What is a calorie deficit?
Simple, easy-to-understand definition
It is surprising that many people start their weight loss journey but still do not understand the core concept – “calorie deficit”. Simply put, this is a state where the body consumes more calories than it takes in through eating. At that time, the body does not have enough energy from food and is forced to use reserves (excess fat) to compensate, thereby helping to lose weight.
Why is a calorie deficit needed to lose weight?
Effective weight loss always starts with creating a calorie deficit – meaning the amount of calories you take in is less than the amount of calories your body consumes. The human body only starts burning excess fat when it is lacking energy. This is a natural principle: when the calories you take in are not enough to maintain life activities, the body is forced to use stored fat as fuel.
No matter how healthy you eat, if the total calorie intake is still higher than the needs, weight loss is impossible. For example, you can drink a detox smoothie every day, but if you still consume a total of 2,500 calories while your body only needs 2,000 calories, you will not burn fat. On the other hand, if you create a suitable calorie deficit, fat loss will occur naturally and safely.
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Let’s say your body needs about 2,000 calories a day to maintain its activities (TDEE – Total Daily Energy Expenditure). If you take in 1,600 calories, that means you are creating a 400-calorie deficit every day. After a week, you will have accumulated a deficit of about 2,800 calories. Since 0.45 kg of fat is equivalent to about 3,500 calories, you can lose 0.45 kg in about 1-1.5 weeks if you maintain that deficit regularly.
However, it is important not to cut calories too much. Eating less than 1,200 calories/day (for women) or 1,500 calories/day (for men) can cause fatigue, muscle loss, and negatively affect metabolism. Safe fat loss requires a combination of a healthy diet and reasonable exercise to preserve muscle mass and support effective metabolism.
Calorie Deficit – The “Golden Key” of all weight loss methods
No matter what diet you apply – from Low Carb, Keto, Eat Clean to Intermittent Fasting – the decisive factor for success is still a calorie deficit. For example, the low-carb or Keto diet helps you reduce starch so that the body is forced to use fat for energy. But if you consume too much fat or protein, the total calories will still be excess, and you will not lose weight. Similarly, Intermittent Fasting (IF) is only effective if you control your calorie intake during mealtimes. Eating healthy, like Eat Clean, won’t help if you’re still overeating.
Therefore, it can be said that any diet is just a tool to help create a calorie deficit more easily. Without achieving a calorie deficit, weight loss will not be possible.
How to create a safe and effective calorie deficit?
Losing weight doesn’t mean fasting or cutting calories to the extreme. A safe calorie deficit requires a balance between nutrition, exercise and perseverance. First, you need to calculate your TDEE (Total Daily Energy Expenditure), including basal calories consumed at rest (BMR), calories from exercise and calories consumed to digest food (TEF). You can use the Harris-Benedict or Mifflin-St. Jeor’s formula to calculate BMR, then multiply by the exercise factor to get TDEE. For example, a 30-year-old woman, 160cm tall, weighing 60kg, exercising 3–4 times a week, may have a TDEE of around 2,000 calories.
Once you have your TDEE, cut back gently by 300–500 calories/day to lose 0.3–0.5kg/week – a healthy and safe rate. Don’t eat less than 1,200 calories/day for women and 1,500 calories/day for men. Prioritise protein-rich foods like lean meat, eggs, fish, and high-fibre vegetables to stay full longer. Avoid skipping breakfast or drinking sugary drinks, and replace them with water or unsweetened tea.
At the same time, increase energy expenditure through exercise. Cardio helps burn fat quickly, while weight training helps maintain muscle mass, which is extremely important to avoid muscle loss when losing weight. Daily activities like walking, climbing stairs, and cleaning the house also increase expenditure (NEAT). For example, if you eat 1,700 calories and burn an additional 300 calories through exercise, you have created a 600-calorie deficit/day.
Harmful misconceptions about calorie deficit
Some common misconceptions about weight loss cause many people to fail or affect their health. First, many people think that the more they fast, the faster they will lose weight. In fact, eating too little will cause the body to fall into survival mode, slowing down metabolism and causing you to lose muscle. Instead, reduce calories slowly and eat enough nutrients.
Second, many people believe that you only need to exercise heavily without dieting. Meanwhile, diet accounts for 70% of weight loss results. You can exercise hard, but if you eat more than you burn, you will still fail to lose weight.
Third, lemon water or detox does not have a miraculous effect on burning fat. They may help you feel lighter or temporarily reduce your appetite, but they are no substitute for controlling your energy intake and output. Drinking detox instead of rice can leave your body lacking nutrients, tired and prone to overeating later.
What is a calorie deficit? The golden principle to help you lose weight scientifically and sustainably
How to maintain a calorie deficit long-term without exhaustion
The key to sustainable weight loss is to maintain a calorie deficit scientifically and long-term. First of all, you don’t need to be too strict. Keep a relaxed mindset, allow yourself to eat “comfortably” 1-2 meals a week and don’t blame yourself if you eat more than planned. Getting enough sleep helps control hunger hormones, stabilise your psychology and prevent emotional eating.
Next, don’t rely on dieting or exercise alone. Eating healthy combined with regular exercise will help you retain muscle, increase metabolism and burn fat more effectively. A 60kg person eating 1,500 calories/day and walking 30 minutes a day can create a 300-400 calorie deficit – enough to lose fat safely.
Finally, persevere for at least 4-6 weeks before evaluating the results. Losing weight is a long journey; it cannot be “speedy” in a few days. The first week, you may lose weight quickly due to dehydration, but then the rate of loss will slow down – that is completely normal. Weigh yourself once a week, take pictures of your body, and track your waistline to see the changes clearly.
Summary
Losing weight properly starts with understanding and applying a scientific calorie deficit. Instead of applying extreme measures, combine reasonable nutrition, regular exercise and adequate rest. Don’t turn weight loss into a battle, but see it as a journey to take care of your body and improve your quality of life. Patience, perseverance, and listening to your body are the keys to your long-term success.