Weight loss has one scientific basis: over time, eating fewer calories than you burn. That is a calorie deficit. Here is what it is, how to calculate it and where the safe line sits.
What is a calorie deficit?
Your body burns energy for everything from breathing to walking. Eat less than you burn and the difference is covered by your fat stores, so you lose weight. Eat more and the stores grow. A calorie deficit is simply eating less than you burn.
How to calculate your daily needs
First estimate your basal metabolic rate (the energy you burn at rest), then multiply by your activity level to get your total daily burn:
- Sedentary (desk job): BMR × 1.2
- Lightly active (1-3 days): BMR × 1.375
- Moderately active (3-5 days): BMR × 1.55
- Very active (6-7 days): BMR × 1.725
Eat below that total and you are in a deficit. If you burn 2200 and eat 1800, that is a 400-calorie daily deficit.
What deficit is safe?
A general rule is 15-25% below your daily burn, which is about 0.3-0.7 kg per week for most people. An extreme deficit looks fast but costs muscle, causes fatigue and makes the weight come back. "As low as possible" is not the goal.
Three ways to create the deficit
- Eat less (smaller portions, less sugar and processed food).
- Move more (walking, daily steps, exercise).
- Both together - the most sustainable.
The 5 most common mistakes
- Not counting drinks. Juice, sugary coffee and alcohol close the deficit unnoticed.
- Too aggressive a deficit. Under 1000 calories slows the metabolism.
- Too little protein. You lose muscle in a deficit.
- Weekend blow-outs. They can cancel a whole week's deficit.
- Judging by the daily scale. Water moves weight; watch the weekly average.
How Diet Prof sets your deficit
The free body analysis calculates your daily need and, if you want to lose weight, the programme sets a healthy deficit automatically - so you do not wrestle alone with "how much should I eat". Your list is built to that target, and as you lose weight it recalculates, which is the key to breaking plateaus. See How Does Diet Prof Work?
Frequently asked questions
Do I have to count calories forever?
Understanding the logic matters, but you need not count every bite. A list already built to your target does the maths for you.
Can I do it with diet alone, no exercise?
Yes; the deficit comes mainly from food. Movement helps and protects muscle.
Why did my weight loss stop?
As you lose weight your body burns less, so the old deficit is no longer a deficit. The fix is to recalculate for your current weight.
