Written by Rachel Orriss | Last updated July 2026 | 4 min read
How Much Weight Can I Lose in a Month? The Realistic Answer
Most people want to know what is actually achievable in a month — not the best-case scenario from a crash diet, but a realistic figure for sustainable fat loss. This guide gives you the honest answer and explains what drives the result.
Quick answer: A realistic and sustainable rate of fat loss is 0.5–1kg per week — which means 2–4kg over a month. Faster losses are possible but usually involve water weight and muscle loss, which rebounds quickly. The goal is a method you can maintain for three months, not one that produces dramatic results in two weeks.
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What determines how much you lose in a month
Calorie deficit size
To lose 1kg of fat you need to burn approximately 7,700 calories more than you consume. A daily deficit of 500 calories produces roughly 0.5kg of fat loss per week — 2kg per month. A 750-calorie daily deficit produces approximately 3kg per month.
Starting weight
People with more weight to lose typically lose faster in the first month, partly because the same calorie deficit represents a larger percentage reduction, and partly because initial losses include water weight as glycogen stores deplete.
Consistency
A 500-calorie daily deficit maintained for 30 days produces 2kg of fat loss. The same deficit maintained for 20 days and abandoned for 10 produces significantly less. Consistency over the full month matters more than the size of the deficit.
Protein intake
Higher protein intake during a calorie deficit preserves muscle mass. This matters because muscle burns more calories at rest. Losing muscle alongside fat reduces your metabolic rate and makes it harder to maintain results.
Why crash diets produce fast but temporary results
Very low calorie diets (under 800 calories per day) produce rapid initial weight loss — often 4–6kg in the first two weeks. But most of this is water weight and glycogen, not fat. When normal eating resumes, this weight returns within days.
The sustainable approach is a moderate deficit (400–600 calories per day) maintained consistently. This produces 2–3kg of genuine fat loss per month — slower, but it stays off.
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Frequently asked questions
How much weight can I realistically lose in a month?
A sustainable rate of fat loss is 0.5–1kg per week — 2–4kg over a month. Faster losses are possible but usually involve water weight and muscle, which rebounds quickly when normal eating resumes.
Is losing 5kg in a month realistic?
5kg of genuine fat loss in a month would require a daily deficit of approximately 1,300 calories, which is very difficult to sustain and risks muscle loss. It is possible on a crash diet but most of the loss will be water weight that returns quickly.
How does a meal replacement help with weight loss?
A meal replacement like Formula 1 removes decision-making from one meal per day and provides a controlled number of calories (approximately 200–220 with semi-skimmed milk) and high protein (18–20g). This makes it easier to maintain a consistent daily deficit without tracking every meal.
