Glossary
What is a food diary?
Updated 2026-08-16By Chris RichardsAll terms
Definition
A food diary is a running record of what and when you eat, kept so patterns become visible instead of remembered.
Definition
A food diary is a chronological log of meals, snacks, and drinks. A paper version records what and when; an app version attaches calories and macros to each entry and totals the day for you.
Reviews of behavioural weight-management research consistently identify self-monitoring — writing intake down — as one of the practices most often associated with better outcomes. The diary is the mechanism; the numbers are a by-product.
What a useful entry looks like
Detail beats completeness at first. "Chicken salad" tells you nothing next month; "180 g chicken thigh, 2 tbsp mayo, mixed leaves" can be re-logged in seconds and corrected later.
- Log before or during the meal, not at bedtime from memory.
- Weigh the things that carry the most calories per gram — oils, nut butters, cheese — and eyeball the vegetables.
- Record the days that went badly. A diary with holes in it cannot show you a pattern.
The mistake people make
Editing the record. A classic study using doubled-water measurement found participants underreported their intake by about 47% on average while overreporting exercise by about 51% — largely without intending to deceive anyone. Forgotten oil, unlogged tastes while cooking, and rounded portions do most of that damage.
A diary that only contains your good days is a diary of your intentions. The uncomfortable entries are the ones that carry information.
FAQ
What is a food log?
A food log is another name for a food diary: a chronological record of meals, snacks, and drinks. An app version attaches calories and macros to each entry and totals the day for you.
Paper or app?
Whichever one you will actually keep. Paper is fast and private; an app does the arithmetic, remembers repeat meals, and turns weeks of entries into a trend you can read at a glance.
Sources
- [1] Burke LE, Wang J, Sevick MA. “Self-monitoring in weight loss: a systematic review of the literature” (2011) — Journal of the American Dietetic Association 111:92–102 (PMID 21185970)
- [2] Lichtman SW, Pisarska K, et al. “Discrepancy between self-reported and actual caloric intake and exercise in obese subjects” (1992) — New England Journal of Medicine 327:1893–1898 (PMID 1454084)
General nutrition information, not medical advice. Calorie and macro targets are estimates — talk to a doctor or a registered dietitian before changing your diet, especially if you are pregnant, managing a health condition, or have a history of disordered eating.
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