Calories: How Deficit and Surplus Work. A Complete Guide for Beginners

Let’s figure out how this really works, without myths, complex formulas, and with clear examples.

What is a calorie? (In simple terms)

Imagine your body is a car. Calories are the fuel. Without “fuel,” you wouldn’t take a single breath, step, or heartbeat. You get calories only from food and drinks.

But there’s a nuance: if you pour more fuel into the tank than needed for the trip, the excess doesn’t disappear. The car can’t throw it away — it has to store it in the trunk. The body does the same, except the “trunk” is fat cells.

Key idea: Calories are not the enemy — they are energy for life. Problems begin only when there are consistently too many or too few.

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How does the body spend calories?

Most beginners mistakenly think calories are burned only during workouts. In reality, that’s just the tip of the iceberg. Your daily expenditure consists of three parts:

Basal metabolism (60–75% of total expenditure).
Energy for breathing, heartbeat, brain function, maintaining body temperature. Even if you lie down all day, your body burns a significant number of calories.

Thermic effect of food (about 10%).
Yes, digestion also requires energy. Protein requires the most, fats the least.

Physical activity (15–30%).
This includes morning exercises, walking to the store, even typing on a keyboard — and of course, structured workouts.

Example:
For a 30-year-old woman, 165 cm tall and weighing 65 kg, working in an office:

Basal metabolism ≈ 1300–1400 calories
Activity + digestion ≈ 600–700 calories
Total daily need ≈ 2000 calories

If she eats exactly 2000 calories — her weight stays the same. This is called caloric balance (maintenance).

What is a calorie deficit? (How to lose weight)

A deficit is when you eat less than your body spends. That means you provide less “fuel” than needed for all activities. Where does the body get the missing energy? From its own reserves — first glycogen in the liver and muscles, then fat.

How to create a safe deficit (example with scheme)

Let’s take our office worker (2000 calories expenditure):

Too small deficit (1900 calories).
Weight loss will be very slow. You may not notice results for months and lose motivation.
Optimal deficit (1500–1700 calories).
Subtract 15–20% from maintenance. You’ll lose 0.5–1 kg per week, mostly from fat. Hunger will be moderate.
Huge deficit (1000 calories or less).
Starvation dieting. Weight drops quickly at first, but you lose muscle along with fat, metabolism slows down (“economy mode”), and after returning to normal eating, weight comes back with extra.

How to make a deficit comfortable? (Tricks)

Add activity, don’t just cut food.
Eat 200 fewer calories (skip candy) AND walk 3 km (burn ~150 calories) — total deficit = 350. Easier than starving.

Eat more high-volume foods.
200 calories can be a small piece of cake or a huge bowl of salad (cucumbers, tomatoes, greens). Your stomach will feel full, but calories remain low.

What is a calorie surplus? (How to gain weight)

A surplus is when you eat more than your body spends. It’s necessary for muscle growth (if you train) or for gaining weight when underweight.

But важно: surplus does not mean “eat everything.”

Where extra calories go depends on your actions:

Surplus + strength training = MUSCLE growth (plus a bit of fat, which is normal)
Surplus + couch = FAT gain

Example:
A 25-year-old man, 70 kg, goes to the gym 3 times per week. His maintenance is 2600 calories.

For muscle growth, he needs a small surplus: +200–300 calories → 2800–2900 per day.

If he eats 3500 calories (huge surplus), he’ll just gain fat — because the body cannot build muscle faster than genetics allow.

The most common beginner mistakes

1. “I’ll burn more than I eat — eat a 500 kcal cake, then do 2 hours on a bike.”
Pointless. Machines often overestimate calories burned. Also, it’s physically hard to compensate for overeating. Easier not to overeat. Remember: controlling intake is easier than expenditure.

2. “I don’t eat after 18:00 — so I’m in a deficit.”
No. What matters is total daily intake. If you eat 3000 calories before 18:00 — you’re still in a surplus. наоборот: a light dinner at 21:00 within your norm is fine.

3. “If calories are low — can I eat only sweets?”
You can, but you’ll feel extremely hungry, irritable, and weak. 1500 calories from sweets cause blood sugar spikes and crashes → strong hunger.
1500 calories from grains, meat, vegetables, and fats keep you full for 5–6 hours. Quality of calories matters.

How to calculate YOUR maintenance? (Step-by-step)

This is the most valuable part. Don’t rely on internet numbers. Do this:

Weigh yourself and track your food for 7–10 days. Eat normally. Record EVERYTHING: tea with sugar, cookies, oil in salad.
Calculate average daily calories (use apps like MyFitnessPal or FatSecret).
Observe weight changes:

Weight unchanged → maintenance = your average calories
Weight increased → surplus → subtract 200–300 calories
Weight decreased → deficit → add 200–300 calories

Example:
7-day average = 2100 calories. Weight stable → maintenance = 2100 kcal.

Weight loss: 2100 - 300 = 1800 kcal/day
Muscle gain: 2100 + 200 = 2300 kcal/day + strength training

Quick summary (to remember)

Maintenance calories → weight stays the same
Deficit (below maintenance) → weight loss (fat)
Safe deficit = -15–20%
Surplus (above maintenance) → weight gain (muscle + fat)
For muscle: +10–15% + training

Your main tool is not even training — it’s the ability to consciously manage your nutrition: sometimes add, sometimes subtract calories.

Don’t rush. Radical changes are extreme stress for the body. Small but consistent changes (200–300 calories) work better.

Start simple: for one week, just record everything you eat. No judgment. Just collect data. This is the first step to ensuring your “fuel tank” always has exactly the amount of “fuel” you personally need.

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