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Should I Count Calories?
What You Need To Know About Counting Calories

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What is a Calorie?

A calorie is a unit of energy. Specifically, a calorie is the amount of energy required to heat up 1 gram of water by 1 ℃. Technically speaking, each “Calorie” in food, denoted by the big “C” is equal to 1,000 little “c” calories, but that’s besides the point. The question we should ask is, why is a calorie defined as the amount of energy it takes to heat water?

It all has to do with how calories are measured in food. The technique used to measure the calories in, say, a banana, is called bomb calorimetry.

Literally, you take the banana, place it in a chamber surrounded by water, and blow it up. KABOOM! Energy is released from the combustion into the surrounding water, and the number of ℃ the surrounding water is heated tells us how many calories are in the banana. But can you apply this value to human biology? Well, not really.

How Do We Extract Calories from Food?

Our bodies don’t extract energy like bomb calorimeters. Once the nutrients in our foods make their way to our cells, energy is extracted in a more sophisticated manner than simple combustion.

Food is methodically broken down by an orchestra of enzymes to generate cellular building blocks and liberate electrons that can then be systematically harvested for energy by mitochondria. Jargon aside, we are not bomb calorimeters. Not even close!

What’s more, for every you cell in your body, there is at least one bacterial cell residing in your gut’s microbial ecosystem that also has a role in extracting energy from the food you eat.

Should I Count Calories? What You Need To Know About Counting Calories

Why We Can't Accurately Calculate Calories in Foods

Since we all have different “microbiomes,” we all extract energy from food differently. As an extreme example, if you were a gorilla with a gorilla’s microbiome, you could get 60% of your calories from fiber ( 1)!

True, we aren’t gorillas, but the concept is the same. We each have unique microbiomes and each extract energy from food differently (2). Since we were talking about fiber, let’s use fiber as a case in point. Although fiber is thought to contain no calories, we can indeed extract calories from fiber (or, more correctly, our gut bug friends can for us), in the form of short chain fatty acids ( 3).

As a goofy thought experiment, let’s do some math! That gorilla paper I referenced earlier states that humans can get somewhere between 2 and 9% of our calories from fiber ( 1). If you scale that 7% difference to a 2,000 Calorie diet, that’s 140 calories per day or 51,100 Calories per year. If you want to visualize that, it’s about the equivalent at 64 sticks of butter (as measured by bomb calorimetry).

Obviously, that’s just a goofy thought experiment, but it proves a point: humans are heterogeneous, specifically with respect to our microbiomes, and that complicates the calculation of “calories in.”

Let’s play devil’s advocate and assume that we can perfectly measure calories by blowing up bananas and apply those caloric values to human nutrition. Then would we be able to count calories? Still no. At least in the United States, the Food and Drug Administration’s Guidance for Industry allows for a 20% margin of error on nutrition labels ( 4). Even if food companies actually abided by this law, which many don’t, that would amount to a 400 Calorie error on a 2,000 Calorie diet.

So, let’s summarize. You can’t count calories eaten accurately because:

  • you’re not a bomb calorimeter,
  • you have a unique microbiome, and
  • nutrition labels aren’t accurate.

You can’t count calories eaten accurately because you’re not a bomb calorimeter, you have a unique microbiome, and nutrition labels aren’t accurate.

Should I Count Calories? What You Need To Know About Counting Calories

Why We Can't Accurately Calculate Calorie Expenditure

That’s only half of the equation. Advocates of strict calorie counting provide the logic that calories in – calories out = weight gained.

We’ve talked about calories in, which can’t be accurately measured, but what about calories out or burned?

Here, things get even more messy. One could write an encyclopedia on the topic of why measuring calories burned in humans over an extended period of time is so complicated, but I’ll just mention a few highlights.

To begin, physical exercise only accounts for a tiny fraction of total calories burned for most people. Much more energy is spent on the biological processes of temperature regulation, running your brain, and digestion. Furthermore, “non-exercise activity thermogenesis,” or NEAT, also burns more calories in a day than exercise for most people.

NEAT refers to those physical movements that are separate from exercise, like maintaining good posture or bouncing your leg or gesturing with your hands. NEAT activities amount to far more, in terms of calories, than the 30-60 minutes a person might spend at the gym and is enormously variable among people.

In one study, published in the prestigious journal Science, 16 healthy weight individuals were hyperfed 1,000 Calories per day more than their estimated need for 8 weeks. Quoting from the paper, “Changes in NEAT accounted for the 10-fold differences in fat storage that occurred and directly predicted resistance to fat gain with overfeeding.” ( 5) I’m not even going to digest that for you. Just pause, and think about it!

Now, a question: Do you know people what are fidgety or bounce their leg a lot? Are they skinny?

Perhaps most importantly, the human hormonal system governs how energy is distributed and used. Over the long term, this is enormously important. Your hormones determine if you expend energy or store it. And, if you store it, your hormones determine how you do so, as fat or lean muscle.

Because fat and muscle mass impact hormones, this then creates a cycle. Your hormones determine how your fuel is partitioned. The partitioning of fuel effects your hormones and your metabolic rate, and so on. It becomes a dance among insulin, testosterone, estrogen, ghrelin, thyroid, muscle, and fat that makes counting calories a futile effort over the long term.

So, let’s summarize. You can’t count calories burnt accurately because:

  • Exercise contributes to a small proportion of calories burned, compared to other functions.
  • Your body adjusts NEAT to adjust calories burned.
  • Your hormones determine if you expend energy or store it, and if you store it, how you do so.

You can’t count calories burnt accurately because exercise contributes to a small proportion of calories burned, and your hormones determine if you expend energy or store it.

Should I Count Calories? What You Need To Know About Counting Calories

Count Calories Cautiously

Having said all that, this little blog isn’t going to stop calorie counters from counting, at least not without a viable alternative. So, here are a few suggestions to try instead if you want to lose weight:

Alternative 1: Count Carbs

It’s no secret anymore that the key to controlling weight is controlling carb intake (here's an app for that). In fact, it’s been shown than trading carb calories for fat calories increased “calories out” by about 52 Calories per day for each 10% swap (i.e., 200 carb calories for 200 fat calories on a 2,000 Calorie diet) (6).

Take as many net carbs (exclude fiber) as you’re eating right now and cut that number in half OR reduce your net carbs to 20 grams per day.

Alternative 2: Count Meals

Snacking is the devil when it comes to weight gain. In addition to reducing carbs, you can reduce your levels of fat-storing insulin by eating less frequently.

Try counting your meals or “feedings.” Anytime you eat something with macronutrients, that’s a feeding. Play meal golf as see if you can hit a birdie or two meals per day (par would be 3, given breakfast, lunch, and dinner).

Alternative 3: Count Hours

Try time restricted feeding or intermittent fasting. Starting with eating only inside a 12-hour eating window. Then see if you can reduce that window to 10, 8, or even 6 hours. I find, for a lot of people, this is easier than it sounds. Once you have your window determined, decisions become easy. It’s outside your window, therefore no food. Your body instead must rely on your stored body fat. Don’t worry, it learns.

Alternative 4: Count Glycemic Index

If the above alternatives sound way too strict for you, and you’re not someone who intends to go low-carb or keto, then perhaps try just eating carbs that are lower in “glycemic index” (GI).

The GI of a food refers to how much it spikes your blood sugar. (If you’ve also heard the term Glycemic Load, this refers to GI times the amount of food you eat. GI is like density, GL is like mass.) The higher the GI, typically, the higher your insulin goes up, then crashes. (There is more nuance here ( 7) and, as a scientist, I think I’m ethically obligated to apologize to Eran Segal, but let’s not go down a rabbit hole.)

This spike and drop in insulin, referred to as the insulin roller-coaster, causes “hormonal hunger.” Basically, your body isn’t really hungry for nutrients, which is “nutritional hunger.” Instead, you’re being deceived by fluctuation in hormones. In fact, it’s even been observed that changing the GI contents of a meal, without changing the meal’s taste, calories, or macronutrients, impacts the insulin roller-coaster and this alters activity in the brain’s reward center, the nucleus accumbens (the same region that lights up in response to cocaine), to trick people into “hormonal hunger” ( 8).

So, check out the GIs of your favorite foods and make smart choices. For reference, a carbless egg has a GI of 0, broccoli is about 15, watermelon is 72, and pure sugar is 100.

Let’s do like a sushi chef and wrap it up. Here are the key takeaways…

Counting calories is like trying to pogo-stick a marathon, it might seem like it’s working at the beginning but will probably fail long-term. Here’s what to know about counting calories.

Take Home Message

Calories in food are measured by bomb calorimetry, which doesn’t apply well to human biology because our cells use a very different process to extract energy.

We all have different microbiomes, which uniquely influence how we extract energy from food.

The law allows for a 20% margin of error on nutrition labels.

Exercise contributes to a small proportion of calories burned. Far more energy is burned by temperature regulation, fueling your brain, digestion itself.

NEAT refers to non-exercise related calorie burning activities, like bouncing your leg. Variations in NEAT account for a large variation among humans in calories burned.

Hormones govern how your body uses and distributes energy over the long term.

For the above reasons, you can’t accurately measure “calories in” or “calories out.”

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Nicholas Norwitz
MD-PhD candidate at Oxford University

Nicholas Notwitz

Nicholas Norwitz is a Harvard medical student and Oxford PhD researcher who specializes in ketone metabolism. He a rising star in the scientific community, with peer-reviewed publications on topics ranging from brain health to bone health to heart health to gut health.

Informed by his own medical history, he has an infectious passion for food as medicine and a drive to find innovative ways to teach the general public about the latest nutrition science.

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Comments (12)

Dear Nick,
You mentioned that differences in Microbiome can influence calories in. Do you know if the Microbiome changes when you change your intake to adjust for caloric restriction?
Sincerely,
Greg  

Reply

Yep! check you this blog: How Yo-Yo Diets Damage Metabolism and What to Do About It
And this paper: https://genie.weizmann.ac.il/pubs/2016-christoph-nature-november.pdf
Basically, the answer is yes. When you cut calories, your microbiome shifts to become more thrifty or obesogenic.
It also works in the reverse direction. Not that I'm saying you'll get a six-pack just from upping your intake, but I've found in myself and others that my maintenance threshold has slowly crept up as I've been ketogenic. I assume this is microbiome related, as my fasting BMR hasn't changed much. Over the first 18 months of being in full ketosis my maintenance intake increased by ~ +650 Calories. It was a steady, not a sharp, increase. That's just an n = 1, but for what it's worth. Anyway, check out the blog and paper because there is evidence that your microbiome adapts to caloric restriction. Sorry, I don't make Mother Nature's Rules, I just communicate them. Call me Hermes.

Reply

Hey Nick, great article! I actually follow you on Twitter and love LOVE your facts of the day!
My question is actually about counting calories when weight gain is the goal. I’m trying to put on some muscle mass because my lean mass is in the 7th percentile.
Is it important for my to count calories to get enough? I don’t have a huge appetite naturally. If not, do you have any advice on gaining weight in a healthy way?
Thanks 😊 - Marsha

Reply

Great Question! Admittedly, this blog was written with the majority in mind, i.e. those who want to lose weight. But maybe I should have included a caveat on hard gainers because, for people like you who want to healthily put on weight, counting calories (if an inexact science) can be necessary. Your body does need enough energy so you probably have some sort of rough caloric threshold. If your goal is to gain weight, then it's fine for you to overshoot this threshold and by precisely how much isn't really the object. But beyond meeting your personal threshold, my opinion is simply trying to pack calories on top of that isn't ideal because it becomes a big chore and, for many, isn't sustainable. I myself have tried that approach and there comes a point (judging from my own experience) where you just can't keep up the intake. My suggestions for alternatives to just smashing calories are as follows and all center on stimulating insulin & mTOR growth pathways:
(i) Eat more frequently. I still think it's healthy to say in a 12 hour window, but maybe do three meals a day if you're doing two or one. If you're doing three, you can probably stay there.
(ii) Post workout, combine carbs and protein and fat. The combination of macronutrients stimulates and insulin spike while there is energy available, as well as building blocks, for muscle. You don't actually need to do this post-workout, but I like to do so when trying to gain because it helps target the carbs to the muscles (keeping me in ketosis provided my net carbs stay below 35 grams). And, if you really want to capitalize on hormones for lean gain, do a fasted workout then have a large breakfast. This will let you get the advantages of both growth hormones and insulin spikes.
(iii) Try using Whey protein and BCAAs. Whey and BCAAs stimulate insulin/mTOR more than other protein sources. This will help your body with it's "get bigger" signal.
(iv) It never hurts to get more "energy." Therefore, instead of counting calories, try turning your "high-energy" fat sources into hyperpalatible forms. For example, instead of drenching things in oil (which becomes unpalatable) try making a tasty jar of mayo! Martina has a great recipe. Personally, I can triple my oil intake when it's in mayo form. Maybe the science isn't exact, but there is an anergy difference between a third and a full cup of oil/fat. You can also try one of Martina's awesome fat bombs!
(v) Of course, lift heavy and rest. Your body isn't going to grow muscle if you don't stimulate it to do so. Lift heavy, you may want to down the cardio, if you do cardio, and make sure to rest/sleep as much as your body tolerates.
Hope that helps you on your mission!
Best,
Nick

Reply

THANK YOU! This is super helpful and I’m definitely going to work with this.
Martina, do you think you’d ever do a high-calorie filter for KetoDiet recipes? I would guess maybe not since most people aren’t looking for that.
Thanks 🙏🏻

Reply

Hi Marsha, I'm sorry for the delayed response, we've been working on some pretty amazing app features (as a matter of fact it has to do with filtering!) and I realised I didn't get back to you We currently have an option to see all OMAD/TMAD meals although most of them are TMAD. You can find the meals here: ketodietapp.com/Blog/Filter
We will also add these into the app and the blog filter under Recipes to make it easy to find 😊

Reply

This is interesting... Unless I go below 1,200 I can't lose weight! I've been dieting for my whole life, tried almost every diet there is and nothing worked long term. I worry that if I eat more it will pile up again. My question is... if I go strict keto and eat more than I do now, can I still lose weight? Thank you!

Reply

Dear Jenna, thanks for your question. First, I would suggest you read my response to Hellen, who asked a related question. Assuming you're not a little person, then dropping below 1,200 Calories per day on average usually is associated with a slowed metabolic rate. You can get actual BMR testing to evaluate this, or, for an easier option, go to a BMR calculator and put in your age, sex, and weight. The calculator will spit out a number that is an approximate of how much energy your body should burn at complete rest. Since basic daily living and digesting food alone will burn hundreds of kilocalories, if your intake is even close to this number, you're probably under-eating eating and your body is adjusting your metabolism to compensate. Here is one such calculator: https://www.active.com/fitness/calculators/bmr. You can also select the caloric needs button and put in your level of activity if you feel that would be informative to you.
There are a few reasons I would caution you about eating substantially less than you require (outside the margin of error above). The first, and the one that might peak your attention the most), is the caloric restriction long-term can lead to metabolic and microbiome changes that actually lead to long-term weight gain. For example, when you cut energy intake too low, your thyroid hormone can drop, your NEAT will go down, and your microbiome can shift to become more thrifty AND your hunger hormones change driving your to eat your "needs" over the long term (even if you think you aren't people are great at deceiving themselves). Thus, you've shifted your metabolism to becoming better at storing calories and when you YoYo back to baseline (inevitably, sorry, it's not you it's biology) the weight piles on. Worst part, this happens faster every time you YoYo! See my blog on YoYo diets here for more: How Yo-Yo Diets Damage Metabolism and What to Do About It.
Another thing worth mentioning is that when you restrict intake and force you body to choose how to allocate energy, it's going to cut "funding" from the long-term processes that aren't essential to immediate survival. This means, your bones might start to breakdown and your reproductive function may begin to fail. There is actually a name for this condition: Relative Energy Deprivation Syndrome, and it's associated with cognitive changes, osteoporosis, and loss of menses.
Now, you asked if you will gain weight if you eat more calories and go Keto. No, I don't think so. Try this: eat 50 more kilocalories per day each week and decreased your carbs by 10% each week. So, if you start by eating 1200 kilocalories and 100 grams of carbs, week 1 would be 1250 Calories and 90 grams of net carbs. Keep doing this for a little while and see how you feel. I wouldn't weight yourself for at least 1 month as water weight can fluctuate. Do you want to try that and then check in in 1 month? Martina and I are always happy to be a resource on your journey to health.

Reply

Nick I just wanted to say how much I appreciate your response. I don't see that often and I read a lot of blogs! I will do what you suggest and I can't wait to see what happens. I'm so excited to get started! I've been trapped in the same weight loss-weight gain cycle for way too long and I know I can't keep going like that. The option is either to face the fact that I won't be able to lose weight or try something else to address the root cause of this. Thank you so much, will report back!

Reply

Jenna, it's my pleasure. The reason Martina makes her livelihood on low-carb high-fat, and the reason I'm doing an MD PhD on the topic and devoting my life to it, is because we've both experienced its life-changing impact on health personally. She cured thyroid disease. I've resolved my ulcerative colitis, osteoporosis, and given myself a better chance of long life without Alzheimer's despite being AopE4/4. For both of us, it's personally and we can empathize with that hopeless feeling one can feel when they feel like they've tried everything and put every effort forward and nothing has helped. You have a community of support if you look for it and I promise you there isn't a person in the world who literally can't achieve a healthy weight. A few are unlucky enough to have serious medical problems like Cushings disease that require medical interventions, but for most it's just an issue of poor information and misdirection. First step for you sounds like improving your metabolism. Then you can move forward to optimize body composition in a healthy way. You can be lean, high energy, and metabolically healthy. It's in your future! Just need the right information and support!

Reply

Thank you Nicholas! I had no idea about any of this. I love the idea of meal golf. I think I may trade calorie for that and see how it goes.
Question, is there a way to figure out if I’ve damaged my metabolism from counting calories and possibly restricting calories a little bit?

Reply

Yes, indeed there is a way, or ways. The best thing to do is to get a basal metabolic rate (BMR) respiratory test. Basically, you lay down for 15-30 minutes while a machine measures the gases you exhale. Your exhalations give insight into your cellular respiration and tell you how many calories per day you burn at complete rest. If this number is a lot lower than calculations based on you weight, age, and sex predict it suggests you’re “metabolically damaged.”
Another thing you can do is get a thyroid panel, including free and total T3 measures (these are often excluded but the most important). If your T3 levels are low that can also suggest metabolic adjustments to save calories. A caveat to this is that T3 can actually decrease with weight loss from cutting carbs BUT specially in that instance your basal metabolic rate doesn’t appear to decrease but of improved thyroid hormone sensitivity. That is, at least, the prevailing thought.
But let me be clear that metabolic damage/adjustments from caloric restriction aren’t necessarily bad for your long term health nor are they irreversible. To recover if you are “adjusted,” I’d suggested slowly bringing your calories per day up (ironic I know, but for this you may want to track; call me a hypocrite but more of the same foods is more energy) bringing your carbs down at the same time.  
Good luck!

Reply