How do calories factor into how much weight I lose?

Sharon Richter, RD
Nutrition & Dietetics
When it comes to weight loss, counting calories is not as important as eating nutrient-dense foods. Watch registered dietician Sharon Richter explain why eating protein, whole grains and fiber with each meal is a better strategy for weight loss.

You need to burn more calories than you consume to lose weight.  There are 3500 calories in one pound.  So if you reduced your calorie intake by 250 calories a day you would lose ½ pound every week.

A calorie is a measure of the energy value of food. According to experts, maintaining a healthy weight is often a calorie-balancing act -- making sure that the number of calories you eat balances with the energy you use in your daily activity.
  • If you eat more calories for a period of time, you'll gain weight -- unless you increase your activity level to offset the imbalance.
  • If you eat less or increase your activity, you can expect to lose weight. If you do both, you can expect to lose even more.
  • If you're using all the calories you're eating, you've achieved a balance that will allow you to keep weight off for the long term.
Whether weight is gained or lost is all based on the law of thermodynamics. This law dictates that in order to lose weight an individual must burn more calories than they are consuming. If there are more calories consumed than being burned through activity, then an individual will gain weight regardless of how much activity is taking place. To calculate the number of calories necessary for weight loss it is also necessary to know how many calories are being burned. The amount of calories burned varies with each individual and depends on body size, age, gender, and activity level. Using one of the many online calculators available is great for determining how many calories an individual is burning on a daily basis. There are also some electronic devices that a person can wear that will track more accurately track calorie burn. A quick internet search can provide more insight on these devices. A calorie is simply a measurement of energy, and 3,500 calories is equal to the energy potential in one pound of fat. With these facts, if an individual is burning 2,000 calories per day for a week, the total calorie burn is 14,000 calories. If the goal is to lose weight, this individual must consume fewer than 14,000 calories for that week. If only 10,500 calories are consumed, one pound will be lost.
Your body has energy needs. These needs take place every moment of every day. We measure these needs in energy units called calories. The secret to weight loss is first figuring out how many calories your body needs on a daily basis. There are a lot of ways to do this, some more accurate than others but I would recommend getting some help from a health and fitness professional. I would start by getting an accurate body fat percentage. From this and a few simple questions we can determine your caloric needs on a daily basis. This number will be what you need to keep your weight roughly the same. If you then take in less calories than this on a daily basis you will begin to lose weight (fat). If you take in more calories than this on a daily basis you will begin to gain weight (fat). It is pretty much that simple.
Dr. Mike Clark, DPT

Calories are everything when it comes to how much weight you lose. Losing weight is a simple math problem, and calories are the units we use to solve it.  Calories are a way for us to measure energy. With that said anything that we do – from the normal physiological processes that keep us alive, to physical activity – requires energy and thus, calories to do it. Foods also have a caloric value to them that’s based on the amount of energy-yielding nutrients (proteins, carbohydrates, fats, and fiber) that they contain.

To maintain your weight, the amount of calories you consume from food would have to equal the amount of calories your body burns on a daily basis – essentially canceling each other out. In order to lose weight you must consume less calories from food than the amount of calories you burn though activity and your body’s metabolism. When you create a deficit between how many calories you consume and how many calories you burn it requires your body to use stored fat for energy. We know that 1 pound of fat equals 3500 calories, so in order to reduce your weight by 1 pound a week, that would require you to create a deficit of 3500 calories (500 calorie daily deficit x 7 days); to lose more weight, simply create a bigger deficit. For example, reducing your food intake by 500 calories a day and increasing your physical activity to burn an extra 500 calories a day will create a 1000 calorie daily deficit, which will lead to 2 pounds of weight loss a week. 

Marisa Moore
Nutrition & Dietetics

The calorie equation is still considered the standard in weight management. The calorie equation states that calories in must equal calories out to maintain your weight. It holds that if you eat fewer calories than you burn (with daily activities, exercise, etc.) you will lose weight. Unfortunately the opposite is also true that if you eat more calories than you burn you will gain weight. 

To lose a pound a week, you must burn (or cut back on) about 3,500 calories over the course of the week. This equals about 500 calories a day. So that it's easier to manage, consider eating 250 calories fewer and burning an extra 250 calories per day in physical activity.
The only scientifically proven method for losing weight involves burning more calories than are taken in.

The number of calories a person needs each day depends on several factors -- body composition, height, weight, gender, age, and level of activity. Caloric needs vary a great deal among individuals. On average, the typical adult woman needs 1,500 to 2,000 calories each day to maintain her body weight and the typical man needs 2,000 to 3,000 calories. If more calories are consumed than the body needs, the excess is stored as body fat.

Body fat acts as an energy reserve; in other words, it’s stored and is converted into energy when the caloric intake is less than energy needs. Each pound of body fat has about 3,500 calories of energy.

The Weight Watchers program doesn't require you to count calories, but it teaches you to make healthy eating choices and to track your food choices and physical activity to help you lose weight.

Weight Watchers offers a comprehensive approach to weight loss that can help you reach your goals.
Enas Shakkour
Nutrition & Dietetics
Your body loses weight when you burn more calories than you consume. The amount of calories you burn depends on your age, sex, height, weight, and activity level. A registered dietician can give you an estimate of how many calories you burn. In order for you to lose weight, you must burn more calories than you consume. You can do that by reducing the amount of calories you take in and increasing your activity level. One pound of fat is 3,500 calories. If you burn an extra 3,500 calories, you will lose 1 pound of fat. You can lose 1 pound per week if you cut back on 500 calories every day.

It would only make sense to start this off with the one fact that is the basis for nearly all weight loss related information. All the tips, all the articles, all the methods, all revolve around making "one fact" take place. This is that fact:

Your body requires a certain number of calories per day in order to maintain your current weight. This is known as your calorie maintenance level. It's the number of calories required by your body to do everything it needs to do (intense exercise, brushing your teeth, pumping blood, keeping organs functioning properly, etc.). Calories are what our bodies use for energy, so in order to do what needs to be done, a certain number of calories are needed.

As you know, we supply our bodies with these calories through eating and drinking. If we end up consuming exactly the same number of calories that our bodies need each day, our weight would remain exactly the same. For example, if your calorie maintenance level was 2500 calories, and you consumed 2500 calories per day, your weight would not change. All of the calories you take in would end up being burned. This is how you maintain your weight, by giving your body only the calories that it needs. No more, no less.

However, if you do consume more calories than this maintenance level, your body will store the excess calories as fat. So, for example, if your maintenance level was 2500 calories, and you consumed 3000 calories per day, you would gain weight. You are giving your body more calories than it would end up burning. This is what causes weight gain.

On the other hand, if you do the opposite and give your body less calories than it needs, your body will convert your stored body fat into energy and use that instead. This is what causes weight loss. Sticking with the same example as before, if your daily maintenance level is 2500 calories, and you consume 2000 calories per day, you will lose weight.

Basically, consume the same number of calories that your body needs and burns each day and you maintain your weight. Consume more calories than your body needs and burns and you gain weight. Consume fewer calories than your body needs and burns and you lose weight.

Wendy Batts

There is a direct relationship between the weight we lose and calories. The calorie is the unit we use to measure how much energy is in food (in the form of carb, protein, fat, alcohol) and how much energy we store or use (body fat and body sugar stores).

So the direct relationship looks like this: one pound of fat on our bodies is equal to 3500 calories. We need to burn more calories than we eat to give our bodies a reason to use stored energy, which is exactly what body fat is: stored energy. So for every 3500 calories we burn above what we eat, we use 3500 stored calories. Keep in mind this doesn’t’ mean that we can try to create this gap within a single day. This would be unhealthy and have other negative effects on our health and energy levels.

For example to lose one pound per week, we would need to burn 3500 calories more than we ate over the course of that week. Another way to think of that is we would need to burn 500 more calories per day than we consume. We can accomplish this by incorporating a sensible reduced calorie diet and increased physical activity.

Dee Sandquist
Nutrition & Dietetics

Calories do count; however, you need to count every single one. It's a balance over time of calories eaten vs. energy used. Want to simplify without the calculator? If you eat more one day, eat less the next. Yes, that's easier said than done, I do know. In addition to reducing calories (100 per day is all you need to do) increase your physical activity. Park at the back of the grocery store lot instead of circling until you get a prime parking spot. Take a 10 minute walk twice a day to start. In no time, you'll feel better and will want to increase to 20 minutes per day. Another strategy for balancing calories is to eat 2/3 of what you currently eat. Just put the fork down. Don't deprive yourself if you crave a sweet treat. Eat two bites slowly and chew thoroughly. You may find that's enough to satisfy the craving instead of wolfing down the whole sweet treat. The bonus is that you'll feel better and have more energy.

Marjorie Nolan Cohn
Nutrition & Dietetics

Simply stated, if you take in more calories than you need on a daily basis, the excess calories turn into extra weight. Think of food as fuel and your body as a car. Food is the energy your body "runs" on. Overeating is like over-fueling; any excess fuel you don't "run on" turns into fat. This is how weight gain occurs. Because of this basic principle (calories consumed versus calories spent), the cause of weight loss is just as straightforward as the explanation of weight gain. If you consume fewer calories than you burn, you will lose weight. The basis of every weight loss diet is based on this. Whether you follow a low-fat or low-carbohydrate/high protein diet or you reduce portion sizes, all varied means to the same end: fewer calories consumed.

Controlling your weight isn't a magic trick, rather it's simple math. Maintaining your weight in a healthy range requires a balance between the calories you take in through food and drink and the calories you burn through physical activity.

A good mind-set for approaching calorie control is to think of the calories you consume and the calories you burn as your calorie budget. How do you want to "spend" those calories?
  • To lose weight: Consume fewer calories than you burn each day. Either cut back on the calories you consume, exercise more or do both.
  • To gain weight: Tip the balance the other way. Take in more calories than your body uses. However, your body still needs physical activity to remain healthy, so keep moving.
Why focus on calorie balance? Your body stores most of the excess calories you consume as fat. Just 100 extra calories a day adds up to 10 pounds in a year.
James O. Hill
Nutrition & Dietetics
One of the secrets of effective weight loss is paying attention -- and keeping close track of your calories is one way to make sure you're paying attention. When people report their food intake, they're nearly always eating more than they think they are.
Joel H. Fuhrman, MD
Family Medicine
Calorie-counting is a popular dieting method. In this video, nutritional researcher and author Joel Fuhrman, MD, explains why the practice can backfire.
Calories can affect your weight by increasing it or decreasing it. All considerations aside it can even keep it the same weight. One pound is equal to 3500 calories. So when we are looking at losing weight we must be sure to burn more calories than we eat. When we are looking to add weight, we must eat more than we burn (it is recommended that they are healthy calories). Do not just eat whatever and say you are eating more than you burn. And if you have reached your goal weight and want to maintain that be sure to eat as many calories as you burn. One-way to help determine how many you burn daily is an Exerspy ... great calorie management program. One thing you need to realize when it comes to calories and weight is that the process does not happen overnight. It takes determination and belief in you. It takes time and commitment, but with the right goals and motivation anything is possible.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.