Why does my calorie goal increase when I log exercise? Or, what is BMR & TDEE?

Wednesday, January 11, 2017

When I first signed up for my online tracker I answered a series of questions. They asked some basic bio-data: age, weight, gender, height etc. They also asked my activity level: Sedentary, Lightly Active, or Active. From that they did some behind the scenes magic and gave me a calorie goal. For this example we will use my numbers. My daily range is 1,500-1,850 calories. Since we are using me as the example I will also add that I am a 52 year old male, 172 cm, and 99 kilos (5’8″, and 217 Lbs). As I add in exercise the number goes up. Unfortunately these numbers come with little to no explanation.

Judging from the number of questions online it would seem that I am not the only one wondering what the numbers are. So I went online and did my own research. I will try and explain it in as plain language as I can and I hope it makes sense.

First and foremost, the range on most trackers does seem to be fairly accurate – so just following their advice should work. If, however, you are like me and want to know “why”, this is why.

There are lots of acronyms, and I will define them as we go. The first thing you need is your BMR: Basal Metabolic Rate (I still read that as “basic” ha ha). That is the calories your body needs just to maintain life functions. If you stay in bed all the time, your body will burn your BMR just to maintain heartbeat, lung function, and brain activity. Eating less than your BMR would be very unhealthy. You would lose weight but it is not healthy, sensible, or sustainable. As an example look at soldiers coming out of prison camps. Sure, they lost weight, but do they look healthy?

I could never find a direct answer on my tracker as to what my BMR is. I used a couple online calculators (there are many) and they all say my BMR is around 1800-1900. You will see a variance in the ranges, depending on the calculator or website used. I am not going to worry about a couple hundred calories one way or the other. These are estimates, ballpark figures, if you will. If you are a professional athlete with a team of doctors and a bunch of machines hooked up to you, then you will get a much more precise number for you. For most of us these estimates are fine. You have to use these numbers as a tool to help you lose weight. These numbers are not carved in stone. They will vary, especially the TDEE, because some of the information used in calculating them is subjective.

Once you have your BMR you use it to determine your TDEE: Total Daily Energy Expenditure. The calculations behind this gets long and the science got boring. Suffice it to say that there are numerous online calculators for it, and the trackers doit automatically for you. The BMR is the baseline to sustain yourself. The TDEE is the total amount of calories you need, in all respects.

The TDEE considers other acronyms as well. Such as the NEAT: Non-Exercise Activity Thermogenesis – This is the energy burned in ways that are not sleeping, eating, or exercise, like typing, fidgeting, etc. Your non-resting but non-exercise caloric needs. The TEF: Thermic Effect of Food – The calories burned to digest what you eat. The TEF is what brings rise to the myth of “calorie negative” foods, foods that burn more calories to digest than they contain. Celery being a prime example. Celery contains 6 calories per stalk and takes about 1/2 a calorie to digest. Low calorie, but not negative calorie. There is no sound science behind negative calorie foods. Lots of weight loss pages tout them, but all the medical sites I found deny their existence. But I digress…

The TDEE also considers your activity level. A very subjective answer. My tracker uses 3 steps: Sedentary, Lightly Active, and Active. All the online calculators I found use 5 steps: Sedentary, Light Activity, Moderate Activity, Heavy Activity, and Very Heavy Activity. It is really not steps but a sliding scale. This is part of what makes the range just a good suggestion. What you call Moderate, others might call Light, or Heavy. It is a subjective answer – so it is imprecise. But good enough for our purposes.

On 3 online TDEE calculators my TDEE ranges from 2,500-2,600. This is the number you work with to determine the desired weight loss schedule. To lose 1 pound a week you need to cut 3,500 calories. Divided by 7 that is 500 calories a day. So to lose 1 pound a week you need to cut 500 calories each day. Either by exercising more or eating less – or a combination of both. Remember we are using the TDEE now, not the BMR. The BMR is used in the calculations and basically ignored after that (other than don’t eat less than your BMR).

I setup my tracker to lose 1 kilo a week (2.2 pounds). That would mean I need to be at a 1,000 calorie deficit from my TDEE, but my tracker said it won’t cut more than 900 for health reasons. Good enough. Almost a kilo a week is still good. For as much as I like the details – I don’t sweat the details. My tracker seems to refigure your TDEE as you log exercise. So each day will be different. Each morning you start with a goal, as I said my daily range is 1,500-1,850. Yesterday I burned 478 calories so my range adjusted up to 1978-2328. If I eat enough calories to stay in that range I should lose the desired weight. On days that exercise less it may stay down closer to your base goal. Today is raining so I will get very little exercise, and my caloric needs will stay closer to the 1,500-1,850. Through experimentation I find the low end of the scale best for me. You have to monitor your logs, weight, and energy level to see what works best for you.

The TDEE is the reason your calorie range will change as you log exercise on your tracker. The TDEE is based on your BMR, plus other calorie expenditures. So the more you exercise, the more calories you burn, and the more you need to eat to stay in the correct range. Under eating is a major mistake that many of us make in our weight loss failures. If you under eat your body will not have the energy needed to perform optimally. At the proper caloric deficit your body will use mostly stored fat for it’s energy deficit. Without enough calories, your body will also feed on muscle and you may lose weight, but you will lose overall health. Even at the proper caloric deficit you will feed off of a combination of stored fat and muscle. Which is why we need to incorporate some strength training in our weight loss plan.

Another way to look at the TDEE is that it is your maintenance caloric needs. If you eat your TDEE you will maintain your weight. Eat more and you gain. Eat less you will lose weight. I can’t wait until I get down to my maintenance diet!

Now that I have a better understanding of the caloric needs, and I have gotten better at portion control, I am beginning to watch the macros closer. With a balanced diet the macros pretty much take care of themselves, but some nudging may be helpful. Eating the right foods, in the right amounts, will give you the energy and strength to sustain your new lifestyle. Too often a “diet” is a temporary fix to a permanent problem. The starvation diets, and the quick fixes are not sustainable. Eat less, eat better, and exercise more is my diet plan. Smart, sensible, and sustainable.

Enjoy your day in paradise,
Tito Tim