Notes on tracking
what you eat.
How much water do you need a day? What the US values say
US reference values put total water near 3.7 liters a day for men and 2.7 for women, food included. What those numbers mean and where 8 glasses came from.
How much added sugar per day? The US and WHO limits
The new Dietary Guidelines cap added sugar at 10 g per meal, WHO says under 10% of calories, and labels use 50 g. What each number means and how to use them.
Photo, barcode, or search: which food logging method to use
Barcode, database search, photo, or a rough estimate? Where each food logging method gets its numbers, where it slips, and how to pick one for each meal.
How much protein do you need per day? Two US answers
The RDA says 0.8 g of protein per kg of body weight; the 2025–2030 Dietary Guidelines say 1.2–1.6 g/kg. What each number means and how to set a daily target.
How accurate are AI calorie counters from photos?
In 2025 studies, AI models looking at one meal photo missed calories by about 30–36% and macros by more. Where the error comes from, and how to log with it.
How accurate are nutrition labels? What the FDA allows
A packaged food can test up to 20% above its labeled calories before the FDA calls it misbranded. How labels are calculated, and what lab tests have found.
How far off are your calorie logs? What measured intake shows
Objective tests show people under-report calories by about 15% on recalls, and more on questionnaires. Why logging can still help, and how to read your numbers.