What are calories?
The term “calories” means units of energy and has different meanings depending on who uses it – for instance:
- In science, a calorie is the amount of heat energy required to increase the temperature of 1 gr of water by 1 degree Celsius.
- In food labels, a calorie is the amount of energy in food, whereas 1 food calorie is actually a “kilocalorie” (kcal) and equals 1000 calories used in scientific measurements.
Calories have no smell, taste or appearance. You can only measure them using special equipment or tests or deduce them from what they do to your body weight. Calories measure the energy you take through food, and they aren’t a measure of your weight. Your body uses the energy as fuel for various activities such as breathing, reading, working out, moving heavy boxes, cooking, etc. Even sleeping requires a small amount of energy. Each activity burns a specific number of calories.
The more active you’re during the day, the more calories you burn. Also, if you burn more calories than you consume through food each day, you’ll lose weight. However, if you burn fewer calories than you consume, your body will convert the unused calories to body fats and store them. That stored fat will increase your weight.
How are calories in food calculated?
The Atwater system calculates the number of calories in each nutrient. Food manufacturers use this method to measure and add up the calories provided by each macronutrient (proteins, carbohydrates and fats) contained in a product. The total number of calories is then printed on the package label of the same product.
What are empty calories?
Empty calories are a type of calories that are particularly unhealthy. They’re present in foods that are high in calories but low in nutrients – for example, soft drinks, salty snacks and sweets. Fast foods and packaged meals also contain large amounts of empty calories.
For example, a complete fast-food meal may contain as many calories as you need in a whole day. Such a meal will fill you up and supply your body with energy. However, it will also be full of salt, unhealthy fats and sugar. The amount of beneficial nutrients in the meal will also be very low.
Calories in macronutrients
Macronutrients provide most of the energy your body needs. There are three types of macronutrients: carbs, proteins and fats.
Proteins
Proteins are essential for your growth, muscle strength and bone sturdiness and for repairing injuries. They’re made of chains of molecules called amino acids. Every gram of protein contains 4 kcal, about half the kilocalories in a gram of fat. This macronutrient is present in red meat, fish, nuts, dairy products, legumes and poultry.
Carbohydrates
Carbohydrates are a type of macronutrient that you need in large amounts, and they’re made of sugar molecules. Depending on the number of molecules each carbohydrate is made of, there are two types of carbs: simple and complex. Simple carbs contain one or two small sugar molecules, while complex carbs have many large sugar molecules.
Every gram of carbs (complex or simple) you consume equals 4 kcal. However, according to dietitians, the calories from complex carbs are better for your health than those from simple carbs. That’s because the sugar from complex carbs stays longer in your bloodstream and raises your glucose levels slower than the sugar from simple carbs.
Fats
Another type of macronutrients is fat. All types of fats (saturated, unsaturated and trans) are high in calories in comparison to the other macronutrients (proteins and carbs). One gram of fat contains 9 kcal. You should consume mainly unsaturated fats and avoid trans fats completely. The consumption of saturated fats (e.g. red meats and dairy) should be minimal. Unsaturated fats are present in fish, nuts and avocado. Cookies, chips, candy bars and other processed foods have trans fats.
Calories in alcohol
Alcohol typically contains no nutrients or so few (mainly sugars) that they’re hardly worth mentioning. However, alcoholic beverages most certainly contain calories. Usually, 1 gram of alcohol has about 7 kcal, and a standard serving of 15 grams of pure alcohol has 105 kcal.
Interestingly, alcohol doesn’t change during digestion. It’s absorbed by the body intact and sent straight to the liver. The enzymes then convert it to acetaldehyde, a potentially toxic substance that can damage the liver, heart and other organs. People who drink small amounts of alcohol will readily metabolise acetaldehyde to acetate. Acetate is excreted as carbon dioxide and water or stored as body fat if calories are in excess. But, if large amounts of alcohol are consumed, the fat deposition in the liver is increased, and the body cannot metabolise acetaldehyde. When this substance accumulates, it causes damage to the liver and the heart.
How many calories do you need?
The number of calories you need a day depends on many factors, including gender, age, weight and height. But most importantly, it depends on your level of daily physical activity and exercise. For instance, a person who has a sedentary lifestyle and spends most of their day in front of a laptop burns less energy than a construction worker who carries tools, loads and unloads materials, assembles temporary structures and breaks down barricades.
According to the estimated energy requirements (EER) table of the US National Library of Medicine, a woman in her 30s who weighs about 55 kilograms may burn as many as 3000 kilocalories on a day when doing vigorous activities. But, if she spends most of the day reading and sleeping, her body will burn about half of that calorie count. Likewise, a man who weighs 70 kilograms may burn as many as 4000 kilocalories and as little as 1700 kilocalories, depending on his level of physical activity.
Health issues caused by too many calories
One of the main issues with taking in too many calories is that the unused ones become fats stored in your body. And while a certain amount of stored fat is healthy, excess fat can create serious health issues. For instance: diseases of the heart and circulatory system, liver issues, diabetes, arthritis and even some forms of cancer.
How to balance calories intake and daily activities
Dietitians and other health professionals recommend that everyone adopt a smart lifestyle, which includes the following:
- Routine movements that burn energy
- Daily exercise, such as playing volleyball for an hour every day, having long walks in the park, cardio workouts, etc.
- Nutritional meals that include lots of veggies, fish and starches.
- Snacking with healthy foods – for instance, a cup of fruit, a couple of spoons of peanut butter, etc.
Understanding food labels
Nowadays, all packaged foods must be labelled with nutrition facts. This type of label provides consumers with information about a food’s nutritional values and calorie count. Usually, the calorie count is the first thing consumers look for. The nutritional table on the label contains information about the type and quantity of macronutrients and micronutrients contained in the product. For instance, how many grams of protein a packaged product has. A product’s food label also states the size and number of servings per package. The estimated serving size is determined by the producer and is not an exact measurement. However, it indicates the portion an average person will eat.