How many calories do you need to cut to lose a stone?

"How many calories do I need to cut to lose a stone?" is a question I hear every autumn, usually from someone with a wedding, a holiday or January in mind. There's a simple answer and an honest one, and you need both.

The rough maths

A stone is 14lb, or 6.35kg. A rule of thumb you'll see quoted a lot is that a kilo of body fat holds roughly 7,700 calories. On that sum, a stone works out at close to 49,000 calories, which you'd cover in about 12 weeks with a gap of 600 calories a day.

It's a handy starting point, but it's only an estimate. Your weight loss isn't all fat, and your body doesn't stand still while you eat less. A smaller body uses less energy, and some people move a little less without noticing when food is tighter.

That's why progress usually slows. A Lancet modelling study by Kevin Hall and colleagues found that body weight responds slowly to a change in calories, and that a fixed calorie cut doesn't keep producing the same weekly loss for ever. So if your first few weeks go well and then things ease off, that's normal, not failure.

What the NHS suggests

The NHS keeps it simple. Its calories and weight loss page says to aim to reduce your intake by around 600 calories a day, and calls this "a safe and sustainable way to lose weight".

The NHS 12-week weight loss plan aims for a rate of 0.5kg to 1kg (1lb to 2lb) a week. For most men, it says that means no more than 1,900 calories a day, and for most women no more than 1,400. It also points out that you can get a more personal target, and that the plan is for healthy adults with a BMI of 25 or over, not for children or pregnant women.

Put those together and a stone at a safe pace usually takes somewhere between about 6 and 13 weeks. That's why I steer people away from "lose a stone in two weeks" plans. Anything that fast means eating very little, often losing water and some muscle rather than just fat, and it is hard to keep up.

Finding your own number

The NHS figures are averages. A tall, active man and a shorter woman who sits at a desk all day need very different amounts. Here's how I'd set yours.

1. Estimate your starting point. Our free calorie deficit calculator gives you a rough maintenance figure and a target. Treat it as a first guess.
2. Track honestly for a week. Weigh and log what you actually eat, including oils, drinks, sauces and the bits you pick at. The NHS page suggests looking at a typical day first, then finding where the 600 calories can come from.
3. Weigh yourself regularly and look at the trend. Daily weight jumps around with water, salt and hormones. Compare weekly averages, not single mornings.
4. Adjust after 3 or 4 weeks. If the trend is roughly 0.5kg to 1kg a week, carry on. If nothing has moved, check your logging before you cut further. If you're losing faster than that and feel drained, eat a bit more.

The NHS splits the 600 calories across the day: about 100 from breakfast, 200 from lunch, 200 from dinner and 100 from snacks. Small swaps add up faster than one dramatic change.

Logging is easier when something does the adding up for you. The FitFitCity food diary counts the calories, and you can try it free for a week with no card needed.

Keep the muscle while you lose the fat

How you lose the stone matters as much as how fast. Two things help most.

Protein. Getting enough protein at each meal helps you feel full and supports muscle while you're eating less. Our guide on how much protein you need explains how to work out a sensible amount, and our cheap high-protein meals make it easier on a UK food budget.

Strength training. Two or three sessions a week give your body a reason to hold on to muscle. You'll look and feel better at the end, and you'll find it easier to keep the weight off. If you're new to it, our beginner's 3-day gym plan is a good place to start. Its main lifts, including the goblet squat, dumbbell bench press and leg press, each have a step-by-step page in our exercise library.

If you'd like more on the health side, our post on losing 5% of your body weight in midlife looks at what a UK study found about modest weight loss.

Who should check with a GP first

The NHS says to talk to a GP or healthcare professional before changing your diet if you have a medical condition, follow a special diet for your health, or have had an eating disorder. Don't try very low calorie diets without medical supervision, and if you take medicines for diabetes or blood pressure, speak to your care team before cutting calories.

If you'd like a food diary, calorie target and training plan in one place to keep you on track week by week, that's what a FitFitCity membership is for.