Calories are the energy in food.
They fuel everything you do, from sleeping to running a marathon.
Your body can use them to fuel work right away, or store them for later use.
Some calories can be stored as glycogen (carbs), but the majority is stored as body fat.
This article explains how many calories are in a pound of body fat.
It also discusses the 500-calorie deficit myth and presents some tools for predicting realistic weight loss.
Let's take a moment to define what we mean by body fat.
For starters, body fat is not just pure fat.
Pure fat has a very high energy content, or about 9 calories per gram. This amounts to about 4,100 calories per pound of pure fat.
However, body fat is not just pure fat. Body fat consists of fat cells, called adipocytes, which also contain some fluids and proteins in addition to fat.
Therefore, the calorie content of body fat is going to be a bit less than the calorie content of pure fat (, ).
Bottom Line: Body fat is mixed with fluid and protein. Therefore, its composition and calorie content is not the same as pure fat.
In 1958, a scientist named Max Wishnofsky concluded that the caloric equivalent of one pound of body weight lost or gained was 3,500 calories ().
He based his conclusion on the scientific evidence available at the time. Decades later, his result has been cited thousands of times in the media and scientific literature (, , , ).
It's basically become common knowledge that one pound of body fat contains 3,500 calories. But is it really true? Let's attempt to find out.
We will be using generally accepted values for this calculation. However, some research does show slight variations ().
In general, we can :
- One pound equals 454 grams.
- Pure fat contains 8.7–9.5 calories per gram.
- Body fat tissue is 87% fat.
Using those values, we can conclude that a pound of body fat actually contains anywhere from 3,436 to 3,752 calories.
However, it is important to note that these calculations are based on old research.
Some of the studies state that body fat tissue contains only 72% fat. Different types of body fat may also contain varying amounts of fat.
Bottom Line: A pound of body fat may contain anywhere between 3,436 and 3,752 calories, roughly estimated.
It is a common myth that if you eat 500 fewer calories each day, or 3,500 fewer calories a week, you will lose one pound of fat each week.
This would equal a total of 52 pounds in a year.
However, the reality is very different.
The 500-calorie deficit myth significantly overestimates the potential weight loss that can be achieved over a period of time (, , ).
This estimate seems to work fairly well in the short term, for moderate weight loss in overweight and obese people. But it falls apart in the long term, and sets people up for failure and disappointment.
What this myth fails to account for is the body's response to the changes in body composition and diet ().
When you reduce calorie intake, your body responds by making you burn fewer calories. You start moving around less, and the body becomes more efficient. It does the same amount of work, but uses fewer calories than before ().
You may also lose muscle mass along with the fat, which also makes you burn fewer calories.
This is often called starvation mode, although the technical term is "adaptive thermogenesis" ().
Weight loss is not a linear process, and typically slows down over time ().
Bottom Line: The 500-calorie deficit diet overestimates the potential for weight loss. It does not account for changes in body composition and a reduction in calories burned.
Nowadays, there are apps and online tools that may provide a better, more realistic assessment of your predicted weight loss.
, developed by the National Institute of Health, provides calorie levels for both weight loss and maintenance.
It takes into account how diet and exercise contribute to weight loss, as well as how your body responds to reduced calorie intake. It has an immense amount of mathematical calculations behind it ().
Another good tool to predict weight loss is the , developed by the Pennington Biomedical Research Center.
This tool also allows you to calculate weight loss, based on dietary intake and exercise.
Bottom Line: The 500-calorie deficit rule is not a realistic way to predict weight loss. Better tools exist to predict weight loss over a period of time.
When you're trying to lose weight, what you really want to get rid of is body fat — both under the skin and around the organs.
Unfortunately, weight loss doesn't necessarily equal fat loss. One unwelcome side effect of losing weight is the loss of muscle mass ().
The good news is that there are some ways to minimize the loss of muscle mass.
- Lift weights: Studies show that resistance training can be incredibly helpful in preventing the loss of muscle mass when losing weight (, , ).
- Eat plenty of protein: With a high protein intake, your body is much less likely to break down your muscles for energy (, , ).
Both of these strategies are also useful to prevent a reduction in calories burned as you lose weight.
Bottom Line: Weight lifting and high protein intake may help prevent muscle loss for people who are trying to lose weight. They can also help prevent a reduction in the amount of calories you burn.
A pound of body fat may contain anywhere from 3,436 to 3,752 calories.
However, it is a myth that just eating 500 fewer calories per day (3,500 per week) causes weight loss of one pound.
This may work in the short-term, but the body will soon adapt by making you burn fewer calories. For this reason, weight loss slows down over time.