Most people are familiar with the golden rule of weight loss; eat less and move more. It is commonly said that you have to create a 500 kcal per day deficit through some combination of diet and exercise in order to lose one pound of body weight each week.
If this advice is accurate, dieters should be able to follow this formula and consistently lose weight until they reach their weight loss goal.
In the real world, people often are able to lose weight in the short term but have a hard time keeping it off. In fact, most people who lose weight eventually gain it all back. Some even gain back more weight than they had lost in the first place (1).
Unfortunately, the 500 calorie rule relies on a flawed assumption about the human body and the number of calories contained in one pound of body fat.
This article will explain the truth about body weight. It will discuss how many calories are really found in a pound of fat and show what you need to do next time to achieve lasting and sustainable weight loss once and for all.
What Is a Calorie?
A calorie is a unit of energy. Calories are used to measure the amount of potential energy stored in food. Our bodies use energy from calories to fuel our metabolism and all of our daily activities.
All food contains calories, but some foods are much more calorie-dense than others.
For example, foods such as soda, donuts, and ice cream have a high-calorie density because they are loaded with fat and sugar. Other foods like broccoli and lettuce provide very few calories per serving.
These differences are driven by the different macronutrient composition of foods.
The macronutrient building blocks of food are carbohydrates, proteins, and fat. When broken down through the process of digestion, each of these nutrients provides a certain amount of energy for our body.
Every gram of carbohydrate and protein in food provides about four kcals of energy. Fat provides more than twice that amount; each gram of fat provides around nine kcals.
Since fat provides more than twice as many calories as protein or carbs per gram, it is more efficient for our body to store excess calories in the form of fat.
What Is Body Fat?
Body fat can be thought of as savings account for extra calories and energy. Because calories are so valuable our body needs an efficient way of storing them.
Our liver can store a small amount of extra energy in the form of glycogen, the storage form of blood sugar. However, the vast majority of the excess calories in our body are stored as fat.
People often confuse body fat with the dietary fat found in food. Fat in food is also stored energy, however that fat does not get stored directly in body fat.
After eating a meal containing dietary fat, our body breaks it down so it can be absorbed. It then circulates in our blood where it is used for different metabolic purposes.
Any excess fat that our body does not immediately need is taken up and stored as fat in the body. But it is not just extra fat that is stored away, extra protein and carbohydrates can be converted to fat and stored in fat cells as well.
This process happens with every meal. The difficulty is for many people is that they eat additional calories beyond what is needed to keep their body in energy balance for a long period of time.
Extra energy continues to be stored away and stays in the body long term. Eventually, this leads to the development of obesity, now recognized as a chronic disease.
There are many factors that can cause someone to gain weight. Regardless of the cause, obesity is associated with an increased risk of many chronic diseases including cancer, cardiovascular disease, diabetes, hypertension, osteoarthritis, and stroke (2).
Body Fat is An Organ
People often think of body fat as an inert substance that only exists to store extra energy. The truth is that fat stores are far more than just a warehouse for extra energy.
Fat is considered an organ. Body fat creates hormones and actively interacts with our bodies. For example, a hormone called leptin is produced by body fat after eating which helps create a sense of fullness after a meal (3).
How Many Calories Are In a Pound of Body Fat?
In 1958, a scientist named Max Wishnofsky calculated that one pound of body fat contains 3500 calories of stored energy (4).
His calculation was based on the fact that body fat provides about 9 calories per gram. One pound is equal to 484 grams (0.48 kilograms). Therefore one pound of pure fat contains over 4,000 calories.
However, body fat contains more than just pure fat. There are proteins, carbohydrates, and vitamins stored in body fat too. Wishnofsky estimated that fat cells contain about 87% pure fat which is how he arrived at 3500 calories per lb.
More recent research has shown that the composition of fat cells can vary and no one is certain of the exact number of calories in one pound of fat.
While this calculation was intended to be for scientific purposes, this number was quickly adopted by dietitians and others in the nutrition community and is now often cited as fact when discussing weight management. Over time this has led to the creation of the 3,500 calorie rule.
The 3,500-Calorie Rule
Early on, professionals realized that dividing 3500 calories by the number of days in a week provides a nice round number of 500 calories per day.
In other words, forcing your body to burn 500 calories from fat every day by creating an energy deficit should lead you to burn 3500 extra calories per week, and as a result, lose one pound of fat.
Unfortunately, as we will see, and as many dieters well know, achieving and maintaining a weight loss is not always so easy.
Calorie Deficit and Weight Loss
It’s undisputed that creating a calorie deficit is the key to weight loss (5), and that how much weight you lose will depend on how large of a daily deficit you can create.
However, the 3500 calorie rule does not account for the change in metabolic rate seen with weight loss.
As we start to lose weight, our body composition begins to change and our metabolic rate slows down. Eventually, metabolism slows down enough to match that new lower level of caloric intake and you reach the dreaded weight loss plateau.
If you truly want to lose a significant amount of weight and keep it off long term, here is what you need to know.
How Do I Calculate How Many Calories I Need to Lose Weight?
A great starting place is to use an online calculator such as this one to help estimate your calorie needs for your current weight.
If you have a weight loss goal, simply enter your goal weight and in how many weeks you would like to get there. The calculator will give you a target number of calories to aim for each day.
How Many Calories a Day Do I Burn?
Once you calculate how many calories you need using an online calculator, the best way to determine how much your body burns is by doing a calorie count using a food journal. A dietitian can also help you get this process started.
Begin tracking the foods you eat and drink for a period of two to three days. If possible, measure portions, weigh foods and read nutrition labels.
This will give you an accurate measurement of the number of calories you eat each day. If your current weight has been stable for the past three to six months you have been achieving an energy balance.
This means the number of calories you eat each day has been equal to the number you burn.
The number you calculate from tracking your daily calories should help to show if the online calculator is accurate. It also gives a great starting point for a weight loss diet.
How Long Does It Take to Lose 1 LB of Fat?
Unfortunately, there is no perfect formula to answer this question.
What we do understand is that when you first begin a diet and create a calorie deficit much of the initial weight change is due to a loss of water weight.
With continued attention toward creating a caloric deficit and following a low-calorie diet, you will continue to lose body weight.
A healthy rate of weight loss is considered anywhere from 0.5 to 2.0 lbs per week.
At this rate, it is safe to say it should take the average person about one to two weeks to lose one pound of body fat.
How to Achieve a Calorie Deficit
There are only two ways to create a calorie deficit. Burn more calories through new physical activity or make changes to your diet to eat fewer calories.
Burn More Calories
The best way to burn more calories is by establishing a consistent workout routine.
Cardio exercises are great because they burn more calories. One study found that doing cardio exercises five days per week was enough to help participants achieve meaningful weight change (6).
Another approach is to do strength training exercises at least one to two days per week. Weight loss is often accompanied by a loss of lean tissue. Losing muscle tissue lowers how much energy your body needs on a day to day basis.
Regular strength training non only counters the loss of lean tissue, it encourages muscle growth. Seek to increase your activity level so you are doing a combination of strength building exercise and cardio exercise at least five days per week.
This helps create a healthy weight loss resulting from fat loss and not a change in muscle mass (7).
Eat Fewer Calories
Increasing the amount of physical activity you do in a week is an important step to take if you want to achieve and maintain your goal weight. However, if you do not improve the quality of your diet by making small changes to the foods you choose you may end up seeing weight gain as you build new muscle mass.
Change the amount of food you eat with each meal can seem like an easy first step. However, it’s better if you change the quality of the foods you eat, not the quantity. The goal should be to select foods that support a healthier lifestyle.
Aim to create enough of a calorie deficit so you lose about one pound of weight per week. For most people, a 1500-2000 calorie diet with lots of non-starchy vegetables, brightly colored fruits, whole grains, lean proteins, nuts, and healthy fats should be enough to help the average person lose weight.
If you are not seeing results decrease your daily calorie intake by another 100-200 calories or add another day of exercise.
Drawbacks of Counting Calories
Counting calories can be difficult for many people to maintain long term. Sometimes people fixate so much on counting calories they forget to start eating healthier foods. The goal of following a low-calorie diet is not just to lose weight but also to start to see other improvements in your health.
It is also important to make sure you eat enough calories each day. Generally, this is considered to be around 1000 calories per day for women and 1200 calories per day for men.
Eating less than this amount can put your body into starvation mode where it begins to store away everything you eat as fat. This can make it very difficult to lose weight. Be sure to eat enough calories each day to stay above this range.
What Else to Consider When Trying to Lose Weight
There is more to losing weight than just counting calories. One area to focus on is to notice how fast you are eating your meals.
You may have heard that it takes 20 minutes for your stomach to tell your brain that you are full. This is true, and if you eat your meals in under 20 minutes your brain never has time to receive that message. it’s been proven that eating a meal more slowly leads you to eat less (8).
A good way to break the habit of fast eating is to practice mindfulness when eating meals and snacks. Eat at the table, not in front of the television or your car. Put down the fork between each bite and avoid the temptation to look at your phone.
Anything that distracts you while you eat can cause you to eat too quickly.
Losing weight as an adult is a difficult but not impossible task. The key is to find a way to create a calorie deficit by making small changes to the foods you eat and increasing your level of physical activity.
Creating a calorie deficit forces your body to rely upon stored energy to make up the difference. However, a critical point to remember is we want to force our body to pull those extra calories from body fat and not from muscle mass.
Losing muscle mass slows down our basal metabolic rate and makes it difficult to lose weight. This is often what leads to the dreaded weight loss plateau.
Instead of focusing on the number of calories stored in one pound of fat, make sustainable changes to your diet to include more healthy, low-calorie nutrient-dense foods.
Eat when you are hungry, stop when you are full and make the majority of your food choices be as healthy as possible. Work with a dietitian if you need help developing a long term plan.
These are the keys to achieving lasting and sustainable weight loss.
- Hall, Kevin D., and Scott Kahan. “Maintenance of Lost Weight and Long-Term Management of Obesity.” Medical Clinics of North America, vol. 102, no. 1, 2018, pp. 183–97. Crossref, doi:10.1016/j.mcna.2017.08.012.
- Smith, Kristy Breuhl, and Michael Seth Smith. “Obesity Statistics.” Primary Care: Clinics in Office Practice, vol. 43, no. 1, 2016, pp. 121–35. Crossref, doi:10.1016/j.pop.2015.10.001.
- Münzberg, Heike, et al. “Recent Advances in Understanding the Role of Leptin in Energy Homeostasis.” F1000Research, vol. 9, 2020, p. 451. Crossref, doi:10.12688/f1000research.24260.1.
- WISHNOFSKY, MAX. “Caloric Equivalents of Gained or Lost Weight.” The American Journal of Clinical Nutrition, vol. 6, no. 5, 1958, pp. 542–46. Crossref, doi:10.1093/ajcn/6.5.542.
- Westerterp, Klaas R. “Physical Activity, Food Intake, and Body Weight Regulation: Insights from Doubly Labeled Water Studies.” Nutrition Reviews, vol. 68, no. 3, 2010, pp. 148–54. Crossref, doi:10.1111/j.1753-4887.2010.00270.x.
- “Aerobic Exercise Alone Results in Clinically Significant Weight Loss for Men and Women: Midwest Exercise Trial 2.” Obesity, vol. 21, no. 3, 2013, pp. E219–28. Crossref, doi:10.1002/oby.20145.
- Willis, Leslie H., et al. “Effects of Aerobic and/or Resistance Training on Body Mass and Fat Mass in Overweight or Obese Adults.” Journal of Applied Physiology, vol. 113, no. 12, 2012, pp. 1831–37. Crossref, doi:10.1152/japplphysiol.01370.2011.
- Andrade, Ana M., et al. “Eating Slowly Led to Decreases in Energy Intake within Meals in Healthy Women.” Journal of the American Dietetic Association, vol. 108, no. 7, 2008, pp. 1186–91. Crossref, doi:10.1016/j.jada.2008.04.026.