Column by Gavin Guard: Do Calories Matter? Featured

Within the last few years, I have witnessed a lot of confusion over what calories are and if they in fact matter or not when it comes to weight loss and health. Do calories have a role in dictating successful weight loss or is it another antiquated piece of advice from ill-informed food organizations?

Some individuals like Gary Taubes in his book, “Good Calories, Bad Calories” have purported that calories do not matter at all. He and others make the case that it is in fact carbohydrates and the insulin response from the intake of these carbohydrates that cause us to be fat. They point to weak anecdotal evidence and mechanistic data to support their claims. I believe they have missed the broader picture of how our body processes the food we eat. This has only muddied the water when it comes to the question, of “what can I eat to be healthy?”

Here, I’d like to summarize the notion of calories- what are they and do they matter? As we all may know, food contains energy. This energy found in food has historically and conveniently been measured in calories (which is the energy required to heat up 1 gram of water by 1 degree Celsius).

This brings us to the notion of the First Law of Thermodynamics which is a well-established scientific observation that energy is neither created nor destroyed but rather transferred from one form to another. When we replace the word “energy” with the word “calories” (since calories are a form of energy), we get “calories are neither created nor destroyed”. This means that we cannot just eat a box of donuts every day and magically not gain any weight- the calories found in the donuts need to go somewhere (in this case, fat). When more calories are provided to the body than it can handle or needs to perform processes such as breathe, walk, and exercise, then the body will store this energy in the form of muscle or fat (as well as other storage forms).

We have established that the food we eat contains calories (a measurement of energy) and these calories need to be partitioned by the body to perform both subconscious and intentional work. Part of the consumed calories goes toward our basal metabolic rate which includes maintaining our core temperature and fuel basic processes by our organs such as our brain, heart, and liver (this accounts for about 70% of our calorie expenditure). Another portion of calories goes toward intentional exercising (5-10% of calorie expenditure) while even more calories go toward something called non-activity exercise which includes walking the dog, talking, standing, doing the dishes, sweeping the floor, etc. (15-50% calorie expenditure). Finally, a portion of the calories found in food goes toward breaking down, digesting, and transporting the food to our cells (ironic, I know). This is called the “thermic effect of food” and accounts for 15-20% of calorie expenditure.

We can influence much of how and to what extent our body partitions the calories we get from our food through various diet and lifestyle interventions which I may expand on in a latter post.

It’s important to note that this equation is not static, meaning, the first part of the equation (calorie intake) affects the latter part of the equation (calorie expenditure) and vice versa.

Anecdotally, I have plenty of examples to show this in action. For example, increased calorie expenditure through increased amounts of exercise will inevitably lead to the brain’s subconscious effort to increase calorie intake by eating more food. This is why the notion of just “eat less and move more” is a very ill-informed piece of advice to give someone.

On the flip side of things, I have also observed through experience and research how reducing food intake will spontaneously reduce energy expenditure via reducing non-exercise activity. You see this to the extreme with dieting bodybuilders who walk slower, talk slower, and seem pretty lazy outside the gym environment. Their brain is trying it’s best to preserve fat and muscle tissue by dramatically attenuating energy expenditure.

Let’s wrap this up with some take home points. First, I want to highlight the fact that calories do matter, and this aligns with the basic laws of physics. Weight loss comes from the successful adherence to an energy deficit (spending more calories than you eat). This is quite nuanced and difficult in the long-term but can be done with the correct approach.

Second, we can both influence the “energy in” portion and the “energy out” portion of the energy equation by various diet and lifestyle factors. Such interventions include altering food quality, creating some level of cognitive oversight over our activity levels, and optimizing hormone levels just to name a few.

I hope this was helpful in helping you gain a better understanding of the complex field of nutrition research. Please feel free to reach out with any comments or questions at 

Gavin will soon be graduating from the University of Colorado as a PA. He also is a certified nutritionist and has additional professional functional medicine training. He is the medical director at Roots Health Community which focuses on managing and reversing chronic illnesses through a functional medicine approach. Roots’ mission is to dramatically transform the health of the island community and create a world-class patient experience. If you would like to become a patient at the clinic, you can reach out to Gavin at Roots Health Community will be opening in the fall of 2020.  

Gavin, Lindsey and their daughter Ellie will be familiar to most islanders.


  • Margaret
    Margaret Sunday, 09 February 2020 21:17 Comment Link

    Calories definitely matter a lot especially when you looking for weight loss. I like the way you wrap this article in a short post. Can you please mention some eatables which contain high calories? looking for your response.Thanks

  • Gavin Guard
    Gavin Guard Thursday, 06 February 2020 04:47 Comment Link

    Hi Stefan,

    Thank you for your thoughtful reply. To reiterate my point, calories do matter but so does metabolism on the energy out side of the equation. Certainly, the macronutrient and the micronutrient composition of the diet has a huge impact on health. My intention of this piece was to push back on the notion that calories don't matter at all and that it is all about carbohydrates. Your point on twins is intriguing- you bring up the notion of epigenetics and the potential for other parts of the individual's environment to dictate their health (and weight). Please cite evidence that the high-carb eater will gain weight as this is something that sounds familiar from guys like Gary Taubes. I will link peer-reviewed research here of studies looking at this question of if carbs make us fat- it does not seem to be the case that they do. Most meta-analysis show that low carb diet may give us a few more pounds of weight loss after a year or so but this is by no means clinically significant and is mostly driven by a loss of glycogen. However, I think a low-carb diet can and will work for a subset of the population.

    Low Carbohydrate versus Isoenergetic Balanced Diets for Reducing Weight and Cardiovascular Risk: A Systematic Review and Meta-Analysis by Naude et al 2014

    Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women; The A TO Z Weight Loss Study: A Randomized Trial by Gardner et al 2007

    Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion The DIETFITS Randomized Clinical Trial by Gardner et al 2018- this study was recently published in JAMA

    Review of current evidence and clinical recommendations on the effects of low-carbohydrate and very-low-carbohydrate (including ketogenic) diets for the management of body weight and other cardiometabolic risk factors: A scientific statement from the National Lipid Association Nutrition and Lifestyle Task Force by Kirkpatrick et al 2019

  • Ciely Gray
    Ciely Gray Wednesday, 05 February 2020 10:51 Comment Link

    Great article! Love hearing you are trained in Functional Medicine.
    I lead a Keto group here on San Juan Island and would love to connect.

  • Stefan
    Stefan Wednesday, 05 February 2020 10:50 Comment Link

    I don't find this article very convincing. I do not question the validity of the First Law of Thermodynamics, but it alone does not provide sufficient insight into the matter of weight gain/loss. Since the author las led us into the domain of physics, I would ask him to consider the following physics-style thought experiment: identical twins with identical lifestyles, consuming an equal amount of calories: one in the form of fats and proteins, the other, carbohydrates. Over time, the carb-eater will be fatter. So calories alone are not the answer. Metabolism matters. For example, if the body cannot store fat because insulin pathways are blocked somehow, there will be less weight gain, even if many calories are consumed.

    I don't think what I wrote above is terribly controversial. It is certainly not new. But now I will up the ante. I myself am a retired elementary particle physicist and, in my view, the same misleading arguments are made by climate change alarmists. In their simplistic analysis (again based on the First Law) if CO2 absorbs infrared energy that originally came from the Sun at a much higher frequency, then the Earth must get warmer. It's simply not true. You have to look at the Earth's "metabolism", i.e., the many complex mechanisms (some of them poorly understood) through which energy flows occur. An example is cloud formation in the atmosphere. As a result, global temperatures can be relatively stable even as CO2 concentrations rise and the greenhouse effect is in full force.

    One more thing. The mistake that health professionals and climate activists often make is to limit their thinking to the dynamics of the human body or the Earth. A much better way to look at these systems is to consider them as quasi-static. At any given time, a human being is at a certain weight, and the Earth at a certain temperature. Yes, these can change, but they do so very slowly. The relevant values (weight, temperature) are a result of complex, fairly stable internal processes, not so much short-term energy imbalances. All this while the First Law reigns supreme.


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