How Many Calories Deficit to Lose 1kg a Week 

Losing weight comes down to one simple truth: you need to burn more calories than you eat. But exactly how many calories do you need to cut to lose 1kg per week? Let’s break down the science and give you a clear plan that actually works.

What’s the Exact Calorie Deficit Needed to Lose 1kg?

You need a deficit of 7,700 calories per week to lose 1kg of body fat. This means cutting 1,100 calories from your daily intake.

Here’s the math: One kilogram of body fat contains roughly 7,700 calories of stored energy. To lose that kilogram in seven days, divide 7,700 by 7, which equals 1,100 calories per day.

This number comes from decades of research on how the human body stores and burns fat. When you create this deficit consistently, your body taps into fat stores for energy, leading to weight loss.

How Do You Create a 1,100 Calorie Daily Deficit?

The most effective approach combines eating less with moving more. Research shows that using both diet and exercise together produces better results than either method alone.

Here’s a practical breakdown:

1. Cut 600-700 calories through diet changes
2. Burn 400-500 calories through exercise
3. Track everything to stay on target

This split works because cutting 1,100 calories from food alone leaves most people too hungry to stick with the plan. Adding exercise means you can eat more food while still hitting your deficit target.

What Does 1,100 Calories Look Like in Real Food?

Understanding how many calories deficit to lose 1kg a week means knowing what you’re actually cutting from your meals. Here are common foods and their calorie counts:

High-calorie foods to reduce:

• Large flat white coffee with full cream milk: 220 calories
• Meat pie from the servo: 450 calories
• Standard serve of hot chips: 350 calories
• Two slices of Vegemite toast with butter: 280 calories
• Can of Coke: 140 calories

Lower-calorie swaps:

• Black coffee or long black: 5 calories
• Grilled chicken breast (150g): 165 calories
• Baked sweet potato: 90 calories
• Two slices of toast with Vegemite (no butter): 180 calories
• Sparkling water: 0 calories

Making just three or four smart swaps per day gets you to that 600-700 calorie reduction without feeling deprived.

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How Much Exercise Burns 400-500 Calories?

Different activities burn calories at different rates. Here’s what 30-45 minutes of exercise looks like for an 80kg person:

1. Running at 10km/hour: 450 calories
2. Swimming laps: 400 calories
3. Cycling at moderate pace: 350 calories
4. Brisk walking: 200 calories
5. Weight training: 250 calories

You don’t need to smash yourself at the gym every day. Pick activities you actually enjoy and can do consistently. A 45-minute walk in the morning plus a 30-minute weights session covers your exercise target.

Is Losing 1kg Per Week Safe for Everyone?

Losing 1kg per week is safe for most people who are overweight or obese. However, this rate isn’t suitable for everyone.

This pace works well if you:

• Have more than 10kg to lose
• Are generally healthy with no medical conditions
• Can maintain good energy levels
• Aren’t losing muscle mass

Slow down if you:

• Feel constantly tired or weak
• Are losing strength in the gym
• Have less than 5kg to lose
• Experience hair loss or other health issues

Research from the University of Melbourne shows that people who lose weight at 0.5-1kg per week are more likely to keep it off long-term compared to those who crash diet.

What Happens If You Cut Calories Too Low?

Dropping below 1,200 calories per day for women or 1,500 for men causes problems. Your body goes into conservation mode, slowing your metabolism to protect itself.

Signs you’ve cut too much:

• Constant hunger and food obsession
• Poor sleep quality
• Feeling cold all the time
• Difficulty concentrating
• Mood swings and irritability

The goal is to eat as much as possible while still losing weight. This keeps your metabolism running strong and makes the process sustainable.

How Do You Track Your Calorie Deficit Accurately?

Tracking doesn’t need to be complicated. Use these three simple methods:

1. Food tracking apps
Apps like MyFitnessPal or Easy Diet Diary (Australian-specific) let you scan barcodes and log meals. Spend five minutes after each meal recording what you ate.

2. Weekly weigh-ins
Step on the scales every Monday morning after using the bathroom but before eating. Track the trend over four weeks, not daily fluctuations.

3. Progress photos
Take front, side, and back photos every two weeks in the same lighting and clothing. Sometimes the scales don’t move but your body composition changes.

What About Weekends and Social Events?

You don’t need to be perfect seven days a week. Research shows that maintaining your deficit five days per week and eating at maintenance on weekends still produces weight loss.

Here’s a realistic weekly plan:

• Monday to Friday: 1,100 calorie deficit (5,500 total)
• Saturday: Maintenance calories (no deficit)
• Sunday: 500 calorie deficit

This gives you 6,000 calories of deficit per week, which equals about 0.8kg of fat loss. You still get to enjoy weekend brunches and dinners with mates without derailing your progress.

How Long Until You See Results?

Most people notice changes within two weeks of consistent effort. Your clothes fit differently first, then the scales start moving.

Week 1-2: Less bloating, more energy, clothes feel looser
Week 3-4: Clear weight loss on scales, others start noticing
Week 5-8: Significant visible changes, need smaller clothes
Week 9-12: Major transformation, new habits feel normal

The key is consistency. Missing one day doesn’t matter. Missing one week starts to show. Missing one month means starting over.

Should You Adjust Your Deficit as You Lose Weight?

Yes. As you get lighter, your body needs fewer calories to function. Every 5-10kg lost means recalculating your deficit.

A person weighing 100kg burns more calories just existing than someone weighing 80kg. If you don’t adjust, your weight loss will slow down or stop completely.

Recalculate your calorie needs every month using an online calculator or by visiting a dietitian. Most people need to reduce their intake by 50-100 calories for every 5kg lost.

What’s the Role of Protein in Weight Loss?

Protein is your best friend when losing weight. It keeps you full, protects your muscle mass, and actually burns calories during digestion.

Aim for 1.6-2.2 grams of protein per kilogram of body weight. For an 80kg person, that’s 128-176 grams daily.

High-protein foods:

1. Chicken breast: 31g protein per 100g
2. Greek yoghurt: 10g protein per 100g
3. Eggs: 6g protein per egg
4. Tuna: 26g protein per 100g
5. Lentils: 9g protein per 100g

Getting enough protein means you lose fat, not muscle. This keeps your metabolism high and helps you look toned, not just smaller.

Can You Speed Up Fat Loss Safely?

Creating a bigger deficit doesn’t always mean faster results. Your body has limits on how much fat it can burn per day.

Research shows the maximum safe fat loss is about 1% of body weight per week. For most people, that’s 0.5-1.5kg depending on starting weight.

Trying to lose faster by cutting calories too low leads to:

• Muscle loss instead of fat loss
• Slower metabolism
• Extreme hunger and cravings
• Higher chance of giving up

Slow and steady wins. The person who loses 1kg per week for 20 weeks ends up lighter and healthier than the person who crashes for 4 weeks, gives up, and regains everything.

Frequently Asked Questions

How accurate is the 7,700 calorie rule?
Very accurate for most people. Some research suggests it might be closer to 7,000-8,000 calories depending on individual metabolism, but 7,700 is the accepted standard used by dietitians and researchers worldwide.

Do I need to count calories forever?
No. Most people only need to track for 4-8 weeks to learn portion sizes and food values. After that, you can maintain weight by eating mindfully without tracking every meal.

What if I’m not losing weight despite the deficit?
First, make sure you’re tracking accurately. Most people underestimate food intake by 20-30%. If you’re truly in a deficit for 3-4 weeks with no change, see a doctor to check for thyroid issues or other medical conditions.

Should I eat back exercise calories?
No. The 1,100 calorie deficit already accounts for exercise. Eating back those calories means you’re no longer in the deficit needed to lose 1kg per week.

Is it normal for weight loss to slow down?
Yes. The first week you might lose 2-3kg (mostly water weight). After that, expect 0.5-1kg per week. Some weeks you won’t lose anything due to water retention, hormones, or increased muscle mass.

Can I drink alcohol and still lose weight?
Yes, but alcohol has 7 calories per gram (almost as much as fat). A standard beer has 150 calories, wine has 120. Factor these into your daily deficit if you choose to drink.

Do I need supplements to lose weight?
No. Save your money. No supplement burns fat effectively. Focus on whole foods, adequate protein, and consistent exercise. The only supplements worth considering are vitamin D and omega-3s for general health, not weight loss.

The Bottom Line

Creating a 1,100 calorie daily deficit through a combination of diet and exercise will help you lose 1kg per week safely and sustainably. Track your food, move your body, get enough protein, and be patient with the process.

Weight loss isn’t complicated, but it does require consistency. The methods that work are simple, proven, and don’t require expensive programs or special products. Start with small changes, build momentum, and trust the process.

If you’re struggling to create a deficit on your own, consider working with an accredited practising dietitian. In Australia, you can get Medicare rebates for dietitian visits with a GP referral, making professional support affordable for most people.