What to Know About Calories and Body Fat in 2021
Relative to food and the body, calories are units of energy that allow the body to function. Food provides this energy, some of which the body stores and some of which it uses. As the body breaks down food, it releases calories as energy.
Max Wishnofsky first propagated the concept that there are approximately 3,500 calories in a pound (lb) of body fat.
Simply put, to lose 1 pound of body fat per week, people will need a deficit of around 500 calories per day. They can achieve this by consuming approximately 500 calories less than they currently are, burning an additional 500 calories per day with exercise, or a combination of the two.
If the body consumes too many calories or burns too little, weight gain occurs. This is because the body stores calories that it does not use as body fat. Organs including the brain, heart, lungs, liver, and kidneys account for about 80% of total daily energy use.
Recent research calls into question this rule, concluding that it overestimates someone’s weight loss potential. The rule does not take into account dynamic changes in metabolism, hunger, and satiety levels as weight loss occur.
The National Institutes of Health have developed a more precise new rule of thumb: Every 10 calorie decrease per day leads to a final 1 pound loss. Only time will tell how long it takes to lose weight, so patience and consistency are key.
How fat works
Body fat, or adipose tissue, consists of adipocytes.
These are fat cells and are produced along with other types of cells and proteins. Fat cells contain lipids, including cholesterol and triglycerides.
Fat tissue stores energy for the body to use and protects organs. It also releases hormones that control many functions in the body, such as insulin sensitivity and appetite.
People with more body fat can experience something called leptin resistance, in which the body is less sensitive to the satiety hormone leptin. This, in turn, increases hunger and food intake, making it difficult to maintain weight over time.
There are two types of adipose tissue: white and brown. Brown adipose tissue is more metabolically active. Burns more calories and helps control weight, insulin sensitivity, and general health to a greater extent than white adipose tissue.
If people have excess body fat, their white adipose tissue is more likely to have expanded.
Having too much body fat can cause obesity and cause many health problems, such as diabetes, high blood pressure, and heart disease. Having too little body fat can also be harmful and lead to health problems like malnutrition and fertility problems.
How do calories work?
Research estimates that muscle burns calories at a rate of 10 to 15 calories per kilogram (kcal/kg) per day. This equates to 4.5–7 kcal/lb per day.
Muscles account for approximately 20% of total energy expenditure each day. For people with 20% body fat, body fat represents 5% of energy expenditure.
So people with more muscle tissue have a higher metabolic rate. This means that they burn more calories and can maintain their body weight more easily.
How is calories calculated?
The calories in food are not exactly the same amount inside the body as they are outside the body.
That said, scientists measure the amount of caloric energy that food contains by using a device called a bomb calorimeter.
By burning food in this device, scientists can measure the heat released to find out the number of calories in the food.
This provides a figure for the total potential energy of food. However, this is not a true reflection of how the body will use energy from food. The body cannot always use all the calories that people consume.
Calorie losses can occur due to:
Incomplete digestion of food.
Have an ineffective metabolism.
How people burn calories will depend on their metabolism, digestion, and general health and fitness levels.
A calorimetry machine can show how many calories people burn when they rest. This is called your basal metabolic rate. The machine measures carbon dioxide, which is the waste product of food that the body burns for energy. Other accurate methods of estimating calorie expenditure use air or water displacement technology.
With these tools, people can calculate a precise number of calories burned during rest, activity, or exercise. It is important to recheck this number every 3–6 months to understand how body composition and calorie needs change over time.
People can use calorie counting tools and fitness trackers to get a rough idea of how many calories they are consuming and how many they are burning. However, this will not always be completely accurate.
Are the highest or lowest-calorie types of fat different?
One gram (g) of fat contains 9 calories, which is more than double the number of calories in carbohydrates and protein, which contain 4 kcal / g.
However, these are rough estimates, as specific foods affect insulin demand, gut bacteria, and digestion and absorption differently. All of these factors affect the calories per gram of food and an individual’s metabolic rate.
Certain fats are healthier than others. Consuming too much trans and saturated fat can increase the levels of harmful cholesterol in the body and increase the risk of heart disease.
Monounsaturated and polyunsaturated fats are good for the body. Some good sources of these fats include fatty fish, nuts, seeds, and vegetables.
The body needs a certain amount of healthy fat to function properly. Research suggests that while there is no single macronutrient dietary plan that works for everyone due to individual needs, most health experts recommend the following amounts of carbohydrates, proteins, and fats for a balanced diet:
Healthy fats: 20–35% of calories.
Protein: 15-20% of calories.
Complex carbohydrates: the remaining percentage of calories.
How many calories should I eat to lose weight?
If people want to lose 1 to 2 pounds per week, they will need a calorie deficit of 500 to 1,000 calories per day.
People can lose weight by reducing their calorie intake, but it is also important that the calories they eat come from healthy, nutrient-dense foods.
An easy way to reduce your calorie intake and eat a balanced, healthy diet is to swap certain foods for low-calorie options.
For example, eating a sandwich with additional greens and salad instead of additional slices of cheese and ham can reduce your calorie intake by up to 154 calories.
The Heart Association also suggests the following tips as the best choices people can make when cooking:
Use cooking oils that contain less saturated fat, such as olive, avocado, sunflower, or peanut oil.
Use a cooking spray to useless.
If you use canned foods, such as beans, tomatoes, or fish, choose options that do not have added salt or rinse them with water to remove some of the salt.
If you eat canned fruit, choose products that contain juice rather than syrup.
People can also combine a reduction in calorie intake with exercise to burn the calories stored in the body.
Previous research has shown that there are approximately 3,500 calories in 1 pound of body fat. This has led many people to believe that if they want to lose 1 pound of body weight, they only need a 3,500 calorie reduction.
For example, this would mean losing 500 calories each day to lose 1 pound of body fat in a week. Although weight loss and human metabolism are much more complex than this basic calculation, it is clear that a calorie deficit is necessary for weight loss.
However, the amount of time it takes to lose a specific amount of weight varies between people.