What is A Calorie?

“The Institute of Medicine recommends a range of 10% to 35% of daily calories come from protein with the deciding factor being an individual’s total daily energy expenditure.”

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What Does It Mean?

When people hear the word “diet,” it is common for them to assume the definition revolves around the restriction of certain foods and drinks in hopes of losing weight. While this is partially correct, dieting is merely eating in a controlled fashion to aid in a particular outcome. These outcomes range from weight loss, weight gain, or weight maintenance, to a host of medically relevant goals such as reducing cholesterol levels or lowering blood pressure. Although dieting (concerning the amount of food needed) is subjective to the individual and their goals, there are a few universal consequences that stem from eating in a caloric deficit, a caloric surplus, and even at a caloric maintenance. I think it is fair to say that the average American is aware that the FDA has a recommended daily caloric intake for adult men and women. I also think it is fair to say that the average American has no idea what a calorie is. Lets clear that up. In laymen terms, a calorie is a unit of energy. In science, the definition does get broader. In 1842, the definition of a calorie (cal) was published in a science-based journal called “Le Producteur,” thanks to the work of a man named Nicolas Clément. Clément defined a calorie as the amount of energy required to heat up one gram of water by one degree Celsius. Eventually, measurement systems become more efficient, and we all settled on the kilocalorie (kcal) as the universal measurement for food. A kilocalorie, dubbed the food calorie, is the mathematical equivalent of one thousand Clément calories. The critical thing to take away here is the fact that a calorie is a measurement of energy and nothing else. This means that the body is merely a function of the first law of thermodynamics, also known as the law of conservation of energy. The law of conservation of energy states that energy cannot be created nor destroyed, it can only be transferred from one form to another. The implications are straightforward, if you consume 2,000kcals worth of food per day, you will need to burn 2,000kcals (via putting your body in motion) to offset your caloric intake. If you succeed, your weight will remain virtually stagnant (outside of daily fluctuations caused by water intake, sodium intake, etc.). If you fail, you’ve entered a caloric surplus. A caloric surplus leads to weight gain due to your body storing excess energy. Likewise, if you consume 2,000kcals worth of food in a day but burn 2,500kcals, you’ve entered a caloric deficit. A caloric deficit forces your body to use previously stored energy for fuel and ultimately results in weight loss. Whether you’re looking to gain, lose, or maintain weight, calories in versus calories out will dictate that process.


Carbohydrates, better known as carbs, also known (wrongfully so) as the devil, can be defined as sugars, starches, and fibers that enter the body and break down into glucose. Carbs are abundant in fruits, vegetables, and grain-based foods like bread, cereal, and pasta. Carbs are also one of the three essential macronutrients and serve as the body’s primary source of energy. They fuel the central nervous system, the muscular system, and even the brain. For those wanting to preserve or build muscle mass, carbs also protect our bodies from burning protein as an energy source. Popular weight loss diets are usually based on decreasing or even eliminating carb intake. Unfortunately, this has led to the common misconception that carbs are bad for you. Although people do tend to lose weight on a low carb diet, it is important to remember that correlation does not equal causation. A large percentage of carb based foods are calorically dense. When you remove a calorically dense group of food from your diet, you’re more than likely going to ingest fewer calories leading to a faster rate of weight loss. A reduction in caloric intake is the culprit, not a reduction in carb intake. To further that point, just because a macronutrient has a higher potential for over ingestion does not inherently make it unhealthy. That is not how science works. American culture puts carbs on top of carbs for nearly every meal. Syrup on top of pancakes, jelly on top of bread, and milk to complete our cereal. Culturally abusing the nutrient doesn’t change it’s value, purpose, or function within our body. With that said, some carbs do act differently in the body than other carbs. Carbohydrates can be broken down into two categories, simple carbs, and complex carbs. Monosaccharides (single sugar carbs) and disaccharides (two sugar carbs) are classified as simple carbs. Simple carbs are easier digested and have a higher absorption rate than complex carbs. A few examples of simple carbs include milk, yogurt, table sugar, honey, and refined sugar. A carb that is easily digested does not suggest it is healthy. Simple carbs can be heavy in refined sugar and contain little to no micronutrients (vitamins and minerals). On the other hand, complex carbs, also known as polysaccharides, are defined as carbs with three or more sugars. Complex carbs include green vegetables, starchy vegetables, peas, beans, pasta, corn, and even soymilk. Because carbs break down into glucose when they enter your body, their digestion rate controls how they affect your blood sugar. Simple carbs cause a spike in blood sugar, providing you with the classic “sugar high.” Complex carbs tend to give a more extended, steadier, and more evenly distributed type of energy that would be beneficial throughout something like a long day at work. Whatever glucose is not used for energy is converted to glycogen and stored in the skeletal muscles as well as the liver. When glycogen storage has reached its limit (somewhere around 2000kcals worth), your body transitions and stores carbs as fat. Again, you can see how the abuse of carbohydrates leads to a slippery road. With that said, carb intake is undoubtedly essential to human life, and although dieting for long periods of time without carbs is possible, we do not recommend it. 


Protein is perhaps the most understood of the three macronutrients due to its straightforward job in building and maintaining muscle mass. Protein, commonly found in animal products (but not restricted to animal products), is composed of a variety of combinations of 20 different amino acids. In the sports world, the two most common types of protein discussed are whey protein and casein protein. Whey protein is naturally found in milk and is produced via a process that involves liquid extraction, pasteurization, and drying the remains until it converts into a powder form. Whey contains all essential amino acids, digests faster than casein, and contains a higher concentration of leucine which is responsible for increasing muscle protein synthesis. It is common for supplement companies to spend their advertisement money on whey protein due to its association with building muscle mass. Much like whey, casein is another type of protein naturally found in milk. Although similar, the extraction process for casein protein is much simpler; extract the curds from curdled milk, and you have extracted casein. Casein also contains all essential amino acids but has a lower level of leucine and a long digestion period. When ingested, casein continues to curdle in your stomach. This process can be beneficial because it acts as a slow releasing agent, in other words, it keeps the protein in your bloodstream longer than whey. On top of that, casein contains a high amount of peptides that aid in the strength of your immune system, a high-fat content which supports absorption of micronutrients, and studies show casein minimizes protein break down which is good for muscle preservation. There is a bit of evidence that suggests protein consumption can also keep you feeling full for a longer period compared to eating food high in carbs or fat. In 2014, a study titled “Effects of High-protein vs. High- Fat Snacks on Appetite Control, Satiety, and Eating Initiation in Healthy Women” concluded that the subjects tended to eat less throughout the day after ingesting high protein snacks.  The amount of protein needed for an athlete on a day to day basis happens to be one of the most highly debated topics in fitness. Some people swear that you only need 0.8 grams of protein per kilogram of body weight. Others believe you need upwards of 2-2.5 grams of protein per kilogram of body weight. The fundamental issue with studies that support both claims is simple, the needs of the human body are dependent on outside forces and how those outside forces affect the body. If a 180lbs long-distance runner hops on a treadmill and knocks out a 2-mile run, their protein needs are going to be drastically different from a 180lb strength athlete completing the same workout. A good point of reference for protein intake is the total percentage of daily calories that come from protein. A sedentary person may function fine with 10%-15% of their daily calories coming from protein. An athlete that vigorously trains for their sport may benefit more if 30%-35% of their daily calories come from protein. The Institute of Medicine recommends a range of 10% to 35% of daily calories come from protein with the deciding factor being an individual’s total daily energy expenditure. There are a few studies that suggest overeating protein can lead to bad breath, kidney damage, and an increased chance of heart disease. Unfortunately, it is uncommon for a study that is based on protein intake to provide the participants with a source of protein that is low in fat. Red meat contains high amounts of saturated fat and cholesterol, thus making it difficult to pinpoint the reason for a change in bodily functions when examining the results from a study. Protein is everywhere, and there are multiple options when it comes to finding a source. We previously mentioned the two most supplemented versions of protein in whey and casein. Other options include hemp protein, soy protein, meat, poultry, beans, eggs, and even nuts and seeds. Thankfully for muscle building, it is easy to find a portion of food that has a moderate-to-heavy dose of protein per serving in each of the categories previously listed. Plant-based diets are becoming more popular with the rise of the internet and a rise of awareness of animal cruelty. Scientifically, the majority of plant-based proteins are not complete proteins. A complete protein contains the nine essential amino acids that our bodies cannot produce on their own. The essential amino acids are leucine, valine, histidine, isoleucine, phenylalanine, threonine, tryptophan, lysine, and methionine. Non-meat eaters will be very quick to tell you that combining different plant-based foods can provide your body with all nine essential amino acids and they are correct. Each plant, bean, and grain contain a different combination of amino acids so combining them can provide your body with a complete source or protein assuming that you’re aware of what you’re doing. Timing, frequency, amount, and the debate on sources set aside; protein is essential to everyday life. Eat it.


If protein is the most understood macronutrient of the bunch, dietary fat is the polar opposite, and then some. The truth is, very few people, professionals included, understand the ins and outs of dietary fat. It is the most loved, hated, and debated macronutrient of all. For the sake of everyone’s sanity, we will sidestep the debates and discuss the undeniable function that dietary fat serves in our bodies. Fat is fuel. We previously mentioned that carbohydrates serve as the bodies main source of energy, this remains true. But, we also learned that carb storage has a limit, as does the amount of time we spend using it as an energy source. Although carbs are the bodies main source of energy, fat is the bodies most abundant source of energy. After carb burning has reached its limit, the body switches to stored fat for energy consumption. This is where weight loss comes from. If you eat in a caloric deficit, your body composition changes due to the content of body fat decreasing from being used as an energy source. The function of fat doesn’t stop there, fat aids in the absorption of vitamins acts as an insulator for the body, protects vital organs, and aids in the health of the skin. Outside sources of essential fats, also known as fatty acids, contribute to brain development and inflammation control. Fats can be reduced down to three main categories; saturated fats, unsaturated fats, and trans fats. The difference between the three come down to their molecular structure and the number of hydrogen atoms connected to each structure. Unsaturated fat contains vacancies in its molecular structure that allow outside hydrogen atoms to bond. Saturated fats are packed with hydrogen, not allowing any space for external hydrogen atoms to bond. Trans fats are merely unsaturated fats that have been altered via the introduction of outside hydrogen in hopes of extending shelf life. In the midst of the current fat craze, I should also note that trans fats are naturally found in certain meats, just in minimal quantities. Expanding on the three categories allows us to look at fats in a more specific manner. Monounsaturated fat, a type of unsaturated fat, is one of the main components of avocados. Avocados are generally considered “healthy” and favoritism of monosaturated fat is the reason why. There appears to be evidence that monosaturated fats help control blood sugar, insulin levels, and even cholesterol levels. Polyunsaturated fat, also a type of unsaturated fat, is the primary fat found in plant sources and fatty fish. Polyunsaturated fats are favored due to their role in delivering essential fatty acids omega-3 and omega-6 to the body. From here, the conversation on fat gets too opinionated for my liking. Bad business practices and studies funded with money from those who have an agenda has resulted in a war on fat that has caused a blurred line between what’s healthy and what isn’t. The honest truth, the one most do not want to admit, is we are still in the process of understanding fat regarding what types, how much, and how often we should consume them. What we have done is identified that our body does have a threshold. We can, without doubt, say that a diet that includes no dietary fat is not an option. On the other hand, a diet that entirely relies on dietary fat is also not an option. Optimal consumption just so happens to be somewhere deep within that range. Much like carbs, fats are extremely easy to over ingest. Not only does fat content affect the flavor of food like meats, we often use oils to cook. Carbohydrates and protein contain four calories per gram. Fat contains nine calories per gram. The implication is again direct, not only are fats easy to over ingest, the ramifications of doing so result in double the caloric intake (comparatively), leading to faster weight gain. 

How Should You Eat?

Now that we have an understanding of caloric intake, how it’s measured, and how macronutrients react in our body, what does it all mean? It means you need to eat according to your goal. If your goal is centered around gaining weight and increasing muscle mass, eating in a caloric surplus and ingesting a high amount of protein is essential. Doing anything else would be counterproductive. If your goal is to reduce body fat, you must be in a caloric deficit. We learned that your body resorts to using stored fat as an energy source if you do this frequently enough, your body composition will change in your favor. We also learned that your body can, and will, use protein as a source of energy. This suggests that increasing protein intake while in a caloric deficit will help with the preservation of muscle mass. This is common practice for athletes looking to cut fat and maintain muscle. It is also possible to eat to maintain your current body composition. Eating at maintenance is done by eating the same number of calories you burn per day. If your total daily energy expenditure is 2,500kcal and you ingest 2,500kcal, the physical changes in your body should be minimal. Whether you’re eating to perform, gain, loss, maintain, or anything in between, adjusting your diet to coincide with your goals is essential to your progress.



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