You’ve probably heard the word calories before and know that it has something to do with food. Many people try to restrict the number they take in when trying to lose weight. This can be effective, but is that all you need to know? Are all calories the same? How do you figure out how many calories you should eat?

Most people probably think of calories in one of two ways: either in terms of the food they consume or in relation to what they burn through exercise. While both of these are true, calories are just a measure of energy.

There are two types of calories. A small calorie (cal) is the amount of energy required to raise the temperature of 1 gram (g) of water by 1º Celsius (º C). A large calorie (kilocalorie or kcal) is the amount of energy required to raise 1 kilogram (kg) of water by 1º C. The conversion is 1 kcal is equal to 1,000 cal.

To determine how much energy a particular food contains, researchers burn it in a device known as a bomb calorimeter. The heat from the reaction will raise the temperature of the water in the device. The temperature change indicates the amount of energy in the food itself. While the terms “large calorie” and “small calorie” are often used interchangeably, this is misleading. When looking at food labels, the calorie content described refers to kilocalories. So, a 250-calorie food product really contains 250,000 calories.

When it comes to the calorific values of food, there are three main components, or macronutrients—carbohydrates, protein, and fat. Each one provides a different energy level, with 1 g of either carbohydrates or protein equaling 4 kcal, and 1 g of fat containing 9 kcal. To create energy, our bodies convert these nutrients into glucose (the simplest sugar). It fuels all the processes within the body. Without it, we wouldn’t survive.

Our bodies are designed to use carbohydrates for energy because they consist of hundreds of glucose molecules linked together, easily broken down. Proteins and fats have to be converted into glucose. While this makes them less efficient for the body, it doesn’t mean they aren’t necessary. Proteins are essential for building muscle or antibodies to prevent sickness. Healthy fats, like omega-3 fatty acids and monounsaturated fatty acids, help your body absorb vitamins and reduce the risk of heart disease and type 2 diabetes.

All the calories you eat are either converted to physical energy or stored within your body as fat. When you eat more calories than you need, your body converts them into muscle (short-term storage) or fat tissues (long-term storage). These stored calories will remain in your body until you use them up, either by reducing calorie intake so that your body must draw on reserves for energy or increasing physical activity so that you burn more calories. This is your body’s natural survival mechanism because if you aren’t able to eat enough, it’ll tap into these stores for fuel.

The Centers for Disease Control and Prevention (CDC) refers to the balance of calories burned and calories consumed as caloric balance. Your body will maintain its weight when the calories consumed are the same as the calories burned. If you take in more calories than you burn, you’ll gain weight. If you’re burning more calories than you are eating, you’ll lose weight.

This is why consuming the correct number of calories is vital.

The National Academies of Sciences, Engineering, and Medicine recommends that Dietary Reference Intakes (DRI) for an adult are 45 – 65% of calories from carbohydrates, 20 – 25% fat, and 10 – 35% protein. The reason for the variability is that everyone requires different amounts of energy each day. Numerous factors, such as age, gender, weight, height, overall general health, and activity level, impact the specific amount each person should consume. Taking in the correct number of calories every day can lead to a healthy life, whereas consuming too little or too many will eventually lead to health problems.

When trying to lose weight, a good practice is to reduce your calorie intake to 500 fewer calories than your body needs to maintain your current weight. This will help you lose about 1 pound of body weight per week. A 1–2 pound decrease in weight per week is considered a healthy and sustainable rate.

Since women are typically smaller in size than men, their caloric needs are usually less. The recommendation for the average, moderately active woman between the ages of 26–50 should eat about 2,000 calories per day to maintain her weight. Active women should take in 2,200 calories or more daily to maintain their weight. Women in their early 20s have higher calorie needs, and those over 50 generally require fewer calories. None of these estimates apply to women who are pregnant or breastfeeding because their caloric needs are significantly higher.

The recommendation for the average, moderately active man between the ages of 26–45 is 2,600 calories per day to maintain his weight. Active men may need 2,800–3,000 calories per day to maintain their weight. Similar to women, younger men need more calories, and older men need fewer. Some experts estimate that if you consume approximately 3,500 excess calories, you’ll gain one pound.

There’s often a great deal of confusion when it comes to calories in food. Part of this is because calorie count alone does not whether a food is nutritious. It’s more about the type of calorie, such as does it supply vitamins, minerals, and fiber. If it doesn’t, it’s usually referred to as an “empty calorie.” These calories are those that provide energy but very little nutritional value.

According to (the US Department of Agriculture’s diet management tool), empty calories come mainly from solid fats and added sugars. While solid fats exist naturally in many foods, they’re regularly added during industrial food processing and food preparation. Solid fats are fats that solidify at room temperature. Think butter. Other examples of solid fats are ribs, bacon, hot dogs, sausages, cheese, and pizza.

Added sugars are put in foods and beverages during industrial processing. The most common types are sucrose and high-fructose corn syrup, which are supposed to make foods and drinks more enjoyable. They’re found in fruit drinks, sports drinks, energy drinks, and soda. Studies show that sugary drinks are the leading source of empty calories for people in the US, with over half of all people having at least one each day. A recent study shows that drinking more than one sugar-sweetened beverage a day increases your risk of high blood pressure.

Some foods contain solid fats and added sugars, like ice cream, donuts, pastries, cookies, and cakes. Alcohol can also contribute empty calories to the diet.

These types of foods are also considered high-calorie or calorically dense, which means they have a high amount of calories relative to their serving size. Most often, high-calorie foods are associated with junk food, but some are high in nutrients. Healthy foods that are high in calories include avocados, quinoa, nuts, olive oil, whole grains, and dark chocolate (in moderation).

Foods that are considered low-calorie have a low amount of calories relative to their serving size. Fruits and especially vegetables fall into this category. According to the USDA Nutrition Database, two cups of shredded romaine lettuce or spinach have 16 calories, a large stalk of celery has ten calories, one large ear of corn has 123 calories, one cup of broccoli has 15 calories, and an orange has 70 calories.

When trying to lose weight, people often restrict calories. This can help, but not if you limit them too much. According to the National Institutes of Health (NIH), low-calorie diets provide 1,000 to 1,200 calories per day for women and 1,200 to 1,600 calories per day for men. Very low-calorie diets only provide up to 800 calories a day. The problem is eating 800 or 1,000 calories a day lowers your resting metabolic rate over time.

Lower-calorie diets also put you at risk of losing lean muscle mass. Both ultimately impact how many calories you burn. When you have more muscle, you are better able to stay active during the day and burn more calories. Low-calorie diet plans consist of regular food but sometimes contain meal replacements. As a result, they’re not something that works long-term. When people return to their regular caloric intake, they regain the weight that they lost. Unfortunately, the loss of muscle mass that happens during a low-calorie diet means that regained weight is usually fat.

According to the NIH, very low-calorie diets are special diets that must be done under the guidance of a healthcare provider. All meals are replaced with prepared formulas, often liquid shakes, which aren’t the same as shakes and other meal replacements found commercially. People prescribed these diets are usually obese and face serious health problems like diabetes, high blood pressure, and high cholesterol.

A different approach, that’s effective, is to restrict not only how much but how often you eat. This is referred to as intermittent fasting. There are various types, but it typically includes fasting for a period of time each day or having a low-calorie intake day once a week. The concept of intermittent fasting is gaining some popularity, especially after a series of animal studies showed that it increased longevity. A 2014 review in the journal Cell Metabolism discovered that in humans, intermittent fasting might help “reduce obesity, hypertension, asthma, and rheumatoid arthritis.”

It can seem overwhelming if you’re trying to decide to eat healthier and lose weight. However, there are some strategies you can follow. The first, and most important, is keeping track of your calorie intake because this will help you better understand the number of calories your body needs to lose, gain, or sustain a certain weight.

To determine how many calories your body needs to maintain its current weight (if you’re moderately active), multiply it by 15. The next step is calculating the number of calories you need to consume to lose weight. Then, keep track of how many calories you’re ingesting by using this calorie counting method. Try it for at least a few days to see how many calories, carbs, protein, fat, fiber, vitamins, and minerals you’re eating. There are many websites and apps available.

The next tip is to eat more protein. Several studies demonstrate that protein not only helps curb your appetite, but it increases your metabolic rate. This is because protein requires energy to metabolize. Select lean types of meat over fatty ones.

Besides increasing protein intake, you should reduce your consumption of refined carbs. Multiple studies have proven that eating a low-carb diet can make you lose about two to three times more weight than a calorie-restricted, low-fat diet. The key is to ensure that you’re eating quality, fiber-rich carbs. Try choosing low-fat options and skipping high-calorie, low-nutrition items. Think about what you eat and drink each day. Identify items you could cut out. If you think that skipping something will leave you with a craving, try a low-calorie substitution.

A critical step is to have a regular eating schedule. Research shows that having meals and snacks planned for specific times each day is the most successful way to lose weight and keep it off. Also, don’t skip breakfast. In fact, have a hearty one because it can help the body to use calories more effectively. The journal Obesity featured work from researchers at Tel Aviv University, who wrote that a large breakfast containing approximately 700 kcal is ideal for losing weight and lowering the risk of diabetes, heart disease, and high cholesterol.

It’s vital to reduce portion sizes because this can significantly affect how many calories you’re getting. Most of us aren’t good at estimating how much food is too much. It’s easy to underestimate how much you’re eating, especially if you’re dining out. Part of this is not confusing a serving with a portion.

  • A portion is the amount of food you put on your plate.
  • A serving is the amount you’re supposed to eat to receive a certain number of calories and nutrients.

A way to make sure you don’t overeat is to take slightly less than what you think you’ll eat at the beginning of the meal. If you’re still hungry, eat more vegetables or fruit.

Before eating, always check food labels for the serving size and number of calories per serving. Often, packages that we think have only one serving contain two or more. Another common finding is that some fat-free foods contain more calories than the regular versions because manufacturers use extra sugar to make up for the flavor lost in removing the fat. Don’t eat from packages because you don’t have a sense of how much you’re eating. When you put food on a plate or in a bowl, you’re more aware of how much you’re eating. A pro tip is to use a smaller plate or bowl because it looks like you’re eating the same amount.

An obvious choice is to avoid sugary soft drinks and fruit juices. Part of the issue with these is that your brain doesn’t register liquid calories the same way it records solid calories. It doesn’t automatically compensate by having you eat smaller amounts of other things instead. If you want something sweet, try eating fruit because it also contains fiber and other essential nutrients.

It’s vital to drink more water. Some studies have indicated drinking water can increase the number of calories you burn for up to 90 minutes. It’s also helpful to drink water immediately before meals since this can reduce hunger and make you eat fewer calories.

Exercising and lifting weights are essential because muscle is metabolically active. So, the only proven strategy to prevent your body from losing it, especially if you’re reducing calories, is to exert them. If you can’t get to a gym, try bodyweight exercises, such as pushups, squats, and sit-ups, at home. Be sure to do some cardio, like walking, swimming, or jogging, too. Moderately active is getting at least 30 minutes of physical activity a day, such as walking at a brisk pace, climbing stairs, or active gardening. To aid in losing at least a pound a week, try to do at least 30 minutes of physical activity on most days.

When it comes to calories, it’s important to select ones that are nutritious and not empty. Unfortunately, this takes a conscious effort because many typical American foods have a lot of these calories. By being more aware of the type of calories you consume, you’ll be on your way to having a healthy life at the weight you desire.