A calorie deficit is a fundamental part of every diet and weight loss process. But even though you’re eating less, it doesn’t mean you are going to lose fat tissue. With an inadequate diet, large caloric restrictions, and incomplete training sessions, you will lose weight in an unhealthy way, which is usually not as sustainable. Let’s see what a caloric deficit is and how it will help you lose body fat!
What Is a Calorie Deficit?
A calorie deficit takes place when you consume fewer calories than your body needs to keep its current weight. Due to this imbalance, the body uses stored energy, often from fat, to make up that difference, which results in weight loss over time.
A calorie deficit is the bedrock of weight loss, and it involves complex physiological processes. But, before understanding what calorie deficit does to your body, you must understand all the basics of caloric balance.
Energy Balance
Your body requires a certain amount of energy – calories throughout the day to maintain its current weight. That number is known as Total Daily Energy Expenditure (TDEE), and it varies for each individual. It depends on sex, age, job, mobility, stress level…
When you want to determine your TDEE, you need to consider three things:
- Basal Metabolic Rate (BMR): This is the energy your body asks for at rest to maintain vital functions like breathing, circulation, and heart pumping.
- Physical Activity: Any movement is important here, whether it is an intentional workout or any non-exercise activity like walking, cleaning, or cooking.
- Thermic Effect of Food (TEF): TEF is the energy your body demands to digest, absorb, and process all the nutrients from food. Different ingredients have different TEF levels, with proteins having the highest one. This means they require more energy for these processes than carbs, for example, and spend more calories doing so.
How to Create a Calorie Deficit?
As said above, to create a calorie deficit, you need to eat fewer calories than your TDEE. But, before you start anything, you have to determine your caloric needs by calculating BMR and TDEE.
Calculating Basal Metabolic Rate (BMR): You can do this in several ways, but two following equations are most popular:
For Males:
BMR = 66.473 + 13.7516 x weight in kg + 5.033 x height in cm9 – 86.7550 x age in years
For Females:
BMR = 655.0955 + 9.5634 x weight in kg + 1.8496 x height in cm – 4.6756 x age in years
For Males:
BMR = 10 x weight in kg + 6.25 x height in cm – 5 x age in years + 5
For Females:
BMR = 10 x weight in kg + 6.25 x height in cm – 5 x age in years – 161
Determining Activity Level: To calculate your activity level, multiply your BMR by an activity factor that reflects your daily activity level:
- Sedentary (little to no exercise): BMR x 1.2
- Lightly Active (simple exercise or sports 1-3 days a week): BMR x 1.375
- Relatively Active (average exercise or sports 3-5 days a week): BMR x 1.55
- Very Active (challenging exercise or sports 6-7 days a week): BMR x 1.725
- Super Active (very tough exercise or sports and physical job): BMR x 1.9
Calculating Total Daily Energy Expenditure (TDEE): This is the total number of calories you burn in a day, including all the activities and bodily functions:
TDEE = BMR x Activity Factor
Practical Advice
Of course, you don’t have to do these calculations by hand, as there are numerous calculators online that will do everything for you. However, it is essential to understand what these numbers mean for your organism. Here is an example calculation:
A 27-year-old woman who weighs 88 kg, is 175 cm tall and is moderately active.
- Calculate BMR (using the Mifflin-St Jeor equation):
BMR = (10 x 88) + (6.25 x 175) – (5 x 27) – 161
BMR = 880 + 1.094 – 135 – 161
BMR ≈ 1.678 calories a day
- Determine your activity level – moderately active:
BMR x 1.55
- Calculate TDEE:
TDEE = 1.678 x 1.55
TDEE ≈ 2.600 calories a day
This means the woman needs approximately 2.600 calories per day to maintain her current weight. But, to lose weight, she needs to create a caloric deficit. A safe and sustainable deficit is typically between 500 to 1000 calories per day. This deficit leads to a weight loss of about 0.5 to 1 kilogram per week.
So, if the girl from the example (2.600 calories a day) wants to eat in 500 calories deficit, that would mean eating 2.100 calories a day.
It is important to note that these equations are estimated only, as each individual is special. The results will vary because of muscle mass, genetic factors, hormonal levels, or health issues, as they all affect actual caloric needs.
To avoid any stagnation, regularly track your calorie intake and expenditure. That way, you will be able to alter your caloric intake grounded on your progress and how your body actually responds to new eating habits. If you hit a plateau, you will probably need to re-evaluate both caloric intake and activity level.
Also, it is super important to focus on nutrient-dense foods to meet your caloric needs. Establish you’re getting a balanced intake of macronutrients (carbohydrates, proteins, fats) and micronutrients (minerals and vitamins).
When you eat in a caloric deficit, you will lose weight even if you’re eating highly processed carbohydrates (such as fast food and sugar), but you won’t lose fat. Foods like those are packed with calories, so this means you must eat very small portions to meet that calorie deficit. You will make your body starve and use up muscles for energy while leaving your body soft and without energy.
That’s why it is crucial to eat diverse and nutritional meals, especially enough proteins. The right diet in caloric deficit will make your body burn fat fast and effectivly, but still stay highly energized and healthy.
How Does Your Body Respond to Caloric Deficit?
The body will respond differently to caloric deficit in different stages; let’s see how!
Immediate Response
In the moment of caloric deficit, the body uses glycogen sources in the liver and muscle to provide glucose for energy. Glycogen is actually a form of stored carbohydrate, so when it breaks down, it releases glucose into the bloodstream. Thus, when caloric deficit occurs, the body’s immediate response is initial weight loss, but a lot of that weight is water, as every gram of glycogen goes together with 3 grams of water.
After some time, as glycogen stores deplete, the body boosts the degradation of stored fat into free fatty acids and glycerol, so it can use it for energy. This process is popular as lipolysis because it occurs in fat tissue. It releases fatty acids directly into the bloodstream for metabolic processes, but especially muscles.
Metabolic Adaptations
Prolonged calorie deficit results in decreased BMR because the body adapts and attempts to preserve energy. This is a true phenomenon known as adaptive thermogenesis. What’s more, at this moment, thyroid hormone (T3 especially) levels decrease, slowing down metabolism.
Hormonal changes are huge in this stadium, as well. Because fat cells produce leptin, its levels drop with fat loss. Lower leptin levels minimize energy spending and increase hunger, so you may feel like you can eat A LOT. Next is the “hunger hormone” ghrelin, whose levels skyrocket during a caloric deficit, stimulating appetite and making you hungry all the time.
On the other side, the body becomes more sensitive to insulin as there is less fat and carbohydrates to deal with. Take into consideration that cortisol (stress hormone) levels will probably increase, especially if caloric deficit is large or accompanied by high levels of physical activity.
Shift in Energy
Ensure that your diet is enriched with protein, as the calorie deficit (especially large and prolonged) will make your organism use fat stores for energy. Otherwise, it will break down the muscles. The body will become super efficient at burning fat, too, as it is the main fuel for all metabolic processes.
Long-Term Adaptations
It is not rare that people unconsciously reduce their spontaneous physical activities, such as standing or walking, when in a caloric deficit. This counteracts some of the expected weight loss. As said above, weight loss plateaus are usual as the body adapts to a new lower energy intake, causing the rate of weight loss to slow or stop.
How to Optimize Caloric Deficit?
Gradual Reduction: Start slow, as moderate and gradual (e.g. 500 calories per day) calorie deficit is only sustainable option.It is less likely to trigger severe metabolic adaptations and binge eating.
Choose Food Wisely: Opt for high-nutrient, but low-calorie foods which have big volume, like salad, kale, or cabbage. Include loads of vegetables, fruits, lean proteins, and whole grain to keep nutrient intake and satiety.
Exercise: Cardiovascular and resistance training duo is the best recipe to enhance fat loss while preserving muscle mass and metabolic rate.
Regular Monitoring: Keeping an eye on progress is critical, as people usually need to adjust their calorie intake and spending to overcome plateaus and ensure a healthy weight loss process.
image sources
- Roman: CrossFit Inc
