The short version: HabitSync shows you patterns in your own numbers. It doesn't practice medicine, and nothing here replaces a conversation with someone who does.
HabitSync's weight forecasts, BMR/TDEE estimates, calorie targets, and correlation insights are estimates, not medical advice, a diagnosis, or a substitute for guidance from a doctor, registered dietitian, pharmacist, or therapist. That matters most if you have a medical condition, take medication, or are pregnant or breastfeeding.
Calorie balance is the biggest single lever for most people, and it's what the calculator and forecast are built around. But it isn't the only thing moving the number on the scale. Sleep quality, stress and cortisol, hormones (thyroid function, PCOS, menopause), certain medications (some cause weight gain or loss as a side effect), muscle mass and body composition, water retention, menstrual cycle, age, and underlying medical conditions can all shift your weight independent of what you ate that week. Two people eating identically can lose weight at different rates for reasons that have nothing to do with willpower or math.
Treat every number here as a starting point for your own experimentation, not a guarantee. If your real-world results consistently don't match the estimate, that's useful information to bring to a doctor or dietitian - it isn't a sign you're doing something wrong.
The insights that surface things like "mood averages higher on gym days" are correlations found in your own logged data - they describe a pattern, not a proven cause. A pattern can exist for reasons other than the one that seems obvious, and small sample sizes (which every insight discloses) can produce patterns that don't hold up over time. Interesting, worth noticing, not a diagnosis.
Medicine tracking, dosage logging, and the before/after-onset chart are organizational tools to help you and your prescriber have a more informed conversation. They do not replace medical supervision. Never start, stop, or change a dose based on anything in HabitSync alone. If a photo-scanned label looks wrong, verify it against the actual packaging before logging it.
If you have a diagnosed medical condition, are on medication, are pregnant or breastfeeding, are under 18, or have a history of disordered eating, talk to a doctor or registered dietitian before using any calorie target or weight-loss timeline from this app or its free calculator.
HabitSync did not invent any of these formulas. Here is each one, what it does in the app, and where to read about it.
The default formula, and the one most dietitians reach for first.
What it does here: Your BMR on the calculator, and the resting burn behind your dashboard forecast, whenever Mifflin-St Jeor is the formula selected in Profile. It is the default, so this is the one most accounts are using.
Basal metabolic rate on Wikipedia
The calculator uses the 1984 revision, not the 1918 original. Both are listed so you can compare them.
What it does here: The same two places as Mifflin-St Jeor, your calculator BMR and your dashboard resting burn, when you select Harris-Benedict in Profile.
Harris-Benedict equation on Wikipedia
Works from lean body mass, which is why it asks for body fat. The equation comes from the McArdle, Katch and Katch exercise physiology textbook and builds on Cunningham's finding that lean mass predicts resting metabolism better than total weight does.
What it does here: Your BMR on the calculator and your dashboard resting burn when you select Katch-McArdle and have entered a body fat percentage. Without one, the app quietly falls back to Mifflin-St Jeor rather than guessing at your lean mass.
Basal metabolic rate on Wikipedia
TDEE is BMR times an activity factor from 1.2 (sedentary) to 1.9 (athlete-level training). That physical activity level approach is the one the FAO, WHO and UN University laid out for estimating daily energy needs.
What it does here: Turns your BMR into TDEE, the calories out figure on the calculator and in your pace breakdown. Once your daily burn has been measured from your own logs, this stops being used on a paid account: that number comes from your logged weight and calories instead.
Physical activity level on Wikipedia
The 3,500 calories per pound rule (7,700 per kilogram) is a simplification, and Hall's paper is why the timeline is labeled an estimate: the longer a diet runs, the less accurate that figure gets.
What it does here: Converts a calorie gap into weight per week. It sets the timeline on the calculator, the projected line on your weight forecast, and the weekly rate on the pace card. It is also how your daily burn gets worked backward from your weight trend.