Calorie Deficit UK Guide: How Many Calories Should I Eat to Lose Weight?

A calorie deficit is the one thing every successful fat loss plan has in common. This calorie deficit UK guide explains how to work out your maintenance calories, how big your deficit should be, and how to make it sustainable, the same way we set it up with clients in Archway.

What is a calorie deficit?

A calorie deficit simply means eating fewer calories than your body uses. When that happens, your body makes up the difference from its stored energy, mostly body fat. Do it consistently and your weight comes down over time.

It doesn't matter whether you get there through keto, intermittent fasting, a meal plan or just eating a bit less. If you lose fat, you were in a deficit. The best approach is simply the one you can keep doing.

Step 1: find your maintenance calories (TDEE)

Your maintenance calories, sometimes called TDEE (total daily energy expenditure), is roughly how much you burn in a day. It is made up of:

• Your resting metabolism, the energy needed to keep you alive. This is the biggest part.
• Daily movement, everything from walking to the tube to fidgeting at your desk. This varies hugely between people.
• Exercise, your planned workouts.
• Digesting food, a small amount, slightly higher for protein.

Any calculator gives you an estimate, not an exact number. Use our free calorie calculator for a starting point, then treat it as a hypothesis you test over the next two to three weeks.

How many calories should I eat to lose weight?

For most people a moderate deficit works best. The NHS commonly suggests eating around 600 fewer calories a day than you need to maintain your weight. For many adults that leads to a steady loss of about 0.5-1kg a week, which is the rate we aim for with clients.

A simple way to set it:

1. Get your estimated maintenance calories from the calculator.
2. Subtract around 500-600 calories.
3. If that number looks very low for you, use a smaller deficit instead. We never suggest going below roughly 1,200 calories a day without medical supervision.

Smaller, lighter people may need a smaller deficit. Taller, heavier or very active people can often lose weight eating more than they expect.

Why crash diets backfire

Very low calorie diets look faster on paper, but they usually cost you in other ways:

• You lose more muscle, which leaves you weaker and less toned.
• Hunger, low energy and poor sleep make it hard to stick to.
• Training quality drops, so you burn less and recover worse.
• Most people rebound once the diet ends.

The safest way to lose weight, as the NHS puts it, is gradually, with changes to food and activity you can keep for life. A steady deficit you hold for 12 weeks beats a severe one you quit after 10 days.

How to stay full in a calorie deficit

Being in a deficit doesn't have to mean being hungry all the time. These help the most:

• Protein at every meal. It keeps you fuller and helps protect muscle while you lose fat. Our guide to protein intake explains how much to aim for.
• Fibre and volume. Vegetables, fruit, beans, oats and potatoes fill you up for relatively few calories.
• Fewer liquid calories. Fizzy drinks, alcohol, large coffees and juices add up quickly without filling you.
• Regular meals. A rough routine stops you arriving at dinner starving.
• Strength training. It gives your body a reason to keep muscle while the fat comes off.

Tracking and adjusting your calorie deficit

Pick a tracking method that suits you

You don't have to weigh every gram forever. Options from most to least precise:

• Full tracking in an app for a few weeks. This teaches you what portions actually look like.
• Protein and calories only, ignoring the other numbers.
• Portion guides using your hand: a palm of protein, a fist of vegetables, a cupped hand of carbs, a thumb of fats.
• A set meal plan where the numbers are done for you. This is what our nutrition coaching provides.

When and how to adjust

Weigh yourself a few times a week at the same time of day and look at the weekly average, not single days. Water, salt, hormones and digestion all make daily weight jump around.

If your weekly average hasn't moved for two to three weeks and you've genuinely been consistent, reduce your intake by around 100-200 calories a day or add more daily steps. If you're losing much faster than 1kg a week and feel drained, eat a little more. If progress stalls and you can't see why, read why am I not losing weight.

Please note: if you have a medical condition, take medication, are pregnant or breastfeeding, or have a history of disordered eating, speak to your GP before starting a calorie deficit. Never go below around 1,200 calories a day without medical supervision.

Getting it right with a coach

Most people know they need to eat less. The hard part is setting the right number, sticking to it through busy weeks and knowing when to change it. That's what our weight loss coaching does: a food plan with calorie and protein targets, 1-to-1 strength training in our Archway studio, InBody scans and weekly check-ins. Across our 12-week programme, the average client loses 6-16kg, though results vary with your starting point and consistency.

Want this coached 1-to-1? We set your calorie and protein targets for you, then adjust them every week. Book a free consultation at our Archway studio.

Frequently asked questions

How many calories should I eat to lose weight UK?

Start with your estimated maintenance calories and eat around 500-600 fewer a day. The NHS commonly suggests about 600 fewer calories than you need to maintain your weight, which for many people gives 0.5-1kg of loss a week.

Is a 1,200 calorie diet safe?

Around 1,200 calories a day is the lowest we would suggest for adults without medical supervision, and most people can lose weight eating more than that. Speak to your GP if you're considering going lower.

What is the safest way to lose weight according to the NHS?

The NHS recommends losing weight gradually, at around 0.5-1kg a week, through a combination of eating fewer calories and being more active, with changes you can maintain long term.

Why am I not losing weight in a calorie deficit?

Usually because intake is higher than you think, especially at weekends, or because water retention is hiding fat loss. Track carefully for two weeks and compare weekly averages. Our plateau guide covers the common reasons.

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