Knowing how many calories you need to consume each day is essential for losing, gaining, or maintaining weight. One way to determine this with a technique called the Harris-Benedict formula, which is one method used to estimate your basal metabolic rate (BMR). Show By definition, BMR is your rate of metabolism (the conversion of calories and oxygen to energy) at rest. It is the minimum level of energy required to sustain vital functions such as breathing, digestion, and circulation. The Harris-Benedict formula is often used to assist weight loss by ensuring that you reduce the intake of calories below what you need to maintain weight. The Harris-Benedict formula is used to describe your basal metabolic rate (BMR) as a numeric value. Your BMR is determined by your sex, age, and body size, and calculating this number tells you how about how many calories you burn just being alive and awake. The formula for the BMR is quite complex.
Once you get out of bed and begin to move around, you will need to adjust this figure as you expend more energy. This value, called active metabolic rate (AMR), is calculated by multiplying your BMR by an assigned number representing the various activity levels. This number ranges from 1.2 for being sedentary up to 1.9 for being very active. Calculate your AMR by multiplying your BMR and by your current level of activity.
Your AMR represents the number of calories you need to consume each day to stay at your current weight. If you want to lose weight, you need to increase your level of physical activity or decrease your caloric intake by eating less. For the purpose of weight loss, the AMR provides you the means to figure out how many calories you either need to exclude and/or how many calories you need to burn through added exercise, to lose a specific amount of weight. For example, if your BMR is 1,400 (the average for American women) and you are moderately active, your AMR would be 2,170 (1,400 x 1.55). Since a pound of fat is equal to 3,500 calories, you would need to cut 500 calories per day to lose a pound per week. This is called your calorie deficit. If you plan to lose weight simply by diet, your daily calorie intake would be 1,670 (2,170 - 500 = 1,670). If you plan to do it by exercise alone, you would need to burn 500 calories each day above and beyond what you already do. For this reason, a combination of diet and exercise almost always achieves the best result. Unfortunately, the Harris-Benedict formula isn't exactly perfect. According to the Academy of Nutrition and Dietetics, research studies have indicated the formula is about 90% accurate around 60% of the time. That means it could be way off about 40% of the time, which is rather disheartening. Even worse, when the formula was wrong, it overestimated the calorie needs of the research subjects, meaning that they were burning fewer calories than they thought. The problems may be due to physical or genetic factors that impede or enhance metabolism in some people. Moreover, there's a good chance that many people overestimate how physically active they are. Despite these shortcomings, the Harris-Benedict formula provides you with a relatively good picture of your general caloric needs. If you don't achieve weight loss based on the calculations, simply adjust your daily calorie count up or down or recalculate your AMR based on a lower activity level.
Never consume less than 1,200 calories per day without medical supervision. Doing so can send your body into starvation, slowing metabolism and increasing the risk of gallstones, gout, fatigue, irregular periods, and malnutrition. Though it really isn't difficult to grab a calculator and figure this all out by hand, there are plenty of online calculators that shortcut the process. Online calorie calculators make the perfect starting place for anyone who wants to get their calorie counts under control. You can also find nutritional calculators and exercise calculators that keep track of the calories you burn each day.
An ideal daily intake of calories varies depending on age, metabolism and levels of physical activity, among other things. Generally, the recommended daily calorie intake is 2,000 calories a day for women and 2,500 for men. Calories are a measure of how much energy food or drink contains. The amount of energy you need will depend on: Other factors can also affect how much energy you burn. For example: The term calorie is commonly used as shorthand for kilocalorie. You will find this written as kcal on food packets. Kilojoules (kJ) are the equivalent of kilocalories within the International System of Units, and you'll see both kJ and kcal on nutrition labels. 4.2kJ is equivalent to approximately 1kcal. To find out if you are a healthy weight, use the BMI calculator. To maintain a healthy weight, you need to balance the amount of calories you consume through food and drink with the amount of calories you burn through physical activity. To lose weight in a healthy way, you need to use more energy than you consume by eating a healthy, balanced diet with fewer calories while increasing your physical activity. For more information on weight loss, download the NHS weight loss plan, our free 12 week diet and exercise plan. A GP can also give you advice about losing weight. You should get advice from the GP if you're underweight (your body mass index is less than 18.5). To gain weight, you need to eat more calories than your body uses each day. For more information, see How can I gain weight safely?. Further information
Page last reviewed: 24 October 2019  We include products we think are useful for our readers. If you buy through links on this page, we may earn a small commission. Here’s our process. Every day, you burn calories when you move around, exercise, and go about your daily tasks. Most female adults need 1,600–2,200 calories per day, while adult males need 2,200–3,000 calories per day. However, the amount of calories you need each day is unique to your body and activity levels (1). Calories are important for basic bodily functions, such as:
You also burn additional calories from everyday movements, as well as exercise, which can vary considerably from person to person. If you’ve ever wondered how many calories you burn each day, the Mifflin-St Jeor formula can help you figure this out. This formula calculates your resting metabolic rate (RMR), also known as your resting energy expenditure, which is the number of calories your body needs to function at rest. With one more calculation, which considers your activity levels, you can work out how many calories you need each day to maintain your current weight. Eating fewer calories than this will likely result in weight loss, while eating more calories than this will likely lead to weight gain. This article teaches you how to calculate your calorie needs based on your health goals.
The number of calories you should burn in a day largely depends on your personal health and fitness goals, as well as other factors like your age, sex, height, weight, and activity levels. To lose weightTo lose weight, you must be in a calorie deficit. This means you’re either eating fewer calories than your body needs, burning additional calories, or a combination of both. For sustainable weight loss, an ideal calorie deficit will be around 10–20% fewer calories than your total daily energy expenditure (TDEE). Let’s say that your body needs 2,200 calories per day. A calorie deficit of 10–20% would be 1,760–1,980 calories per day (Equation: 2,200 – (2,200 × 0.1) = 1,980 or 2,200 – (2,200 × 0.2) = 1,760). While you can achieve weight loss quicker with a larger calorie deficit, it may be difficult to sustain long term since it will likely lead to significant hunger. Your body may employ mechanisms to prevent further weight loss, such as sluggishness or a reduced metabolic rate (2, 3). Furthermore, too large of a deficit can lead to loss of lean muscle. A mild calorie deficit paired with resistance training can help preserve lean muscle mass while also promoting fat loss (4, 5, 6). That said, weight loss can be influenced by a variety of factors, such as age, genetics, hormones, medical conditions, and medications. Therefore, you may need to work with a healthcare professional who can develop personalized recommendations for you (7). To maintain weightIf you’re looking to maintain your weight, you’ll want to ensure your calorie intake matches your calorie expenditure. To figure this out, you’ll need to calculate your TDEE, which is the number of calories your body needs to sustain the weight you’re currently at. If you notice that you’re gaining weight, this is likely a sign that you’re either consuming more calories or expending fewer calories than you intend to. If you’re losing weight, you’re liking not eating enough calories or expending too many calories. To gain weightIf you want to gain weight, you need to be in a calorie surplus. This means that you’re either eating more calories than your body needs, expending fewer calories, or a combination of both. As in the case of a calorie deficit, you’ll want to do this slowly to ensure it’s healthy and sustainable. A mild calorie surplus of around 10–20% will allow for slow, gradual weight gain. If your calorie needs are 2,200 calories per day, a calorie surplus of 10–20% would be 2,420–2,640 calories per day. While it may seem obvious to eat a very large amount of calories and limit your physical activity, this strategy isn’t ideal, as it will likely lead to excessive fat accumulation and removes the important health benefits of exercise (8). Ideally, choose nutrient-dense foods that are higher in calories to support gradual weight gain. Examples include:
If you struggle to eat large meals, you may want to eat smaller meals more frequently. You may also want to cut back on your physical activity if you’re extremely active. For example, you may wish to reduce the time, frequency, or intensity of your exercise. In some cases, your healthcare professional may want you to gain weight quicker, so be sure to listen to their advice. The Mifflin-St Jeor equation is an easy way to calculate how many calories you need to eat per day, and it’s considered one of the most accurate formulas. It’s adjusted based on your sex, age, height, and weight to give a personalized estimation (9). This equation was first published in 1990 as an updated formula that better predicts a person’s energy expenditure than the previously used Harris-Benedict equation (10). Once you calculate your resting metabolic rate (RMR), you can multiply this figure by an activity factor based on your daily activity level — ranging from sedentary to very active — to find out the number of calories you need to consume each day to maintain your weight. The next sections will tell you how to do these calculations. If you’re looking for a quick answer, you can use our handy online calculator to do the legwork for you. Your RMR is the number of calories your body needs to function, and it does not include your daily physical activity and other movements. To calculate your RMR, use your sex, age, height, and weight to adjust the formula. The formulas for calculating this number are as follows, using kilograms for weight, centimeters for height, and years for age (9). For males, use the following equation:
For example, a 40-year-old, 180-pound (81.6-kg), 6-foot (183-cm) tall man has a BMR of 1,767. This means that, at rest, he’ll burn approximately 1,769 calories in a day (Equation: (9.99 × 81.6 kg) + (6.25 × 183) – (4.92 × 40) + 5 = 1,767). For females, use the following equation:
For example, a 40-year-old, 150-pound (68-kg), 5’6” (168-cm) woman has a RMR of 1,372 (Equation: (9.99 × 68 kg) + (6.25 × 168) – (4.92 × 40) – 161 = 1,372). Keep in mind that this number calculates your RMR, or resting energy expenditure, which does not account for any movement throughout the day. You would not use this as the final number for your calorie needs. Step 2. Work out your activity levelFrom there, you must figure out your activity level. The activity levels the equation uses are as follows (11):
For example, a postal worker who walks all day for their job would have an activity level of 1.725depending on the length and difficulty of their route. A desk worker who walks several times a week for exercise would have an activity level of 1.55. Step 3. Use the full equationPutting everything together, the Mifflin-St Jeor equation is as follows:
A 150-pound (68-kg) female who’s extra active will need 2,611 calories to maintain their weight (Equation: 1,372 (RMR) × 1.9 (activity level) = 2,607 calories). A 180-pound (81.6-kg) male who’s moderately active will need 2,742 calories to maintain their weight (Equation: 1,767 (RMR) × 1.55 (activity level) = 2,739 calories). As you can see in the above examples, a person’s activity level has a lot to do with how many calories they need each day. Many people think they need to exercise hard to burn calories throughout the day. While exercise does burn a lot of calories, your body also burns calories while you’re doing normal daily tasks. How much you burn has to do with how much you weigh. For example, people will burn the following number of calories in 30 minutes of doing these tasks based on their weight (12): Note that your exercise habits affect how many calories you burn at rest. While aerobic activity may burn more calories during the training session, researchers have found that resistance exercise increases resting metabolic rate for up to 14 hours after exercising (13, 14). You can use an interactive online calculator to find out how many calories you’ll burn while doing different activities. To use it, simply input your activity, the time spent doing it, and your weight. Yes, males and females burn calories at different rates. This is why sex is included as a variable in the equation, along with age and weight, which also affect the number of calories a person burns. People assigned male at birth generally have less body fat than people assigned female at birth. They also tend to have more muscle mass. More muscle means the body burns a higher number of calories while at rest. So, generally, males usually burn more calories than females overall. That said, a person’s body composition plays an important role, as do hormone levels. Losing weight isn’t always as simple as plugging numbers into a calculator. The most effective way to lose weight and keep it off in the long term is to follow a balanced lifestyle that includes:
Some people also find these tips can help when they’re trying to lose weight:
Shop for food diaries to help get you started. And check out the best calorie counter websites and apps here. If you’re struggling to gain or lose weight, you may want to see a healthcare professional who can provide personal recommendations. Lose weightIf you aren’t losing weight despite increasing your physical activity and decreasing your food intake, you may want to visit your primary care professional. They can assess your current lifestyle habits, medications you’re taking, any medical conditions, family history, and other factors that may be preventing you from losing weight. You may also be referred to other specialists, such as a registered dietitian, who can provide a detailed assessment of your diet and give personalized suggestions to help you achieve weight loss based on your unique situation. If an underlying hormonal condition is suspected, such as hypothyroidism, they may refer you to an endocrinologist. Gain weightIf you can’t put on weight or are losing weight unintentionally, it’s important that you speak with your primary care professional as soon as possible. In some cases, this could be a sign of an underlying condition like hyperthyroidism or cancer. They may also refer you to a registered dietitian who can assess your diet and provide suggestions to increase your calorie intake in a healthy way, or a physical therapist who can help you build muscle. The amount of calories you need each day is unique to your body, lifestyle habits, and health goals. While the average male and female need roughly 2,200–3,000 and 1,600–2,200 calories per day, respectively, your needs may differ depending on your height, weight, and activity level. Learning how to calculate your individual calorie needs is a good way to know whether you’re on track with your health and fitness goals, such as losing, maintaining, or gaining weight. That said, if you’re looking for personalized recommendations or struggling to achieve specific health goals, talk with a healthcare professional who can give a more thorough assessment. Last medically reviewed on November 30, 2021 Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available. Nov 30, 2021 By Katey Davidson, MScFN, RD, CPT Medically Reviewed By Micky Lal, MA, CSCS,RYT Copy Edited By Christina Guzik, BA, MBA Jul 1, 2020 Medically Reviewed By Kathy Warwick, RD, LD Copy Edited By Delores Smith-Johnson |
How many calories does the body need to function
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