At the core of weight loss lies a single principle: consuming fewer calories than your body burns. This principle is called a calorie deficit. It sounds simple, but in practice, many people do not understand why it does not work for them. That is because they skip one critical step: finding the right starting point.
First, you need to understand two concepts: BMR and TDEE.
BMR, or Basal Metabolic Rate, is the number of calories your body needs while doing absolutely nothing, just to keep breathing, keep your heart beating, and keep your organs functioning. Even if you never got out of bed, your body would still use this much energy.
TDEE, or Total Daily Energy Expenditure, is the actual number you reach by adding your daily activity on top of this. Walking, work, exercise, and even digesting food are included in this calculation. TDEE is your "maintenance calories"; if you eat this amount every day, you maintain your weight.
The difference between BMR and TDEE is critical. If you want to lose weight, your target should be below your TDEE, but you should not go below your BMR. This threshold is the minimum amount your body needs for its basic functions.
How is a calorie deficit calculated?
Let's go step by step:
- Calculate your BMR. It varies depending on your age, sex, height, and weight. Lettuce calculates this automatically for you.
- Find your TDEE based on your activity level. If you live a sedentary lifestyle, multipliers such as BMR x 1.2 are used; if you are moderately active, BMR x 1.55 may be used.
- Set a target below your TDEE. A moderate daily deficit of 300 to 500 calories can result in approximately 0.5% to 1% fat loss per week, without experiencing the negative effects of excessive restriction.
Let's make this more concrete:
Example male profile: 30 years old, 178 cm tall, weighs 85 kg, and works in an office. He goes for walks 2 to 3 times per week. His BMR is approximately 1,900 calories. With a lightly active lifestyle multiplier of 1.375, his TDEE reaches around 2,600 calories. With a deficit of 400 to 500 calories, his daily target becomes 2,100 to 2,200 calories. At this pace, approximately 0.5 kg of fat loss per week may be expected.
Example female profile: 165 cm tall, weighs 65 kg, and similarly works a desk job. She does Pilates several times a week. Her BMR is approximately 1,480 calories. With the same activity multiplier, her TDEE reaches around 2,035 calories. With a deficit of 350 to 400 calories, her daily target becomes 1,600 to 1,700 calories. To achieve the same weekly progress target, she has to work within a narrower range compared with Ahmet; therefore, for women, the quality of macronutrients may be more important than calorie counting alone.
Is too large a deficit bad?
Yes. Losing more than 1% of your body weight per week increases the risk of muscle loss. Following a diet for a long period of time may also reduce your TDEE by 10% to 15% more than mathematical calculations predict, which can trigger a condition known as "metabolic adaptation." In other words, going too fast often leads to slower results.
The numbers change
Your TDEE should be recalculated after every 10 to 15 kg of weight change, because as you lose weight, your BMR also decreases. Lettuce's weight tracking feature makes it easier to monitor this change and keep your goals up to date.
The information in this article is for general informational purposes and does not constitute medical advice. We recommend consulting a dietitian or healthcare professional to personalize your nutrition plan.