What is a Calorie?
The amount of energy needed to raise the temperature of a gram of water by 1 degree Celsius at a pressure of 1 atmosphere.
Caloric Content of Macronutrients:
Proteins 4 kcals/g Carbohydrates 4kcals/g Fats 9kcals/g
Energy Balance:
The symmetry between nutrient consumption and energy demands of the body
Negative Energy Balance:
More energy expended than consumed
Positive Energy Balance:
More energy is consumed than expended
In theory, we can look at the energy intake in a 24-hour time frame and conclude that excess calories (energy) result in weight gain whereas deficiency of calories results in weight loss.
However, realistically, when counting calories, we're not accurate. We must identify various factors to fully utilize the principle of caloric balance.
These factors include the physiology of calories out, how fiber affects metabolizable energy, and the accuracy of tracking food.
Physiology of Calories Out
The total daily energy expenditure refers to the summation of all energy spent in a day.
So how is this energy summed up?
Resting Metabolic Rate (RMR)
is the energy expended through metabolic and physical processes when the body is at rest. This accounts for about 60-75% of total daily energy expenditure. (1)
What can you do to use more energy at rest?
RMR is correlated with your weight, height, gender, and age. The only correlation you can modify is your weight.
To achieve an increase in your RMR, you can increase your muscle mass or fat, thus, needing more energy to power the use of the extra weight.
With the loss of adipose tissue, the RMR decreases, which is why focusing on increasing muscle mass through strength or hypertrophy training is essential whilst losing body fat to maintain your RMR(2).
Thermic Effect of Food or Diet Induced Thermogenesis
refers to the energy expended to extract energy from food which accounts for about 5-15% of total daily energy expenditure. In fact, all sources of calories have a differential effect on energy expenditure.
The energy expended to extract energy from protein is around 15-30%, followed by carbohydrates at 5-10% and fats at around 0-3%(3).
FOOD COMPOSITION | ENERGY EXPENDED TO EXTRACT ENERGY |
100 kcals FROM PROTEINS | 15-30 kcals |
100 kcals FROM CARBOHYDRATES | 5-10 kcals |
100 kcals FROM FAT | 0-3 kcals |
Are you taking into account the difference in energy expended to extract the energy from the macronutrient composition of your diet when counting your calories?
Of course not!
However, there are advantages to allocating your macronutrient intake in accordance with your goals.
Solely looking at the thermic effect of food, If your goal is to lose weight, we recommend a diet high in protein. On the other hand, if you want to bulk, then getting enough protein, about 1.0-1.6g of protein per kg bodyweight per day(4), and filling your macronutrients with more fats and carbohydrates would better utilize the TEF.
Physical Activity-Induced Energy Expenditure
refers to both the amount of energy expended through voluntary exercise and the energy expended unconsciously through daily living (NEAT). This accounts for about “15% in a very sedentary person to 50% in a highly active subject”(5).
Thus, if you work a sedentary job, take advantage of the conscious exercises you can execute to use more energy. Be a highly active subject instead of a sedentary person!
Can you accurately count how many calories you lose during voluntary exercise?
Unfortunately, calorie-tracking wearable devices and workout machines are overestimations of how much energy you expend.
A systematic review of 158 publications examined 9 different commercial wearable device brands, in regard to energy expenditure, no brand was accurate(6).
Similarly, a study used healthy adult volunteers who performed exercise protocols in a controlled laboratory setting which were assessed to examine the accuracy of 7 available wrist worn devices in estimating heart rate and energy expenditure. With an error rate of 5% to be within the acceptable threshold, the error in energy expenditure was significantly higher than heart rate for all devices. Median error rates varied from 27.4 to 92.6% which shows that no wrist worn monitoring device reports energy expenditure within an acceptable error range(8). This is why a review of 27 studies revealed that future research needs to adopt a minimum reporting threshold of data generated by wearable activity trackers to increase feasibility(7) as each device uses its own proprietary algorithm to calculate energy expenditure.
Furthermore, exercise machines do not account for various variables like skill level(easier to execute than others), body composition(efficiency of burning calories), executing the exercise without assistance (leaning your arms against the handrail), the resistance changing over time(rust and tear), and the way athletes use them(some machines offer more freedom of movement than others).
The formula exercise machines use is generally based on the compendium of physical activity which contains 821 codes for specific activities to identify the rate of energy expenditure through the metabolic equivalent of task(MET) concept. This is defined by the amount of oxygen consumed while sitting at rest expressing the energy cost of physical activities as a multiple of the resting metabolic rate(9). This unfortunately does not account for factors related to individual differences and is quite inaccurate when measuring calories expended.
Ultimately, use an error rate of at least 20%. Hence, if your wearable device or workout machine states that you have expended 500 kcals, estimate that you burned about 400 kcals.
Non-exercise Activity Thermogenesis (NEAT)
is the energy expended unconsciously through daily living and includes fidgeting, walking, standing, spontaneous contractions of muscles, chewing, playing an instrument, singing, dancing, and/or tapping of the feet.
To emphasize the significance of NEAT in relation to weight management, a study with 16 lean volunteers were overfed by 1000 calories per day above weight maintenance needs, those who increased their NEAT the most did not gain fat, even when overfed. Their bodies also adjusted accordingly in relation to increasing unconscious energy output through NEAT due to the body spontaneously increasing physical activity unconsciously(10).
Most of the variances in individuals regarding NEAT are generally associated with differences in occupation. Analyzing the lifestyle based prediction model of physical activity levels by dividing total daily energy expenditure(TDEE) by the basal metabolic rate illustrates the differences in activity levels with various occupations(11).
OCCUPATION TYPE | PHYSICAL ACTIVITY LEVEL |
CHAIR BOUND OR BED BOUND | 1.2 |
SEATED WORK WITH NO OPTION TO MOVE, LITTLE TO NO STRENUOUS ACTIVITY | 1.4-1.5 |
SEATED WORK WITH DISCRETION AND REQUIREMENT TO MOVE, LITTLE TO NO STRENUOUS ACTIVITY | 1.6-1.7 |
STANDING WORK | 1.8-1.9 |
STANDING WORK OR HIGHLY ACTIVE LEISURE | 2.0-2.4 |
This table shows the lifestyle-based prediction of physical activity level values(11).
When counting calories, are you considering how much energy you are expending through NEAT?
You can get an estimation of calories burned based on the activity through various tools like the lifestyle prediction model, energy expenditure of unconscious physical activity above rest, and websites like MyFitnessPal.
Although inaccurate, If a sedentary individual increases NEAT by creating lifestyle changes to include more unconscious movements, energy expenditure through NEAT can increase as much as 2000kcals(11)!
Is this a genetic trait or something we can all take advantage of?
Although, higher NEAT may occur in lean individuals through a genetic predisposition influencing the phenotypic development of more unconscious movements. We can still manipulate how much energy we use unconsciously by walking, standing instead of sitting, singing while driving, fidgeting, using stairs instead of an escalator, creating accountability tasks, or even chewing gum!
This figure depicts the energy expenditure above rest for various activities(11).
Thus, we can all take advantage of NEAT!
Next, we need to consider the two types of dietary fiber in relation to how they affect metabolizable energy.
What is fiber?
Fiber
is a type of complex carbohydrate that is mostly indigestible but plays an important part in the diet. There are two types of dietary fiber found along digestible simple and complex carbohydrates in plant foods like fruits, grains, legumes, nuts, seeds, and vegetables.
Soluble Fiber
dissolves in fluids in the stomach and is broken down in the large intestine, providing about 2 kilocalories per gram. It slows the rate at which nutrients are digested and absorbed into the bloodstream.
Insoluble Fiber
does not dissolve in water and is intact through the gastrointestinal tract, speeding up food and waste through the digestive system. This type of fiber contributes to the majority of stool formation; therefore, it is not a source of calories.
How does fiber affect the metabolizable energy of the food that we eat?
Presumably, the metabolizable energy value depends on the type of dietary fiber as well as the overall composition of an individual’s diet.
When looking solely at total dietary fiber, a study found that overall, increasing fiber intake decreased fat and protein digestibility. Therefore, the metabolizable energy content of the diets decreased as fiber intake increased. However, when subjects consumed low-fat diets, there was no effect of fiber intake on fat digestibility(12).
Moreover, a statistical analysis of 43 different human diets with 1.9–93.1 grams per day of dietary fiber from various sources determined a generalized linear regression of the relationship between the availability of digestible energy and the intakes of dietary fiber or unavailable complex carbohydrates(13).
Therefore, the decrease in metabolizable energy density is associated with the limited energy availability from fiber carbohydrates and the inhibitory effect of fiber on fat and protein digestibility. Nutrient interactions and the associated inaccuracy of predicting the metabolizable energy content of diets may contribute to food labeling inaccuracies resulting in potential deleterious consequences for consumers(12).
Can you accurately count calories in?
In order to evaluate the accuracy of nutrition label information in accordance with a standard for compliance, the FDA regulations define two classes of nutrients and a third group.
Class 1 nutrients involve fortified or fabricated foods like vitamins, minerals, dietary fiber, protein, or potassium that are added to foods. These nutrients must be present at 100% or more of the value shown on the label(15).
Comparatively class 2 nutrients comprise vitamins, minerals, protein, total carbohydrates, dietary fiber, potassium, and polyunsaturated and monounsaturated fats that occur naturally in food. These nutrients must be present at 80% or more of the value declared on the label to be compliant with regulations(15).
The third group of nutrients includes calories, sugars, total fat, saturated fat, cholesterol, and sodium. The label is considered out of compliance if the nutrient content is greater than 20% above the value indicated on the label(15).
A research paper also measured the energy values of 29 quick-serve and sit-down restaurant foods and 10 frozen meals purchased from supermarkets. The restaurant food averaged 18% more than stated values, as the frozen food averaged 8% more than originally stated(14)
How do you utilize calories in?
A whole food, unprocessed, nutrient-dense diet is a helpful strategy to avoid the caloric errors in many processed foods labeling. Also, focus on the ingredients when purchasing food to be more mindful of what you are putting into your body. Being more mindful and consistent with what you are intaking will eventually result in a better understanding of what you are really ingesting and strategies to manage calories in.
Typically, weighing in first thing in the morning after using the toilet, and averaging the weight weekly and the physical depiction of your physique will help with consistently understanding if you are in a caloric deficit, surplus, or maintenance. Therefore, it is best to use these tools as estimations with at least 20% room for error.
Therefore...
In theory, the calories in - calories out principle is valid, yet, we must consider the physiology of calories out, fiber intake in relation to metabolizable energy, and the accuracy of tracking calories to better utilize this principle.
Ask yourself, when counting calories:
Do you consider how many calories you burn at rest?
Do you anticipate the number of calories lost through NEAT?
Do you consider the Thermic Effect of Food?
When voluntarily exercising, are you noticing the overestimation of calories burned on exercise machines or from your wearable device? Are you carefully adding the +/- amount of error?
Do you look at the fiber content of each food and distinguish whether it will affect the overall caloric content of the food you intake?
Do the foods you purchase accurately depict the calorie content?
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References
(1) Poehlman, E T. “A review: exercise and its influence on resting energy metabolism in man.” Medicine and science in sports and exercise vol. 21,5 (1989): 515-25. [PubMed]
(2) Stiegler, Petra, and Adam Cunliffe. “The role of diet and exercise for the maintenance of fat-free mass and resting metabolic rate during weight loss.” Sports medicine (Auckland, N.Z.) vol. 36,3 (2006): 239-62. doi:10.2165/00007256-200636030-00005. [PubMed]
(3) Pesta, Dominik H, and Varman T Samuel. “A high-protein diet for reducing body fat: mechanisms and possible caveats.” Nutrition & metabolism vol. 11,1 53. 19 Nov. (2014): doi:10.1186/1743-7075-11-53 [PubMed]
(4) Wu, Guoyao. “Dietary protein intake and human health.” Food & function vol. 7,3 (2016): 1251-65. doi:10.1039/c5fo01530h. [PubMed]
(5) Parmar, Rasik M. and Ahmet S. Can. “Physiology, Appetite And Weight Regulation.” StatPearls, StatPearls Publishing, 29 August 2022. [PubMed]
(6) Fuller D, Colwell E, Low J, Orychock K, Tobin MA, Simango B, Buote R, Van Heerden D, Luan H, Cullen K, Slade L, Taylor Nga. "Reliability and Validity of Commercially Available Wearable Devices for Measuring Steps, Energy Expenditure, and Heart Rate: Systematic Review". JMIR Publications Vol 8, 9 (2020): doi: 10.2196/18694. [Link]
(7) Chan, Alexandre et al. “Reporting adherence, validity and physical activity measures of wearable activity trackers in medical research: A systematic review.” International journal of medical informatics vol. 160 (2022): 104696. doi:10.1016/j.ijmedinf.2022.104696. [PubMed]
(8) Shcherbina, Anna et al. “Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort.” Journal of personalized medicine vol. 7,2 3. 24 May. 2017, doi:10.3390/jpm7020003. [PubMed]
(9) Ainsworth, Barbara E et al. “2011 Compendium of Physical Activities: a second update of codes and MET values.” Medicine and science in sports and exercise vol. 43,8 (2011): 1575-81. doi:10.1249/MSS.0b013e31821ece12. [PubMed]
(10) Levine, James A. "The 'NEAT Defect" in human obesity: The Role of Nonexercise Activity Thermogenesis." Endocrinology Update, vol.2,no.1, 2007, pp.2-3, https://www.mayoclinic.org/documents/mc5810-0307-pdf/doc-20079082. [Link]
(11) Levine, James A, et al. "Non-Exercise Activiy Thermogenesis: The Crouching Tiger Hidden Dragon of Societal Weight Gain." Arteriosclerosis, Thrombosis, and Vascular Biology vol.26 (2006): 729-736. [Link]
(12) Baer, D J et al. “Dietary fiber decreases the metabolizable energy content and nutrient digestibility of mixed diets fed to humans.” The Journal of nutrition vol. 127,4 (1997): 579-86. doi:10.1093/jn/127.4.579. [PubMed]
(13) Livesey, G. “Calculating the energy values of foods: towards new empirical formulae based on diets with varied intakes of unavailable complex carbohydrates.” The European journal of clinical nutrition vol. 45,1 (1991): 1-12. [Link]
(14) Lorien, Urban E, et al. "The accuracy of stated energy contents of reduced-energy, commercially prepared foods." Journal of the American Dietetic Association vol. 110, 1 (2010): 116-123. [Link]
(15) U.S. Food and Drug Administration. FDA. https://www.fda.gov/. Accessed 17 Feb. 2023. [Link]
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