A calorie deficit for complete beginners
Here is the whole idea. You spend a certain amount of energy each day staying alive and moving around. Eat less than that and your body covers the gap from stored fat. That is it — a calorie deficit is the only mechanism by which anyone has ever lost fat, and everything else is detail.
The hard part is not understanding it. It is that most people start by guessing their numbers and then cutting hard, which is two errors stacked. So here is a fortnight that does it in the other order.
Week one: change nothing
The first week of a calorie deficit should not contain a calorie deficit.
Eat exactly as you normally would and log all of it. You are not dieting this week, you are measuring. The point is to find your real baseline, because the number you will be subtracting from is your actual intake, not an equation’s guess at it.
This is where almost everyone gets a surprise, and it is usually one of four things:
- Cooking oil. A tablespoon is about 120 kcal. What people call “a drizzle” is routinely two or three.
- Drinks. A large latte is around 150 kcal, two pints about 400. Neither registers as eating.
- The untracked. Finishing a child’s plate, the biscuit by the kettle, tasting while cooking.
- Portion size. A “bowl” of cooked rice ranges from 150 g to 400 g. That is a 325 kcal spread on one item.
Three rules make the week worth having. Log before you eat, not at bedtime from memory. Log the bad days too — a week with an honest Saturday in it is the only week worth averaging. And do not change what you eat because you are writing it down. You will anyway, slightly, which is fine; just do not try to.
Any log works: paper, a notes app, or a tracker such as Caldown. What matters is that it is complete, not that it is clever.
Week two: subtract
Take your week-one daily average and cut 15–20% off it. That is your target.
Run the calculators as a sanity check and to get a deficit number with an expected rate attached — the arithmetic behind them is worth five minutes. If your logged average and the calculator’s estimate disagree sharply, the cause is almost always under-logging rather than an unusual metabolism.
Weigh your food, at least at first
People under-report what they eat by 20–30% on average, including people trying hard to be accurate. Eyeballing portions is the largest source of error in calorie counting, and a cheap kitchen scale removes it.
Weigh everything for two or three weeks, then estimate the meals you eat constantly and weigh the new ones. Rice, pasta and oats get weighed dry; oil and nut butters get weighed forever, because a wrong guess there costs 200 kcal.
What the scale will do
Weigh yourself daily, under the same conditions — morning, after the loo, before food — and then ignore the daily number. You are collecting it to average it.
| When | What the scale does | What it means |
|---|---|---|
| Days 1–5 | Drops 1–2 kg (2–4 lb) fast | Mostly glycogen and the water bound to it. Not fat |
| Weeks 1–2 | Settles into a slow decline | This part is fat |
| Around week 3 | Flat, or up | Real loss hidden under water: salt, stress, poor sleep, a hard session |
| Week 4 on | Decline resumes, often as a sudden step | The average was moving all along |
Compare one week’s average with the previous week’s, never one day with another. A 0.5 kg (1 lb) swing between mornings is normal and carries no information. The week-three stall is the single most common point at which people quit, and in most cases nothing had gone wrong at all.
The four things not to do
Do not cut to 1,200. It is not a target, it is a number people found online. Deep deficits make protein nearly impossible to hit, make hunger the main event of the day, and buy very little: how big the deficit should be has the reasoning.
Do not ban foods. Every banned food is a future binge with a date on it. Build the budget so the thing you actually like still fits in it.
Do not add five gym sessions at once. Exercise is a smaller share of daily energy expenditure than most people assume, and week two should test one change so you know what moved it. Add training in week three, for muscle and health rather than as a calorie tool.
Do not change your diet style at the same time. Going keto, vegan or intermittent on day one adds a second experiment to the one you are running. No eating philosophy does the work; keep your food the same and change the amount.
What a fortnight buys you
Not much weight — maybe 1–2 kg (2–4 lb), much of it water. What you get instead is a real baseline, a calibrated eye for portions, and a scale you can read without panicking. Add enough protein and the next three months mostly run themselves.
General information, not medical advice.