Losing 1 kg per week requires a total caloric deficit of roughly 7,700 calories over seven days, which works out to about 1,100 calories per day. That’s a significant deficit, and while it’s achievable for many people, it sits at the upper edge of what health guidelines consider sustainable. The CDC notes that a steady loss of 1 to 2 pounds (roughly 0.5 to 0.9 kg) per week is the range most likely to stay off long-term. So 1 kg per week is ambitious but possible, especially if you have more weight to lose.
The Calorie Math Behind 1 kg of Fat
One kilogram of body fat stores approximately 7,700 calories. Body fat isn’t pure fat; it’s mixed with water and protein, so it contains slightly less energy than pure fat would. To lose that kilogram in seven days, you need to burn 7,700 more calories than you consume across the week. Divided evenly, that’s about 1,100 calories per day.
For context, a 500-calorie daily deficit produces roughly half a kilogram (about one pound) of loss per week. Doubling that rate means you need to find the other 600 or so calories through some combination of eating less and moving more. Trying to get all 1,100 calories from diet restriction alone can leave you underfueled, so splitting the work between food and activity is more realistic and more sustainable.
Where the Deficit Should Come From
A practical split for most people: cut 500 to 700 calories from your daily food intake and burn the remaining 400 to 600 through physical activity. The exact numbers depend on your starting weight, current activity level, and how much you’re eating now. Someone consuming 2,800 calories a day has more room to cut than someone already eating 1,800.
Reducing portion sizes, swapping calorie-dense snacks for higher-volume foods like vegetables and lean protein, and cutting liquid calories (alcohol, sugary drinks, specialty coffee) are the simplest levers. These changes alone can account for several hundred calories without requiring you to overhaul every meal.
On the activity side, don’t underestimate everyday movement. Research on non-exercise activity thermogenesis (the calories you burn through walking, standing, fidgeting, and housework) shows it’s the most variable component of your daily energy expenditure. For most people, formal exercise accounts for a surprisingly small slice of total calorie burn, sometimes near zero. Researchers have found that increasing daily low-level movement can add 280 to 350 calories of expenditure per day, which is a meaningful chunk of your deficit goal. Walking more, taking stairs, standing while working, and doing active errands all contribute.
Why Protein Matters More During a Deficit
When you eat significantly fewer calories than you burn, your body doesn’t exclusively pull energy from fat. It also breaks down muscle tissue. The larger the deficit, the greater this risk. Since losing muscle slows your metabolism and undermines the results you’re working toward, protecting it is essential.
The most effective strategy is combining higher protein intake with resistance training. Research published in Current Opinion in Clinical Nutrition and Metabolic Care found that consuming 1.2 to 1.6 grams of protein per kilogram of body weight daily, spread across meals, optimally stimulates muscle repair and suppresses muscle breakdown during a deficit. For a 75 kg person, that’s roughly 90 to 120 grams of protein per day. In one study, young men eating 2.4 g/kg while maintaining a 40% energy deficit actually gained lean mass while losing fat, though that level of protein isn’t necessary for most people.
At minimum, aim for 1.2 g/kg per day. Pair that with strength training two to three times per week. Resistance exercise is the single most powerful tool for preserving muscle when calories are restricted, and protein amplifies that effect.
What Happens in the First Week
You’ll likely see more than 1 kg drop in your first week, and that’s normal. Much of the early loss is water, not fat. Your body stores carbohydrates as glycogen in your muscles and liver, and each gram of glycogen holds roughly 3 grams of water with it. As you reduce calories (and especially carbohydrates), you burn through those glycogen stores and release the associated water. This can produce a dramatic initial drop on the scale that has nothing to do with fat loss.
After the first week or two, the rate of loss typically slows as glycogen depletion stabilizes. This is when true fat loss becomes the primary driver, and progress on the scale more accurately reflects what’s happening in your body. Don’t let the slower pace discourage you. It’s the shift from water loss to fat loss, and it means the plan is working.
Why Weight Loss Slows Down
Nearly everyone hits a plateau, usually within the first few months. This isn’t a failure of willpower. It’s your body’s biology actively working against further loss. Several overlapping mechanisms drive it.
First, your resting metabolic rate drops more than your smaller body size alone would predict. This phenomenon, called metabolic adaptation, means your body becomes more efficient at conserving energy. Data from long-term calorie restriction studies show this adaptation can reduce your resting metabolism by 5 to 8% beyond what the loss of body mass accounts for. In one two-year study, metabolic adaptation was 8% at three months, gradually settling to about 5% by 24 months, and it persisted even after weight stabilized. Your body essentially recalibrates to a lower energy setpoint.
Second, hormonal shifts increase hunger. Calorie restriction lowers leptin (which signals fullness) and raises ghrelin (which signals hunger). You genuinely feel hungrier, and your body reduces the energy you burn through everyday movement. You fidget less, walk slower, and generally become less physically active without realizing it. All of this narrows your caloric deficit over time.
The practical response: recalculate your calorie targets every few weeks as your weight drops, and periodically increase activity to compensate for the metabolic slowdown. Some people also benefit from brief “diet breaks” where they eat at maintenance for a week before resuming the deficit.
Risks of Losing Weight Too Fast
Pushing significantly beyond 1 kg per week, particularly through very low-calorie diets, raises your risk of gallstones. The National Institute of Diabetes and Digestive and Kidney Diseases explains why: when you don’t eat for long periods or lose weight rapidly, your liver releases extra cholesterol into bile, and your gallbladder doesn’t empty properly. That combination creates the conditions for gallstone formation. The risk is highest with crash diets and very low-calorie plans.
For people who are overweight or have obesity, experts recommend starting with a goal of losing 5 to 10% of starting body weight over six months. For someone weighing 90 kg, that’s 4.5 to 9 kg over 24 weeks, roughly 0.5 to 1 kg per week, which aligns well with the 1 kg target. The key is avoiding extreme restriction. Keeping your daily intake above 1,200 calories (for most women) or 1,500 calories (for most men) helps prevent nutritional deficiencies and excessive muscle loss.
A Realistic Weekly Plan
Here’s what a week targeting 1 kg of loss looks like in practice:
- Daily calorie reduction: 500 to 700 calories below your maintenance level, achieved through smaller portions, fewer snacks, and fewer liquid calories.
- Daily movement: 8,000 to 12,000 steps or equivalent activity, contributing 200 to 350 extra calories of expenditure through everyday movement.
- Structured exercise: 3 to 4 sessions per week combining resistance training with moderate cardio (brisk walking, cycling, swimming), burning an additional 200 to 400 calories per session.
- Protein intake: 1.2 to 1.6 g per kilogram of body weight daily, spread across three or four meals.
Weigh yourself at the same time each day and track the weekly average rather than fixating on any single reading. Daily weight can fluctuate by 1 to 2 kg based on hydration, sodium intake, and digestive contents. The weekly trend is what matters. If your average is dropping by roughly 0.7 to 1 kg per week, you’re on track. Some weeks will show more, some less. Consistency over months produces the results that daily obsession never will.