Calorie Deficit — How to Lose Weight Safely

Want to lose weight? There is one fundamental rule: you need to eat fewer calories than your body burns. This is called a calorie deficit, and it is the only mechanism that leads to weight loss — regardless of which diet you follow. A good calorie tracker app can make it easier to stay on top of your intake.

But how large should your deficit be? And how do you do it without feeling hungry all the time? Use our free calorie intake calculator to estimate your daily calorie needs. Here is everything you need to know.

What is a calorie deficit?

A calorie deficit occurs when you eat fewer calories than your body uses throughout the day. Your body needs energy for everything — from breathing and digesting food, to walking, exercising, and thinking. This total energy use is called your TDEE (Total Daily Energy Expenditure).

When you eat less than your TDEE, your body must draw the missing energy from its reserves — primarily fat stores. Over time, this leads to weight loss.

Example: If your TDEE is 2200 kcal and you eat 1700 kcal per day, you have a deficit of 500 kcal. Over a week, that adds up to 3500 kcal, which equals roughly 0.5 kg (about 1 lb) of fat loss.

According to the Norwegian Directorate of Health dietary guidelines, weight loss should happen gradually — 0.5 to 1 kg per week is considered safe and sustainable.

How large should your calorie deficit be?

Most experts recommend a moderate deficit:

• Small deficit (250 kcal/day): Slow weight loss, easier to maintain, less muscle loss. Approximately 0.25 kg per week.
• Moderate deficit (500 kcal/day): Recommended for most people. Approximately 0.5 kg per week. Good balance between results and sustainability.
• Large deficit (750–1000 kcal/day): Faster results, but harder to sustain. Greater risk of muscle loss, fatigue, and nutrient deficiencies. Should only be done under professional supervision.

Rule of thumb: A deficit of 500 kcal per day results in roughly 0.5 kg of weight loss per week. This is safe and sustainable for most people.

Minimum calorie intake

Regardless of how large your deficit is, you should not eat below:

• 1500 kcal/day for men
• 1200 kcal/day for women

Below these levels, it becomes difficult to get enough nutrients, and the risk of muscle loss, hormonal issues, and other health problems increases. These recommendations are in line with NIH guidelines for weight management.

How to calculate your calorie needs

To create a calorie deficit, you first need to know how many calories your body uses. Here are the steps:

Step 1: Calculate your Basal Metabolic Rate (BMR)

BMR is the energy your body uses at complete rest — for breathing, pumping blood, and maintaining organs (learn more about BMR). The most commonly used formula is Mifflin-St Jeor:

• Men: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age + 5
• Women: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age - 161

Step 2: Multiply by your activity factor

Multiply your BMR by a factor based on how active you are:

Result = your TDEE (Total Daily Energy Expenditure).

Step 3: Subtract the deficit

Subtract 500 kcal from your TDEE for a moderate deficit:

Calorie intake for weight loss = TDEE - 500

Example: A 30-year-old man weighing 80 kg and 180 cm tall who exercises 3 times per week:

• BMR = 10 x 80 + 6.25 x 180 - 5 x 30 + 5 = 1780 kcal
• TDEE = 1780 x 1.55 = 2759 kcal
• Recommended intake = 2759 - 500 = 2259 kcal/day

Tips for sticking to a calorie deficit

1. Eat high-protein meals

Protein keeps you fuller than carbohydrates and fat, and it protects your muscle mass during weight loss. Aim for at least 1.6 g of protein per kg of body weight.

Good protein sources:

• Chicken and turkey
• Fish and seafood
• Eggs
• Greek yoghurt and Skyr
• Beans and lentils
• Cottage cheese

2. Eat plenty of vegetables

Vegetables are low in calories but high in volume. Fill half your plate with vegetables to stay full without blowing your calorie budget.

3. Avoid liquid calories

Soda, juice, alcohol, and fancy coffees can contain hundreds of calories without filling you up. Drink water, coffee (without sugar), and tea instead.

4. Plan your meals

Impulsive food choices often lead to higher calorie intake. Plan what you will eat in advance and keep healthy options available.

5. Use a calorie tracker app

Tracking your food intake gives you an overview and reveals "hidden" calories you might not think about. Harvard Health recommends calorie counting as an effective tool for weight management. An app like Kalori makes it easy — just take a photo of your food.

Track your food intake easily: The Kalori app lets you take a photo of your food — AI calculates the calories automatically. Download for free.

Check if your weight is in the normal range with our BMI calculator.

Common mistakes

Going too aggressive

A deficit that is too large may feel effective at first, but often leads to:

• Muscle loss
• Extreme hunger and binge eating
• Low energy and poor mood
• Hormonal disruptions
• The "yo-yo effect" — rapid weight regain afterwards

Start with a moderate deficit and be patient.

Not tracking your food intake

Most people underestimate how much they eat by 20–50%. Without measuring or tracking, it is easy to believe you are in a deficit when you actually are not.

Ignoring protein

Without enough protein, your body loses more muscle mass and less fat. Make sure a good portion of your calories comes from protein.

Giving up too early

Weight naturally fluctuates from day to day — fluid, digestion, and hormones all affect your weight. Look at the trend over weeks, not individual days. Give it at least 4 weeks before considering adjustments.

Frequently asked questions

How long does it take to lose 5 kg?

With a deficit of 500 kcal per day, you can expect to lose about 0.5 kg per week. That means 5 kg takes roughly 10 weeks. The rate varies from person to person.

Do I need to exercise to lose weight?

No, a calorie deficit alone is enough. But exercise — especially strength training — helps preserve muscle mass, increases your calorie burn, and is good for your overall health.

What do I do if my weight loss stalls?

Weight plateaus are normal. Your body adapts over time. Try to:

1. Verify that you are actually in a deficit (tracking errors may have crept in)
2. Slightly increase your activity level
3. Reduce your calorie intake by an additional 100–200 kcal
4. Be patient — plateaus rarely last more than 2–3 weeks

Is it dangerous to eat too little?

Yes, prolonged severe calorie restriction can lead to nutrient deficiencies, muscle loss, hormonal problems, osteoporosis, and a weakened immune system. Stick to the recommended minimum levels and consult your doctor if in doubt.

Can I lose weight without a calorie deficit?

No. Regardless of which diet you follow — low-carb, keto, intermittent fasting, or anything else — weight loss is always the result of eating fewer calories than you burn. Different diets are simply different strategies for achieving a calorie deficit. Without a deficit, you will not lose weight.

Is a calorie deficit safe for everyone?

A calorie deficit is not recommended for everyone. Pregnant and breastfeeding women, growing children and teenagers, and people with eating disorders or a history of them should not restrict calories without guidance from a healthcare professional. According to the Norwegian Directorate of Health, these groups have increased nutritional needs, and restrictive diets can be harmful. Always talk to your doctor if you are unsure.