Diet Simulator
Enter your daily step count and what you usually eat to see what you will weigh in a few months. It models the drop in metabolism and metabolic adaptation, so plateaus show up too.
What this page helps you check
Enter your height, weight, and daily step count, then pick how you usually eat. The chart shows what you would weigh month by month, so you can check whether a weekly treat really costs you the diet.
- Set a realistic timeline before starting a diet
- See whether you are eating above or below your maintenance calories
- Check whether you can lose weight without giving up your favourite food
- Compare walking more against eating less
- See when a plateau is likely to arrive and what happens after it
How to read the result
As you lose weight your resting metabolism, your daily activity, and even the same number of steps all burn less, so the same diet takes off less each month. The curve flattening is not a modelling glitch, it is the plateau that happens in real life. If you are losing slower than predicted, doubt the calorie estimate first: self-reported intake is underestimated by 20-30% in study after study.
When you have no idea what you eat
Pick the closest match in the breakfast, lunch, dinner, and snack menus and an estimate fills in automatically. You do not need to have been logging anything.
There is a more reliable shortcut. If your weight has been stable lately, your actual intake must be close to your maintenance calories, so the maintenance button pins down your real eating level without any logging. Work down from there.
Do not count your walk twice
Walks and commutes your phone already tracked are covered by the step count. Adding the same walk under workouts can nearly double the calories you think you burn.
Use the workouts section only for what steps miss: weight training, swimming, cycling, or a treadmill session your tracker does not pick up.
Why this differs from the 3,500 kcal rule
Most diet calculators divide your deficit by 3,500 kcal per pound of fat. Over a few weeks that is close enough, but projected months ahead it always overestimates the loss.
In reality, every kilogram lost lowers your resting metabolism, your daily activity, and the energy cost of walking the same distance, and metabolic adaptation lowers expenditure further. The daily deficit shrinks even though the diet has not changed. This calculator follows Hall's dynamic weight model and recalculates that every single day.
How treats are counted
A burger meal may be 900 kcal, but it replaces a normal 600 kcal dinner, so the real addition is about 300 kcal. Counting only the surplus keeps the projection honest instead of punishing every meal out twice.
Snacks and sugary drinks are different: they sit on top of your meals rather than replacing one, so the whole amount counts. That is why 300 kcal of chips costs you more than 300 kcal inside a meal.
What your steps burn (132 lb / 60 kg, 5 ft 3 in / 160 cm)
Stride is estimated from height, and resting metabolism is subtracted.
| Steps per day | Distance | Calories burned |
|---|---|---|
| 3,000 | ~1.4 mi | ~68 kcal |
| 5,000 | ~2.2 mi | ~113 kcal |
| 8,000 | ~3.6 mi | ~181 kcal |
| 10,000 | ~4.5 mi | ~227 kcal |
| 15,000 | ~6.7 mi | ~340 kcal |
Derived from walking at 3.0 METs (Ainsworth BE et al., 2011)
Calories burned per session (132 lb / 60 kg, 30 minutes)
Net of resting metabolism. The heavier you are, the more the same workout burns.
| Activity | METs | 30 minutes |
|---|---|---|
| Walking (2.5 mph) | 3.0 | ~63 kcal |
| Brisk walking (4 mph) | 5.0 | ~126 kcal |
| Strength training (machines) | 5.0 | ~126 kcal |
| Cycling (10-12 mph) | 6.8 | ~183 kcal |
| Jogging (5 mph) | 8.3 | ~230 kcal |
| Running (6 mph) | 9.8 | ~277 kcal |
Source: Ainsworth BE et al. (2011) Compendium of Physical Activities
FAQ
- I have no idea how many calories I eat. What do I do?
- Pick the closest match in the breakfast, lunch, dinner, and snack menus and an estimate fills in automatically. If your weight has been stable lately, your actual intake must be roughly your maintenance calories, so pressing the maintenance button is the most accurate starting point. Work down from there.
- Where do I find my step count?
- The Health app on iPhone, or Google Fit or your smartwatch app on Android. Use your daily average over the last week or two rather than a single day's number, since weekends and weekdays differ a lot for most people.
- Should I enter my walk in both steps and workouts?
- No. That double counts it and overstates what you burn. Walks and commutes your phone already tracked are covered by the step count. Use the workouts section only for things steps miss, like weight training, swimming, or cycling.
- Why does this differ from the 3,500 kcal per pound rule?
- The 3,500 kcal rule is close enough for a few weeks but breaks down over months. As you lose weight your resting metabolism, your daily activity, and the cost of walking the same number of steps all fall, and metabolic adaptation lowers expenditure further. The daily deficit shrinks even though nothing about the diet changed. This simulator recalculates all of that every day, which is why the curve flattens the way real weight loss does.
- Can I still lose weight if I keep my weekly treat?
- Usually yes. A burger meal at around 900 kcal replaces a normal 600 kcal dinner, so the real addition is about 300 kcal, or roughly 43 kcal a day if you have it once a week. If your usual meals sit 200 kcal below maintenance, that treat still leaves you in a deficit. Change the count and compare.
- I am not losing as fast as this predicts. Why?
- Start by doubting the calorie estimate. Self-reported intake is underestimated by 20-30% in study after study (Lichtman SW et al., N Engl J Med 1992, among others). Drinks, cooking oil, sauces, and bites while cooking are the usual culprits. Logging honestly for one week finds the gap faster than adding more exercise.
- Why does the weight loss stall partway through?
- Plateaus are physiology, not willpower. Lose 5 kg and your resting metabolism plus daily activity burn roughly 100 kcal a day less, the same walk burns less, and adaptation cuts more on top. The model shrinks your deficit accordingly, so the line always levels off. When that happens, walking more is usually easier to sustain than cutting food further.