Calorie Calculator

How large a deficit should be, and what happens when it is too big

A deficit means eating below what you spend. Everything else — meal timing, food choice, which app you use — sits downstream of that. The question that actually matters is how large the gap should be, and the intuitive answer is usually too large.

Why bigger is not better

A larger deficit does produce faster loss, for a while. The costs arrive later and are easy to miss at the start.

• Lean mass. Aggressive deficits draw more heavily on muscle. Losing muscle lowers resting expenditure, which makes both further loss and eventual maintenance harder.
• Micronutrients. Below roughly 1,200 calories a day it becomes genuinely difficult to meet vitamin and mineral needs from food alone.
• Adherence. The most common failure of a large deficit is that it stops. Restriction that feels heroic in week one is rarely intact in week six.
• Function. Sleep, mood, training quality and concentration all degrade under sustained heavy restriction, and each makes the plan harder to keep.

Practical floors

Public health material commonly treats roughly 1,200 calories a day for women and 1,500 for men as a lower bound for unsupervised dieting. These are rules of thumb rather than clinical thresholds, and they exist mainly because below them nutritional adequacy becomes hard to achieve from food.

Very-low-calorie programmes below these figures do exist and can be appropriate — but they are medically supervised, with bloodwork and supplementation. That supervision is the difference. It is not something to reproduce alone from a website.

What makes a deficit hold

• Enough protein. It preserves lean mass and is the most satiating macronutrient per calorie. See protein, carbohydrate and fat.
• Resistance training. The clearest signal available to the body that muscle is worth keeping.
• Volume and fibre. Vegetables, legumes and whole grains fill a plate for comparatively few calories.
• Sleep. Short sleep makes appetite regulation measurably harder, and this is under-rated relative to how much it affects adherence.
• A trend, not a reading. Daily fluctuation of a kilogram from hydration, sodium and digestion is normal. Judge across three or four weeks.

Plateaus

Loss slowing after a few months is expected, not a malfunction. A lighter body spends less, so the original deficit has shrunk in real terms. The responses, in rough order of preference: recalculate TDEE at your current weight, then look honestly at portion drift and untracked intake, then consider adding activity before cutting further. Repeatedly cutting calories to chase the same rate is how people arrive at intakes they cannot sustain.