Weight loss timeline: your projected plateau

From your daily calorie intake, this simulator projects your weight trajectory using a published dynamic model (Hall et al., The Lancet, 2011): a projected plateau date, the real metabolic cost of holding it, and how it compares with the naive rule of 7,700 kcal per kg. For a calorie target on its own, our calorie calculator answers that more directly.

A published model, not a homemade formula

This simulator runs the reduced form of the dynamic body-weight-change model published by Kevin Hall and colleagues in 2011 in The Lancet — the same model behind the NIH’s Body Weight Planner. Unlike the popular 7,700-kcal-per-kg rule, which assumes a constant deficit produces constant weight loss month after month, this model tracks fat mass and lean mass separately and lets energy expenditure change as the body itself changes.

Why a plateau, not a straight line that keeps going

Two mechanisms slow weight loss over time, even at a constant intake. First, a lighter body mechanically burns less energy at rest and during activity, so the same food intake represents a shrinking deficit as weight drops. Second, the body itself turns down its own expenditure in response to sustained restriction — a measured, moderate effect called adaptive thermogenesis, which this simulator models with its own time constant rather than ignoring it or inflating it into a vague “slowed metabolism”.

Why the plateau date is always shown as a range

The activity level you select has a strong effect on the result, and it remains an estimate rather than a measurement. The “sedentary” tier used on this site (factor 1.2) is deliberately conservative, below the usual FAO/WHO reference band, and being one tier off between the level entered and the real one can shift the plateau by 3 to 6 kg. Rather than show a single figure at that illusory precision, the simulator reruns the same intake at the tier just above and just below the one chosen, and shows both edges.

What this simulator cannot tell you

The heaviest assumption is that intake is held exactly, every day, for years — something almost nobody does in practice. Most real-world plateaus arrive earlier than a model like this predicts, usually because intake drifts back up over time, not because metabolism has deteriorated. Expect a more visible drop in the first two weeks than the curve shows, too: that is water tied to glycogen stores, and it comes back. This model also does not account for medical conditions, medications that affect weight or appetite, or a measured body composition when none is entered.

When to talk to a health professional

Speak to a doctor or a registered dietitian before making any substantial change to how you eat, especially if you are pregnant or breastfeeding, under 18, over 65, taking medication, or living with a chronic condition. A professional can assess what this simulator cannot: medical history, real body composition, and how your own body responds over time. To place your starting weight in context, our page on BMI in adults is a useful companion reference.

Frequently asked questions

Why is the plateau shown as a range, never as one single number?

Because the result is highly sensitive to the activity level entered: the "sedentary" tier used on this site (1.2) is deliberately conservative, below the usual FAO/WHO reference band, and being one tier off from the real level can shift the plateau by 3 to 6 kg. So the simulator reruns the same intake against the tier just above and just below the one selected, and shows both edges — a single number would claim a precision this tool does not have.

Why does this simulator predict less weight loss than the "7,700 kcal per kg" rule?

Because energy expenditure is not fixed: it falls as weight drops (a lighter body burns less) and as the body adapts to reduced intake (adaptive thermogenesis). The 7,700-kcal rule assumes constant expenditure instead, so it systematically overstates loss the further out you project — often by more than 50% at one year, exactly the gap this simulator's comparison makes visible.

What is the figure shown under "the number a simple calculator won't give you"?

It is the gap between the real maintenance intake at the projected plateau, as this model calculates it, and what a standard calorie calculator would show for that same final weight. The gap exists because expenditure keeps falling as mass is lost and the body adapts — a static calculator cannot see that, and hands the difference back as an unexplained relapse.

Is this simulation personalised to me, or medically validated?

No, and the callout shown with every result says so directly: this is a statistical projection built from population averages, not an individual prediction or medical advice. Two people with identical numbers can end up on different real-world trajectories.

Do I need to enter my body fat percentage?

It isn't required: without it, the simulator estimates it from height, weight, age and sex using a published regression. Entering it when known — from bioelectrical impedance or another method — makes the simulation more accurate, since it bypasses that estimate.

Why might my real trajectory look different from what the chart shows?

The model assumes the entered intake is held exactly, every day, for years — something almost nobody actually does. Most people see their weight loss slow down earlier than a model like this predicts, usually because intake drifts back up over time, not because their metabolism has "broken". Expect faster loss in the first two weeks too: that is water, and it comes back.

This tool is informational and does not constitute a diagnosis or medical advice. Consult a healthcare professional.