How To Use BMR To Lose Weight


There are several ways to track your calorie intake and lose weight. By far, the most effective ways are counting calories and following a ready-made diet plan. They are precise, accurate and as long as you are consistent you can get super lean.

The most confusing part of counting calories is establishing a benchmark, or in other words, your daily calorie needs. Because to know how many calories you can eat, first you must know how many calories are being burned.

In this article I will show you how to use your BMR to lose weight and establish when you’re in calorie deficit.

What Is BMR?

BMR stands for basal metabolic rate. BMR is the largest part of total energy expenditure comprising up to 70% and is defined as the minimum energy cost during absolute rest for basic processes like breathing, oxygen transportation, cognitive thinking, and blood circulation.

About 4.82 calories are being transferred when 1 liter of oxygen is consumed. This means the more oxygen we consume, the more calories we will burn. And some tissues, like muscle mass, require a gigantic amount of oxygen to survive.

So the more lean mass we have, the more oxygen we need, the more calorie we burn.

Measuring BMR is nothing else than measuring the amount of oxygen that we consume at rest. This way we know exactly how many calories the body “burn”.

As you can imagine, the amount of oxygen consumed by people will vary.

There are couple way to estimate BMR:

  • Indirect calorimetry

Those are assessed in the laboratory and field settings using calorimeters and masks to collect expired air and measure calories consumed during the 24-hour.

  • Direct calorimetry

Those are assessed in the air-tight chamber-based systems where energy expenditure is recorded by expired air and the rate at which heat is generated by the body.

Those are the most accurate and precise ways to really measure BMR.

However, they are not very practical for everyday use.

There are few predictive equations that estimate energy expenditure.

They are far less accurate but reasonably accessible (source).

  • Estimate BMR is by using Mifflin formula .
  • Men = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
  • WOMEN = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161

Note: Those estimates can very up to 20-30% for young healthy people, and even more for other groups.

Related article: Should I Eat The Same Amount Of Calories As My BMR?

What Is TDEE?

TDEE stands for total daily energy expenditure. This is the number of calories that our body uses in a 24-hour period. TDEE can be divided into basal metabolic rate (BMR), the thermic effect of food (TEF), and physical activity energy expenditure (PAEE).

Total energy expenditure account for every single calorie need:

  • Digestion
  • Breathing
  • Nutrient transport
  • Gut motility
  • Protein synthesis
  • Enzymatic production
  • Physical activity

TDEE can be further divided into more sub-categories:

  • NEAT (non-exercise activity thermogenesis)
  • EAT (exercise activity thermogenesis)
  • TEF (thermogenic effect of food)

In other words, this is your energy out. Nothing is left behind.

And once we know what is your energy out, we can then focus to optimize of your energy in aka calorie intake.

But first.

Should I Use BMR or TDEE To Lose Weight?

In general, to lose weight it is better to use BMR than TDEE. Basal metabolic rate accounts for around 70% of your daily calorie needs, and therefore, eating around this number will put you in the calorie deficit, regardless if you’re physically active or not.

Let me give you two examples here.

TDEE Calculator To Lose Weight

Let’s say that you’ve calculated your TDEE in one of the online calculators.

Your number went around 3000 calories and you good to go. You decided to lower your calorie intake by 500 calories and your new diet is made of 2500 calories.

3 weeks later and you haven’t lost any weight.

Why?

Because measuring your metabolism is tricky.

Unless you’re living in the laboratory where you’re hooked up with a metabolic cart to measure your oxygen input every minute for 24-hours, we cannot really know for sure your exact metabolic rate.

All the tools that measure metabolism are just estimates.

And they can be off by 20–30%.

So by estimating your total calorie expenditure and designing your meal plan around this number (taking into the considerations that estimates are just estimates) you may or may not be in the calorie deficit.

BMR Calculator To Lose Weight

Now let’s say you’ve calculated BMR as a benchmark. Still, calculations can be off for as much as 20-30% but because BMR is only 70% of your total energy expenditure.

This means even if it’s off, you still get to a calorie deficit.

Regardless if you’re physically active or not.

Why?

Because if you’re consuming 70% of your calorie intake, the remaining 30% (TEF, NEAT, EAT) is enough to put you in the calorie deficit.

Should I Eat Around My BMR To Lose Weight?

In general, eating around your BMR will create a calorie deficit and lead to weight loss. Basal metabolic rate is an estimation of around 70% of your total daily energy expenditure. Eating around this number will put you in the approximate 30% calorie deficit.

So even if your BMR calculations are off, you still will be able to stay in a negative energy balance.

Where if you would use TDEE as your reference, you could think you’re in a calorie deficit, where in fact you could be gaining weight.

There are some things to consider when you’re calculating your BMR:

  • It take time to see first results

Remember weight loss done by calorie deficit is a process, not an event.

This means you won’t know if you’re making progress until few weeks along the line.

And if you noticed that you can’t see results, don’t be harsh on yourself.

Change approach and try again.

  • You may be underestimating your calorie intake

Unless you’re tracking every bite and you’re honest with yourself, it is very easy to think we eat less, where in reality we may just eat the same or only slightly more.

The perception of food intake usually differs from the actual food intake.

If you want to learn more about those differences, I’ve written an article about why am I not losing weight in a calorie deficit.

What Happens If I Eat Less Than My BMR?

In general, if you eat less than your BMR, you will create calorie restriction and negative energy balance that leads to weight loss. By eating less than your basal metabolic rate the body will enter into a calorie deficit and start using for as the main source of energy.

As a general rule, you can eat less than your BMR to create a calorie deficit.

Restricting calories and eating less than your BMR can put you into negative energy balance and drive weight loss, even without tracking your calories burned from physical activity.

In other words, by eating below your BMR you’re 100% sure that you’re actually creating calorie deficit.

Which leads to handsome weight loss.

Eating Below BMR Not Losing Weight

In general, If you’re eating below your BMR and not losing weight is because you’re overeating. You may underestimate your calorie intake, you overestimated your physical activity, or you’re too early in the process to start seeing the results.

Also bear in mind that those BMR calculations are only the estimates.

And if you’re really meticulously tracking every bite and still not losing weight, reduce your calorie a little bit more, or add more low-intensity physical activity.

Conclusion

In general, you can use BMR to estimate the number of calories needed to stay in a calorie deficit. Bear in mind that those numbers are only the estimates and they are not definite.

They are good enough as a benchmark and should be taken with a large grain of salt in your daily calorie calculations.

Michal Sieroslawski

Michal is an exercise physiologist (MSc), nutrition coach, Ashtanga teacher, and fitness blogger. He shares his successes and failures to help busy men and women squash down 20, 50, or even 100 pounds of fat without leaving their home.

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