What a calorie deficit actually is
You're in a calorie deficit when you eat fewer calories than your body uses. Over time, a steady deficit is what leads to weight loss. A common rule of thumb is that about 7,700 kcal of deficit adds up to roughly 1 kg of body weight, though real bodies don't follow the maths exactly from week to week.
To know your deficit you need two numbers: calories eaten and calories burned. Logging food only gives you the first. NutriPixel gives you both, side by side, for every day.
How NutriPixel works out what you burned
Your daily burn has three parts, and NutriPixel counts each one exactly once:
- Resting. The energy your body uses just to keep running, worked out from your age, height, weight and sex with the Mifflin–St Jeor equation. For today, it counts only the part of the day that has passed.
- Digestion. Breaking down food uses energy too, about 10% of what you eat.
- Activity. Everything above resting: walking, workouts, moving around.
Activity is where the two modes differ:
- With Health Connect connected, NutriPixel uses the active calories your phone or watch recorded. If there are steps but no active-calorie data for a day, it estimates the burn from your steps, height and weight. It always trusts the measured data, even on a quiet day. It won't fill a lazy Sunday with activity that didn't happen.
- Without Health Connect, NutriPixel estimates your activity from the activity level you chose when you set up the app.
Your daily target
When you set up NutriPixel, it works out how much you burn on a typical day from your body and activity level. If your goal is to lose weight, your calorie target is set about 300 kcal below that. It's a gentle deficit that's easier to keep up than a crash diet, and the target never goes below 1,200 kcal. You can adjust it any time.
Earn back calories from extra activity
If you choose to, NutriPixel can add some of the calories from a more active day back to your budget. It only counts activity above what your target already assumes, so a normal day's walking isn't counted twice. You choose how much of that extra burn to earn back. It's off by default.
From daily balance to the weekly trend
A single day's balance is noisy. Water, salt and a late dinner can all move the scale. NutriPixel shows your balance each day and how it adds up over the week, alongside your logged weight. With Pro, you also get activity trends and insights, including your predicted weight change compared with what the scale actually did.
Keeping the numbers honest
Every figure here is an estimate. Fitness trackers can over- or under-count active calories, and photo estimates of meals can miss hidden oil. NutriPixel uses the same method every day, so even if the absolute numbers are a little off, the trend from day to day is meaningful. If your weight isn't moving the way the balance says it should after a few weeks, adjust your target.
You can make the eaten side more exact where it's easy. For anything in a pack, scan the barcode instead of taking a photo: NutriPixel logs the label's numbers for the serving you pick, and barcode scans are free and unlimited. Save photos for home-cooked and restaurant meals, where there's no label to read.