Bo guide
Short answer
For most adults, 1,200 calories is too low. For a 75 kg woman with a TDEE of 1,900–2,100, it creates a 700–900 calorie daily deficit — well beyond the 300–500 range that evidence supports for sustainable fat loss with muscle retention.
General information, not medical advice. Written from published sources, which are listed at the end. It is not a substitute for a doctor, pharmacist or registered dietitian who knows your situation.
In this guide7 sections · 3 min
1,200 is the most quoted number in dieting and one of the least justified. It is not a floor derived from physiology — it is a round number that stuck.
Why it is usually too aggressive
Take a 75 kg woman with a total daily energy expenditure of 1,900–2,100 calories. Eating 1,200 puts her in a 700 to 900 calorie daily deficit. The evidence-supported range for fat loss while retaining muscle is 300 to 500.
A deficit that size is not twice as effective. It is harder to hold, costs more lean mass, and the fast early drop is substantially water.
| Deficit per day | Roughly | Realistic outcome |
|---|---|---|
| 300–500 cal | 0.5–1 lb / week | Sustainable, muscle largely retained |
| 700–900 cal | 1.5–2 lb / week | Hard to sustain, more lean loss, high rebound risk |
The part that compounds: losing muscle
This is the reason an aggressive deficit is worse than a moderate one even if you could hold it. Weight lost in a steep deficit contains a larger share of lean tissue, and muscle is metabolically active — so losing it lowers your maintenance.
You then finish the diet lighter but with a lower maintenance than someone who lost the same weight slowly, which means a smaller calorie allowance to hold your new weight, which makes regain easier. The aggressive route does not just cost more on the way down; it leaves you in a worse position at the bottom.
When 1,200 is actually reasonable
It is not universally wrong. A small, sedentary woman — say 150 cm and 45 kg with a desk job — might have a TDEE around 1,400–1,500. For her, 1,200 is a moderate 200–300 calorie deficit and perfectly sensible.
The problem is that the number gets applied to everyone regardless of size and activity, which is how a moderate deficit for one person becomes a severe one for another.
The nutrition problem
Separately from the deficit size: at 1,200 calories it becomes genuinely difficult to hit protein, fibre, and micronutrient requirements. The lower the intake, the less room for error, and nutrient shortfall is a real risk rather than a theoretical one.
Concretely, a 70 kg person targeting 1.8 g/kg of protein needs about 126 g — roughly 500 calories, or 42% of a 1,200 calorie budget, before a single vegetable. Fitting adequate fibre, essential fats, iron and calcium into the remaining 700 calories is possible but leaves no margin at all.
Why adherence is the real variable
Trials comparing diets tend to find that the specific approach matters far less than whether people stick to it. That reframes the whole question: a 400 calorie deficit held for six months beats an 800 calorie deficit abandoned in week five, even though the second one looks better on paper.
Very low intakes also drive the cycle directly. Severe restriction raises hunger, lowers everyday movement, and makes an eventual break more likely — and the break is rarely proportionate.
A better approach
- Estimate your maintenance, or simply log what you currently eat for a week without changing anything.
- Subtract 300–500. That is your target.
- Prioritise protein within it — it protects muscle and does the most for hunger.
- Track weight as a weekly average and adjust after three weeks, not three days.
- Add resistance training if you can. It is the other half of steering weight loss away from muscle.
When to stop and get help
Some signals mean the answer is not a different number. Persistent preoccupation with food, guilt or panic around eating, hiding what you eat, exercising to "earn" meals, loss of periods, hair thinning, or feeling cold and exhausted all the time are reasons to speak to a doctor rather than adjust a target.
