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Ask the Trainer: How many calories do I need to lose weight? What about my activity level?

I got a great question this week, and realized it deserved an answer that everyone could read.  The question was about how a person’s activity level influenced how many calories they needed– as in “I do this, this, and this during the week. How do I know how many calories to figure in?”

Woman Stretching with pained look on her faceThe short answer is: Most people are better off not using an activity multiplier at all. But most people are also hugely overestimating the calories they burn during the course of a day and in their workouts.

The long answer is: Instead of using a potentially VERY inaccurate calorie multiplier, use your BMR instead. BMR (Basal Metabolic Rate) is the number of calories it takes to keep your body alive at complete rest. This number is based on your height, weight, gender, and age.  Go here to determine your BMR.  (Note: this post contains general guidelines!  For various reasons, this might not work exactly for you, but it’s a pretty good starting point for most people!)

Let me show you some cool math, using my numbers. My BMR (I’m 5’3, 36, and 155lbs– and of the “pink” variety, but you knew that from the pictures). My BMR is 1340 calories per day. This number includes what it takes for my body to keep my heart beating, digest my food, heal my wounds, blink my eyelids, repair my muscle tissue, etc.

If you want to lose a pound of body fat, you need to decrease 3,500 calories. If you wanted to lose one pound per week, you’d want to decrease 500 calories each day. (3500/7=500)

If you want to use an activity multiplier, you’d take your BMR and multiply it by:

  • 1.2 for sedentary (this is most people! Even if you are walking around during the day, and taking care of your family etc.)
  • 1.3 for lightly active (this is people who are walking or training with some intensity 4+ times per week.)
  • 1.4 for moderately active (If you’re at this level, you have an active job– and you’re really hustling in the gym 5+ times per week. Think: intensity. )
  • 1.6 for very active people (The only person I know who falls into this category is my trainer, who is also a contractor– and trains with more intensity than most 25 year olds.)

[Note: these aren’t what you’ll find in books, etc. These come from my Trainer, who is master certified and has 42 years of experience. After using the “standard” formulas and not seeing any changes in his clients, he devised these which produced better results.]

But going back to my example, I’d take my BMR (1340) and multiply it by 1.4 , which would give me 1876 calories per day. If I wanted to lose 1 pound of fat per week, I’d want to subtract 500 calories per day, which would leave me 1376 calories– which is pretty close to my BMR.

Make sure you’re understanding this: Your BMR makes up the vast majority of your caloric needs. Everything you do in life, from walking around at your job, to picking up the kids from soccer, to grocery shopping, to training in the gym is not contributing much to your caloric needs. This is why it’s impossible to out train a bad diet.

Consider this: a 150 pound person walking about 3 miles per hour– or a 20 minute mile– is burning about 120 calories per half hour. If she did this three times a week, she’d burn 360 calories per week. Annnnnnd, it would take her 10 weeks to lose 1 pound. If the same 150 pound person was strength training with a 90 second rest between sets, they’d burn 188 calories per 30 minutes. If they were training how I train me and my clients, with a 40 second rest between sets, they’d be burning 382 calories per 30 minutes.

But even at 382 calories three times per week, it would still take almost 3 weeks to burn the 3500 calories in a pound. If you did that kind of training five times per week, it’d still take two weeks to lose a single pound.

Annnnnd most people aren’t training with anywhere near that kind of intensity. They play on their phones, or talk during sets, or find ways to get lots of rest. Most people are burning closer to 250 calories per workout (because, you know, public service announcement: the time spent in a gym does not equal training time! I see it all the time when I’m on the gym floor.)  I push my clients hard during classes, and they always want to throw things at me when I tell them they are burning 250-350 calories TOPS during a class.

My recommendation is not to think of your activity (including gym or classes) in terms of assisting in your weight loss. There are so, so many benefits to exercise, but it’s not doing a great job of helping you burn calories while you’re doing it. What does help you burn calories is developing lean muscle, which you will only do by strength training with an appropriate intensity. Having lean muscle actually increases your BMR, which burns more calories even at rest.

Vintage housewife with vacuum
Isn’t this how you look when you do housework? Yeah, me too…

The problem with figuring your “activity” calories into your caloric needs is that most people dramatically overestimate the amount of calories they burn (and also hugely underestimate the number of calories they are consuming.) The other thing it does is creates kind of a “loophole” thinking, where you decide to reward yourself for all your hard work. You determine that you “deserve” a treat, but more often than not, people treat themselves with more calories than they just burned. This happens not just with a workout, but say you spent a day spring cleaning. You had to have burned at least 1,000 calories, amiright? Trust me, I get it.

If you’re using an app like MyFitnessPal (which I like and  recommend), ignore the extra calories it gives you for your activity.  This allows you to focus on the calories your body needs without getting into the sabotaging trap of rewarding yourself for exercise.

I had to learn this lesson the hard way. 250lb pound me wanted to get and eat every calorie she could.  But I wasn’t getting anywhere.

Skip the “bonus” activity calories and activity multipliers! They may be sabotaging your success MUCH more than you realize.


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