How Kexo learns your calorie needs

The idea is simple

Your log shows energy in. Your weight trend shows whether stored energy is going up or down. Put the two together and you can estimate how much energy you use. Kexo keeps the original formula, then adds a small weekly adjustment. The coach explains the number. It does not invent a new target in chat.

Whether you use a photo, text, voice, a barcode, or a manual edit, the calculation sees the same thing: what you ate.

Why 21 days

Weight jumps around from one day to the next because of water, salt, training, and digestion. Three weeks smooths out some of that noise without waiting forever. We have not proved that 21 days is better than 14 or 28. It is our current choice, not a scientific winner.

What counts as enough data

• A day that counts: at least 2 meals logged, or at least 1,000 kcal that day. A lone coffee does not count and does not drag the average down. Two small snacks do count, and they pull the average down.
• Minimum: 10 days that count in those 21 days.
• Weigh-ins: at least 3 logs, with the first and last at least 10 days apart. Kexo draws a simple trend through them and does not remove outliers. When weigh-ins are sparse, one salty dinner can skew the trend.
• First update: Kexo cannot change the target until those conditions are met. This can happen around day 10 to 14, not only after day 21.

How far the target may move

People often log less than they eat. That can pull the estimate down and make the food budget too small, which is the riskier direction. So Kexo can raise the target faster than it can lower it:

• At most 150 kcal up in a week, or 100 kcal down.
• The whole correction stays inside +25% / −15% of the starting estimate.
• A move under 50 kcal leaves the target as it is.
• Changes are rounded to the nearest 10 kcal.

Kexo does not secretly add calories to your meals. The adjustment only controls how far and how fast the weekly target can move.

When Kexo leaves the target alone

If you did not log enough days or barely weighed in, Kexo waits. It also ignores a week when the estimated burn looks far too low or far too high next to your resting calories. In both cases, last week’s target stays.

After four weeks in a row without a useful update, the old adjustment starts moving back toward the formula by about 50 kcal a week. Keeping an old number forever would look like Kexo is still learning when it is not. You can also turn the feature off in settings. Then the target never moves.

The 1,200 kcal floor

Kexo will not set a normal rest-day target below 1,200 kcal. That is a safety floor in the app, not a claim that 1,200 kcal is medically right for everyone. NIDDK’s Diabetes Prevention Program materials advise against going below about 1,200 kcal in that program. NICE guidance from 2025 treats 800–1,200 kcal a day as a low-energy diet that belongs under specialist support. Kexo is not that setting. See also Safety.

A simple example

Starting estimate 2,000 kcal. You logged about 1,900 kcal on the days that count. Weight is drifting down about a third of a kilo a week. That implies you are burning closer to 2,285 kcal. The first week can only add 150, so the target steps up by 150. A second similar week can add another step. When the remaining gap is under 50 kcal, the target stays put.

Where it can go wrong

• Logging in fits and starts. Missed weeks leave you on an old target, or one that is moving back to the formula.
• The first two weeks. You are on the formula. Nothing has been learned yet.
• A fast drop in the first days (often water, not fat). That can make the app think you burn more than you do, and upward changes can happen faster. Waiting for enough data is the current safeguard.
• Medication that changes appetite or weight quickly. Kexo does not adjust for any medication. Talk to the clinician who prescribed it. See Safety.
• Half-logged days treated as full days. Two small entries make the day count. If dinner is missing, Kexo cannot know.

The limits

• We do not claim a measured accuracy for the learned calorie need. A proper test is being prepared, but there are no results yet.
• We do not claim this is your true lab-measured expenditure. Logging error remains part of the number.
• We do not claim 21 days is better than 14 or 28.
• This is not medical advice. Kexo is not a medical device.