice, someone who has spent years cycling through calorie-restricted diets may have a resting metabolic rate that sits below what the formula predicts. Their calorie target needs to account for this, and may need to start more conservatively than the standard formula suggests.
This is not a permanent state, and it does not mean results are impossible. It means the starting calculation is a hypothesis to be tested and refined, not a fixed prescription to follow indefinitely.
Reaching a calorie target is the primary driver of fat loss, but the composition of those calories matters too, particularly protein.
Research consistently shows that higher protein intake during a calorie deficit helps preserve lean muscle mass, supports better satiety, and slightly increases the thermic effect of food (the calories burned simply through the process of digestion and absorption). The current evidence base supports a daily protein target of 1.6–2.2 g per kilogram of body weight when eating in a deficit, as summarised in a 2017 meta-analysis published in the British Journal of Sports Medicine.
For a person weighing 70 kg, that translates to approximately 112–154 g of protein per day. Reaching that target within your calorie budget requires some planning, but it meaningfully improves the quality of fat loss you lose proportionally more fat and less muscle compared to a lower-protein approach at the same calorie intake.
Apps like INCHECK FIT are built around this principle, generating personalised meal plans that automatically hit both calorie and protein targets for each user without requiring them to do the calculations manually.
Knowing your number is only useful if you can apply it consistently. These principles make that considerably more achievable in practice.
Use weekly averages, not daily perfection. A daily target of 1,600 calories equals 11,200 calories per week. Whether you hit exactly 1,600 every day or vary between 1,350 and 1,900 across the week matters far less than the weekly total. This flexibility is well-supported by research and makes consistency significantly more achievable for most people.
Do not rely on exercise calorie burns to offset intake. Fitness trackers and gym equipment consistently overestimate calorie expenditure during exercise by 20–93%, according to a 2017 study from Stanford University. Using those figures to justify eating more introduces significant error into your calculations. Your TDEE already accounts for your activity level; treating structured exercise as a calorie bank tends to undermine progress rather than support it.
Build meals around protein first. Protein is the most satiating macronutrient. Anchoring each meal to a protein source before filling in carbohydrates and fats makes it considerably easier to stay within your calorie target without persistent hunger.
Expect the number to need adjusting. No formula is perfectly accurate for any individual. If you have been consistently hitting your calorie target for three or more weeks with no change in body weight, reducing your intake by 100–150 calories and reassessing over the following two to three weeks is the appropriate response. The target is a starting point, not a permanent prescription.
Calorie targets are not static. These are the clearest signals that a change is needed:
No movement on the scale after 3 weeks. If you have been genuinely consistent and the scale has not shifted at all, your actual TDEE is likely lower than calculated. Reduce intake by 100–200 calories and monitor for another two to three weeks before drawing conclusions.
Constant hunger or persistent fatigue. A deficit that is too aggressive typically more than 750–1,000 calories below your TDEE can cause significant hunger, mood disruption, and accelerated muscle breakdown. If this describes your experience, your target is probably too low. A smaller deficit applied consistently over a longer period produces better fat loss outcomes than an aggressive deficit that proves unsustainable within weeks.
Losing weight faster than 1 kg per week. If you are not significantly overweight and are losing weight rapidly, you may be losing muscle alongside fat. Reducing the deficit slightly and ensuring your protein target is being met will help preserve lean mass and improve the long-term quality of your results.
In each of these scenarios, the approach is the same: collect two to three weeks of honest data, make one measured adjustment, and assess the outcome. Changing multiple variables simultaneously makes it impossible to know what is actually driving the result.
Last reviewed: March 2026 by the INCHECK FIT nutrition team.
