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5 reasons your calorie deficit (probably) isn't working

5 reasons your calorie deficit (probably) isn't working

On paper, losing fat and getting lean sounds straightforward: just eat less than you burn. But if it were that easy, we’d all be sporting rippling six-packs. The truth is, even with the best intentions, it's easy to get it wrong.

Here are 5 common mistakes that you may make regarding your calorie intake and how you can avoid them to shed body fat successfully.

1. Setting calorie needs incorrectly

The first hurdle you may encounter is inaccurately setting your calorie goals. A common strategy is to use an online calculator to determine your resting metabolic rate (RMR), and then establish a caloric deficit of 250–500 calories as your daily intake.

This approach drastically oversimplifies critical components of your metabolism, such as your physical activity (calories burnt through exercise) and non-exercise activity thermogenesis (NEAT) (calories burnt through activities of daily living). To determine your total daily energy expenditure (TDEE), consider all these components and establish your caloric deficit. This ensures a sustainable and effective diet rather than a fast track to frustration and potential metabolic slowdown.

For example, my resting metabolic rate (RMR) is around 1,980 kcal daily. I exercise 4–5 times weekly and walk 9,000–13,000 steps daily. This all contributes to my estimated total daily energy expenditure (TDEE), which is around 2,990 kcal. If I wanted to enter a caloric deficit to lose about half a kilogram of body fat per week, I'd start by setting my calories between 2,400–2,500 kcal.

In this example, if I'd set my caloric deficit from just my resting metabolic rate (1,980 kcal), I would have set my daily caloric intake down to 1,480 kcal. That few calories would likely lead to muscle loss, low energy, and slow down my metabolism, and I simply wouldn't be able to sustain it.

2. Staying in a deficit for too long

It's important to remember that your body is clever and highly adaptive. As you lose weight, your body will adapt to burn fewer calories. What worked at the start of your journey might not work forever.

Maintaining a prolonged caloric deficit can prompt your body to enter a sort of "survival mode", where it will adapt to slow down your metabolism to conserve energy. This natural response can make your initial calorie deficit less effective over time, turning fat loss into a challenging moving target.

Alternating between 8–12-week periods in a deficit and eating maintenance calories (where your intake is equal to calories burned) can help "reset" your metabolism. This cycling prevents your body from getting too comfortable with a lower calorie intake, thus maintaining a healthier metabolism and facilitating continued fat loss.

A table showing how a 20-week nutrition cycle might look like,

Next time you observe a plateau in your fat-loss journey, consider increasing your calorie intake to maintenance levels for 1–2 weeks to help rejuvenate your metabolic rate and give you a psychological break before reentering a deficit.

3. Eating your burned calories

It’s tempting to treat yourself after a good workout, thinking, “I’ve earned it!” While your fitness tracker is a helpful tool to report daily steps and minutes of physical activity, it's not quite there yet in accurately tracking how many calories you've truly burned. A couple of studies have found at least a 27% margin of error in calculating calories burned (with some reporting up to 93%!)

It's important to avoid the common pitfall of "earning" extra calories and then thinking you can consume additional calories without consequence. Basing your daily caloric intake on the estimations of your fitness tracker may lead to you consuming a greater number of calories than you should. So, the advice here is simple: stick to your planned caloric intake and adjust it based on actual changes in your body weight, not on estimates.

4. Swinging between extremes

Strategies for creating a caloric deficit often swing between two extremes: restricting daily caloric intake severely without increasing activity or attempting to "out-exercise" poor dietary habits. However, neither approach is sustainable or effective in the long term.

A picture depicting how a happy medium between diet and exercise should be achieved when trying to lose fat.

The best strategy is to find a happy medium that combines moderate dietary restriction with manageable increases in your weekly physical activity. It’s less about never eating the foods you love or occasionally missing a workout and more about consistent, balanced habits that emphasise the importance of a healthy lifestyle without overreliance on one or the other.

Tracking and monitoring your daily caloric intake, weekly weight averages, body measurements, and taking progress photos are helpful ways to provide the objective data you need to make informed adjustments to your diet, ensuring continued progress toward your goals.

5. Overrating your diet

Finally, many people think their diet is better than it is. When asked, most people will say that they eat pretty healthily, but it's a different story when you dig a little deeper. The odd snack here and an extra alcoholic drink there can all add up, nudging you out of your calorie deficit. Real progress requires honest and accurate tracking of not just the quality but the quantity of food you consume, leveraging tools like food scales and diet-tracking apps to ensure accountability daily.

If the idea of tracking your calories and macros is daunting, I recommend simply tracking your diet for seven days. Half the battle of losing fat and getting your diet under control is awareness of what you eat and how many calories those foods contain. Here's an example of a three-step process you can follow:

  1. Download MyFitnessPal and sign up for their free 30-day premium trial. Plan which week within that trial period you will track your calories and macros.

  2. On day 1, before you eat anything, weigh yourself and log your weight.

  3. Track your calories and macros throughout the week—be as honest and accurate as you can.

  4. On day 7, before you eat anything, weigh yourself and log your weight again.

  5. Review your data. Identify trends in your eating, which foods might prevent you from hitting your daily caloric deficit, and consider calculating the average of your daily intake to see if what you ate caused you to gain or lose weight (using your weights from days 1 and 7).

Would you like to discuss how you can start working towards sustainable, healthier habits? Book a free 30-minute consultation with me to discuss your fitness and how we can collaborate on clear and effective goals to help you get there. If you'd like to receive a steady stream of free weekly advice, tips, and guides about fitness, consider subscribing to Root Fitness and following me on Instagram.


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