Diet Diary is a simulation game where you choose meals, exercise, and sleep for a pixel-art character each day and guide them to a goal weight. This page explains how to play, how to read the screen, and the events that can happen along the way. For how weight and calories are calculated, see How the Math Works.
1. Create your character
On the first screen, choose your character's sex, height, weight, age, goal weight, and job.
- Height is shown in feet and inches and weight in pounds (lb).
- The form starts with the average height and weight of U.S. adults in their 30s. Switching sex changes them to that sex's average.
- When you change the weight, the goal weight is set automatically to "weight − 7 lb." You can change it to any value afterward. The goal must be at least 1 lb away from your current weight.
- Your job sets how much you move during the day (activity level). Choose from desk job, on the go, on your feet, or manual labor.
- The top of the screen shows your character's body shape, along with BMI, weight category, and BMR (resting metabolism).
You can't set a goal weight that would put your BMI below 16. If the goal is below BMI 18.5 (underweight), you'll see a warning. This keeps the game from encouraging unhealthy weight loss.
2. Choose today's menu
Under "Today's menu," pick one option each for breakfast, lunch, dinner, snack, exercise, and sleep. Foods show their calories (kcal); exercises show their intensity (METs).
| Meal | Choices |
|---|---|
| Breakfast | Skip (0) / Yogurt (150) / Toast (300) / Eggs & bacon (480) / Muffin (450) |
| Lunch | Chicken salad (380) / Turkey sandwich (450) / Burrito bowl (700) / Cheesesteak (900) / Burger & fries (1,000) |
| Dinner | Veggie soup (300) / Grilled salmon (600) / Spaghetti (850) / BBQ ribs (1,100) / Pizza (1,300) |
| Snack | None (0) / Fruit (80) / Chips (330) / Cheesecake (450) / 2 beers (280) |
| Exercise | None / Walk 30 min / Jog 30 min / Weights 45 min / Swim 40 min |
| Sleep | 5 hours / 7 hours / 9 hours |
- Choose "Other" to enter your own food name and calories, or your own exercise name, intensity, and time. Try what you actually eat or the workouts you really do.
- Below the menu, you'll see your BMR, calories in, calories out, daily balance, and an estimate of how much your weight would change in one week at this pace.
- If your calories in are lower than your BMR, a warning appears.
You can change the menu at any time, even while the game is running. Changes take effect from the next day.
3. Start the diet
Press "Start diet" and the days advance automatically, one at a time. You can choose from three speeds.
| Speed | Time per day |
|---|---|
| Slow | 3 sec |
| Normal | 1.5 sec |
| Fast | 0.5 sec |
Press "Pause" to stop, adjust your menu, and then "Resume." There are also speed and pause/resume buttons below the Status panel.
4. Reading the screen
Status
- Day: how many days since you started
- Weight: what the scale shows that day. It goes up and down a little from day to day because of water weight and bloating
- BMI: a measure of body size, with your weight category (Underweight, Healthy weight, Overweight, Obesity)
- Change: how much your weight has changed since you started, and since yesterday
- Stress: 0–100. If it gets too high, you'll binge (see below)
- To goal: how many pounds are left to your goal weight. The bar below shows your progress
Character and scenes
Your character's body shape changes with BMI. The scene changes with the exercise you choose: a room with a floor lamp, a park with a city skyline, a gym, or a pool. On rainy days your character carries an umbrella. High stress gives a tired face, and steady progress brings a smile.
Weight chart
A line chart shows how your weight changes over time. The dotted line is your goal weight. Switch to "BMI" to see your BMI over time along with the healthy weight range (BMI 18.5–25).
Log
Each day's calories in and out, the balance, and anything that happened that day are recorded here.
5. Daily events
Just like a real diet, not every day goes according to plan.
- Day of the week: Day 1 is a Monday. On weekends you're more likely to skip exercise, and you snack a bit extra (150–400 kcal).
- Weather: Sunny 55%, cloudy 30%, rain 15%. You can't exercise on rainy days.
- Skipping: There's a 15% chance on weekdays and a 50% chance on weekends that you lose motivation and skip your workout.
- Short sleep: If you sleep 5 hours, you get hungry and snack (+150 kcal).
- Random events: Now and then, something happens: donuts at the office, happy hour with coworkers, taking the stairs because the elevator is out, a walk on your lunch break, or a friend asking, "Did you lose weight?"
6. Stress and binges
Stress goes up and down depending on your menu and your daily calorie balance.
| Raises stress | Lowers stress |
|---|---|
| Skipping breakfast / jogging or weights / sleeping 5 hours / cutting calories too hard (daily balance below −400 kcal) / eating less than your BMR | Snacks (fruit, chips, cheesecake, beer) / sleeping 7–9 hours / no exercise or walking / higher-calorie days (balance above +300 kcal) |
When stress reaches 85 or more, you'll binge the next day and eat 1,500 kcal extra. A binge brings your stress way down. It shows a real challenge of dieting: pushing too hard with strict cutting can backfire.
7. When you reach your goal
When your weight reaches the goal, a "Goal reached!" screen shows how many days it took, how much your weight changed, and how your BMI changed. You can share your result on X, send it through other apps on your phone (where your device's share menu is available), or copy the text.
After that, you can set a new goal weight and keep going, or start over from Day 1 with the same character and menu.
8. Saving your progress
Your progress is saved automatically in your browser. Next time, press "Continue" to pick up where you left off. Tap "Diet Diary" at the top of the screen during the game to go back to the first screen. Your data is never sent to a server, and it will be erased if you clear your browser data.
Tips
- A menu with a daily balance of about −300 to −500 kcal keeps stress low and your weight going down steadily.
- Cutting food too much raises stress, and your body goes into energy-saving mode, slowly lowering your BMR.
- Keep up strength training to build muscle and raise your BMR a little.
- Lowering stress with a snack or a good night's sleep is a valid strategy too.
Numbers in the game are estimates. Talk to a doctor or other health professional about real weight loss and health decisions.