Calorie Deficit Explained Simply

In short

A calorie deficit just means eating less than your body burns in a day.
A 15–20% deficit below maintenance is the sweet spot for most people.
Bigger deficits lose weight faster short-term, but are harder to sustain and often cost muscle.

What a calorie deficit actually is

Your body burns a certain number of calories a day just existing, moving, and digesting. That number is your maintenance. A deficit means eating below that number, so your body pulls the difference from stored fat.

Person weighing food on a kitchen scale to track calorie intake

How big should the deficit be?

Deficit size	Weekly loss (approx.)	Sustainability
10%	~0.5 lb/week	Very easy, slow results
15–20%	~1 lb/week	Sustainable, recommended for most
25%+	1.5+ lb/week	Hard to sustain, higher muscle-loss risk

Why crash deficits usually backfire

Extreme hunger makes adherence collapse within a few weeks for most people
Very low intake makes it hard to hit your protein target, so you lose muscle along with fat
Aggressive deficits tank energy for training, so workouts get worse right when you need them most

When to adjust your numbers

Recalculate when...

You have lost 10–15 lbs since your last calculation
Weight loss has stalled for 3+ weeks with consistent tracking
Your activity level changed significantly (new job, new training split)

Questions, answered.

How big should my calorie deficit be?

A deficit of 15–20% below your maintenance calories is enough for most people to lose fat steadily without extreme hunger or muscle loss.

Why did I stop losing weight even though I am still in a deficit?

As you lose weight, your maintenance calories drop too. A deficit that worked at a higher bodyweight can become maintenance at a lower one. Recalculate every 10–15 lbs lost.

Is it bad to eat below 1200 calories?

For most adults, very low intakes are hard to sustain, make it difficult to hit protein targets, and often lead to muscle loss. A moderate deficit almost always wins long term.

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