Calorie deficit explained: how big should it be?

Why a percentage beats a fixed number

You will often see 500 kcal a day quoted as the standard deficit. It is a reasonable starting point for many people, but it treats a 55 kg woman and a 110 kg man the same, which does not make sense. A percentage of your own maintenance scales far better.

• Gentle (10 to 15% below maintenance): best for lean people, anyone training hard for performance, or those aiming for a slow body recomposition.
• Moderate (15 to 25%): the right choice for most people most of the time.
• Aggressive (25% or more): occasionally useful for short phases in people with a lot of fat to lose, ideally with coaching support. Not a long-term plan.

As a worked example, if your maintenance is about 2,400 kcal, a moderate deficit puts you around 1,800 to 2,050 kcal a day. If yours is 1,900 kcal, it is roughly 1,450 to 1,600. A kilo of body fat stores roughly 7,700 kcal, so a 500 kcal daily deficit works out at about half a kilo a week on paper, although real life is messier than the maths.

Setting your deficit in three steps

1. Estimate your maintenance. Use a formula for a first guess, then refine it by tracking your food and weight for two or three weeks. Our guide on how to work out your maintenance calories walks through both methods.
2. Take off 15 to 25% and round it to a number you can remember. Set a protein target of 1.6 to 2.2 g per kg of body weight a day at the same time, because protein is what stops the deficit eating into muscle.
3. Hold it for three to four weeks before judging it. Compare weekly average weights, not single mornings, and look for a loss of roughly 0.5 to 1% of body weight a week.

If the trend is slower than that and you are confident your tracking is honest, trim another 100 to 200 kcal or add a couple of thousand steps a day. If it is faster and you feel wrecked, add food back. Our guide on how fast you should lose weight explains why quicker is rarely better.

Food, movement or both?

You can create a deficit by eating less, moving more or a mix of the two. For most people a mix works best. Cutting 300 kcal from food and adding an extra 3,000 steps a day feels far easier than cutting 500 kcal from food alone.

Be careful about using training to earn food. Fitness trackers often overestimate what a session burns, and a hard class can make you hungrier than the calories it used. Treat exercise as the thing that keeps your muscle, fitness and health while dieting, and let food and daily steps do most of the work on the deficit. Steps and NEAT explains why walking is so underrated here.

Signs your deficit is too big

A deficit that is too aggressive rarely shows itself on day one. It creeps up over two or three weeks. Watch for these:

• Your lifts drop week after week rather than holding steady.
• You are constantly cold, irritable or struggling to concentrate at work.
• Sleep gets worse, or you wake up hungry in the night.
• You are losing more than about 1% of body weight a week after the first fortnight.
• Weekdays are rigid and weekends turn into a free-for-all.
• Periods become irregular or stop, which is a sign to raise intake and speak to your GP.

Any of these means pull the deficit back. Losing a little slower is almost always better than stopping altogether.

Mistakes that quietly shrink your deficit

Most people who say a deficit is not working are not lying. They are just missing things, and the same few leaks come up again and again.

• Untracked extras. A glug of oil in the pan, a milky coffee from the station, the kids' leftover fish fingers. Each is small; together they can add a few hundred kcal a day.
• Weekday deficit, weekend surplus. Two big days can cancel out five careful ones, which is covered in how to stop the weekend undoing your week.
• Moving less without noticing. Dieting often makes people sit more, which trims the deficit from the other side.
• Changing the plan every week. Water weight can hide fat loss for days at a time, so people panic and cut again before the first change has had a chance to show.

Fix the leaks before you cut food further. More often than not, that alone gets the trend moving again.

How long to stay in a deficit

There is no fixed limit, but most people do well with blocks of 8 to 16 weeks followed by a spell at maintenance. Long, unbroken diets tend to drag as hunger rises and daily movement falls. A planned diet break of a week or two at maintenance can make the next block easier to stick to.

Keeping your training consistent through a deficit matters as much as the food. Lycan Strength offers nutrition and accountability coaching alongside its classes if you want help setting numbers you can live with, and you can see how sessions fit your week on the class timetable.