TDEE, BMR, RMR....help!

[Aebrown]

In the past I've had good luck with losing weight on a calorie deficit. I use MFP and Fitbit to track and log everything. 

I'm trying to lose (again) and this time discovered TDEE, BMR, and RMR and now I'm just overwhelmed. To be honest I'm terrible at math and this is just all too confusing. 

I was under the impression that a 1000 calorie deficit is fine but after using all these calculators, I never really got that number. I mean, I'm very active, I burn 2800-3200 calories a day, but all of these calculators are telling me I shouldn't eat more than 1600-1700 calories a day....that's too low based on what I burn, right? If I were to burn 5000 a day, wouldn't I need to eat 4000? Is that not how it works? I'm so confused! 

I am female, 25 years old, 5ft9inches, 165 pounds. 

My RMR is 1736.

BMR is 1571.

My TDEE is 2337

.....if any of that helps. 

Also, do my calories need to be the same every single day? How am I supposed to have a deficit every single day but yet I need rest days? Obviously I would just need to eat less in order to keep the same deficit while taking a day off, right? 

[Dominique · Accepted solution]

How much you "need" to eat depends on your goal in terms of weight management: do you want to maintain your weight, lose some, or gain some? If you want to lose, you do need to eat less than what you expend ("burn"), i.e. be in a caloric deficit. The size of your deficit will (should) determine the pace of your weight loss: a 1000 calorie deficit (on a daily basis) should result in a loss of 2 lbs per week, a 1000 deficit in a loss of 1 lb per week. You don’t have to be in the same deficit every day, or even to be in a deficit at all everyday. These things accumulate: a cumulative deficit of 3500 calories will result in a loss of 1 pound.

Then you may want to distinguish between the TDEE reported by Fitbit (total calories burned) vs. your actual energy expenditure. When you write "I burn 2800-3200 calories a day", it should be: "my Fitbit says I burn ...". Estimating energy expenditure with an activity tracker isn’t exact science, there’s a margin of error. Many people tend to find their actual expenditure is lower than what Fitbit reports. How do they know? Because they’re also logging their intake and they notice (the scale is telling them) they’re losing less than what Fitbit predicts.

It’s usually advised not to eat below your BMR. By that standard, if your TDEE is 2337 and your BMR 1571, a deficit of 1000 would be excessive. You may therefore want to consider a smaller deficit (e.g. 500 or 750). You will/should be losing, but more slowly. However, you will likely not "plateau" as quickly as with a more aggressive deficit. Given you’re already in the normal weight range for your height, you can afford a slower approach.

[bikerhiker]

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@Aebrown wrote:

In the past I've had good luck with losing weight on a calorie deficit. I use MFP and Fitbit to track and log everything. 

I'm trying to lose (again) and this time discovered TDEE, BMR, and RMR and now I'm just overwhelmed. To be honest I'm terrible at math and this is just all too confusing. 

I was under the impression that a 1000 calorie deficit is fine but after using all these calculators, I never really got that number. I mean, I'm very active, I burn 2800-3200 calories a day, but all of these calculators are telling me I shouldn't eat more than 1600-1700 calories a day....that's too low based on what I burn, right? If I were to burn 5000 a day, wouldn't I need to eat 4000? Is that not how it works? I'm so confused! 

I am female, 25 years old, 5ft9inches, 165 pounds. 

My RMR is 1736.

BMR is 1571.

My TDEE is 2337

.....if any of that helps. 

Also, do my calories need to be the same every single day? How am I supposed to have a deficit every single day but yet I need rest days? Obviously I would just need to eat less in order to keep the same deficit while taking a day off, right? 

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The rule is that you shouldn't be eating less than your BMR; so if you do nothing for that day and your body burns 1571 calories, then you should be eating 1571 calories to net zero your BMR.  If you eat less than your BMR, then you can cause your metabolic rate to decrease and encourage the process called glyconeogenesis, where your body starts converting lean muscle mass into glucose to use a fuel since you are not providing enough fuel for the body to operate.  You are also in the danger of getting more sick often since your pulmonary circulatory functions and your immunity systems are impaired.

However, based on your current weight and height, your BMI is around 24.4, which is considered normal and healthy for a female like yourself.  So I am assuming that your focus in losing weight is to achieve a goal other than health.  If that is so, then you need to focus on several things first to achieve an effective calorie deficit, since your BMI is within the normal range. 

1, Lifestyle

2, Food

3, Rest

It gets harder to go towards a lower BMI rate; or a lower body fat since a female needs a higher percentage of body fat for reproductive purposes and hormonal regulation as men do not need to do.  So be very careful not to compare yourself to a man of your similar age to achieve similar body fat and similar BMI.

Having said that; if you had truly reduced your body fat, then you would have also reset your body fat setpoint as well.  This new body fat setpoint regulates your new BMR, RMR and your TDEE and therefore once you resume eating normally to satiety after a caloric deficit, you will no longer gain weight.  Or if you eat too much in a party or in a conference or cruise ship, your gained weight can easily be shed through a conservative 500 calorie deficit to lose a 1lb and your body will naturally reset back to your homeostasis weight, which is the weight you started before the caloric deficit or after you completed the caloric deficit.  If you reset the body fat setpoint correctly, your new weight will become permanent.

Unfortunately, most people do the opposite and do drastic caloric reduction through diet and exercise and while that may work in previous weight loss attempts; eventually the body will build resistance.  It learns how you lose weight and since you didn't let it settle to the body fat setpoint long enough, the body will develop a more resistant immunity to the next weight loss.  Done enough, it takes even more drastic measures to lose weight.  This is the same analogy as with bacteria and viruses; that eventually even the most toughest anti-viral and anti-bacterial medication will not be effective against those pests that will develop immunity against those medication.  Your body with a certain body fat setpoint will do exactly the same; which will then require you to drastically cut your diet to eat much below your BMR to achieve some results.  Not a good idea to eat below BMR, but this is what will happen if you didn't reset the body fat setpoint.

So the key to resetting the body fat setpoint is actually to find a way to allow your body to use a higher proportion of body fat as your fuel source.  And in order to achieve that, you need to find a way to lower the stress level of your body and mind to allow your body to naturally use your body fat as part of the fuel source.  So as I referenced lifestyle as the first priority.  Lifestyle has a lot to do with how much body fat you keep.  A stressful and toxic lifestyle will not promote lower body fat, because any stress caused by the lifestyle you are in will cause your body to react by causing hormonal changes to secrete Cortisol, which then raises insulin level and lower blood sugar level.  Too much exercise does the same.  So what happens next is that, while you may have burned 3000 calories through exercise, most of which are going to be replaced by carbohydrates -- mostly simple as low blood sugar requires immediate infusion of glucose into your bloodstream, or you go into hypoglycemia -- not fun and pleasant.  So even the choices of food will have something to do with your lifestyle.  A stressful lifestyle usually will make you feel attracted towards food that are high in carbohydrates, but lower in nutritional value.  Especially if you are eating close to your BMR; lowering your calories will guarantee that you won't have enough minerals, vitamins, nutrients, dietary fat and fibre in your diet.  So you can see why 1 in 2 women in North America suffer from a bone disorder called "Osteoperosis".  Their bones are so fragile that it breaks even if you bump into something.  This is what will happen to those people who chase beauty and looks and pay for those decisions down the road!!  It's very difficult to reverse Osteoporosis.  When you are young, you want to consume a lot of nutritional food to allow growth for your body.

Having said that; stress is a challenging especially within the stage of your life.  You are young and there are a lot of challenges that you face as an individual.   So in order to lower stress level, you also need to allow your body to rest.  Having enough rest allows your body to recover and also burn fat during your sleep, if you get enough deep long sleep like 7-8 hrs/day.

Sometimes, people focused too much on a caloric deficit, but not enough on the function of the body and how the body burns body fat as fuel.  That is more important in losing weight rather than trying to eat less.

Hope this helps.