| Calorie unit used in apps | Kilocalorie (kcal) |
| Calories per gram of protein | 4 kcal/g (Standard nutritional conversion factor) |
| Calories per gram of fat | 9 kcal/g (Standard nutritional conversion factor) |
| Low GI threshold | 55 or below (Glycaemic Index Foundation classification) |
| US % DV reference calorie level | 2,000 kcal/day (FDA Nutrition Labeling standard) |
Why the Terminology Matters
Opening a nutrition tracking app for the first time can feel like learning a second language. Terms like TDEE, net carbs, and glycaemic index appear in goal-setting screens, daily summaries, and food database entries — often without explanation. Misreading even one of them can lead to logging errors or misinterpreted progress.
This glossary defines the terms you are most likely to encounter, explains what each one measures, and clarifies how apps typically use the value. For a broader look at how macronutrients function in the body, see Macronutrients at a Glance.
| Calorie unit used in apps | Kilocalorie (kcal) |
| Calories per gram of protein | 4 kcal/g (Standard nutritional conversion factor) |
| Calories per gram of fat | 9 kcal/g (Standard nutritional conversion factor) |
| Low GI threshold | 55 or below (Glycaemic Index Foundation classification) |
| US % DV reference calorie level | 2,000 kcal/day (FDA Nutrition Labeling standard) |
Core Calorie and Energy Terms
Calorie (kcal). A unit of energy. In nutrition, "calorie" almost always means kilocalorie (kcal) — the energy needed to raise 1 kg of water by 1°C. Apps display food energy in kcal; the two terms are interchangeable in everyday diet tracking.
BMR (Basal Metabolic Rate). The number of calories your body burns at complete rest to maintain basic functions — breathing, circulation, and temperature regulation. Apps calculate BMR using formulas (such as Mifflin–St Jeor) based on height, weight, age, and biological sex.
TDEE (Total Daily Energy Expenditure). Your estimated total calorie burn over a full day, including physical activity. TDEE = BMR multiplied by an activity factor. Most apps use TDEE as the basis for your daily calorie goal. You can explore related calculators at Health Calculators.
Calorie deficit / surplus. A deficit means you consume fewer calories than your TDEE; a surplus means you consume more. Apps track this automatically once your goal is set. For a measured look at what logging these numbers actually reveals, see Calorie Logging: What It Can and Cannot Tell You.
BMR
Basal Metabolic Rate — the calories your body burns at rest to sustain vital functions. Calculated using height, weight, age, and biological sex.
TDEE
Total Daily Energy Expenditure — your estimated full-day calorie burn including all physical activity. Used by apps as the baseline for setting calorie goals.
Net Carbs
Total carbohydrates minus dietary fiber (and sometimes sugar alcohols). Represents the carbohydrates most likely to affect blood glucose.
Glycaemic Index (GI)
A 0–100 scale ranking how fast a food raises blood glucose compared to pure glucose. Low GI is 55 or below; high GI is 70 or above.
Glycaemic Load (GL)
GI adjusted for the actual carbohydrate content per serving. Provides a more practical measure of a food's real-world effect on blood sugar.
Macros
Short for macronutrients: carbohydrates, protein, and fat. These three nutrients supply all dietary calories and are the primary targets tracked in diet apps.
Micronutrients
Vitamins and minerals needed in small quantities for normal body function, such as iron, calcium, and vitamin D. Tracked in advanced app tiers.
% Daily Value (% DV)
A label figure showing how much one serving contributes to a standard daily nutrient target, based on a 2,000 kcal reference diet used in the US.
Macronutrient Terms
Macros (Macronutrients). The three primary nutrients that supply calories: carbohydrates (4 kcal/g), protein (4 kcal/g), and fat (9 kcal/g). Tracking apps let you set a macro split — for example, 50% carbohydrates, 25% protein, 25% fat — and display daily progress toward each target.
Net carbs. Total carbohydrates minus dietary fiber (and sometimes sugar alcohols). The concept reflects the idea that fiber is not digested and absorbed the same way as other carbohydrates. Not all apps display net carbs by default; some require this to be toggled on in settings.
Dietary fiber. A carbohydrate the body cannot fully digest. Soluble fiber dissolves in water; insoluble fiber does not. Both are tracked separately in many apps and count toward your total carbohydrate figure unless net carbs are displayed.
Sugar alcohols. Sweeteners (such as erythritol, xylitol, sorbitol) that provide fewer calories than regular sugar and affect blood glucose differently. Apps may list them under carbohydrates; how much to subtract when calculating net carbs varies by compound and individual response.
Complete vs. incomplete protein. A complete protein contains all nine essential amino acids (found in animal products and some plant sources like soy). Incomplete proteins lack one or more. Some advanced apps tag protein sources with this distinction.
For deeper context on each macronutrient's role, Nutrients & Food Groups covers the science in detail.
Glycaemic and Micronutrient Terms
Glycaemic Index (GI). A scale from 0–100 ranking how quickly a carbohydrate-containing food raises blood glucose relative to pure glucose. Low GI = 55 or below; high GI = 70 or above. Some apps display GI data alongside food entries, though the value is context-dependent — portion size, preparation method, and food combinations all influence the actual blood sugar response.
Glycaemic Load (GL). GI adjusted for the actual amount of carbohydrate in a serving. GL gives a more practical picture than GI alone. A food can have a high GI but a low GL if a typical serving contains very little carbohydrate.
Micronutrients. Vitamins and minerals required in small amounts — such as iron, calcium, vitamin D, and folate. Premium tiers of many apps track micronutrients, which can be useful for identifying dietary gaps. Always interpret low readings in context; app databases rely on food composition averages that may not match the exact item you ate.
App Databases Have Limitations
Food composition data in tracking apps is drawn from databases such as the USDA FoodData Central and user-submitted entries. Nutrient values are population averages and may not exactly match the specific item, brand, or preparation you consumed. User-submitted entries in particular can contain errors. Cross-check unfamiliar entries against the product's nutrition label where possible. For guidance on reading those labels, see Nutrition Labels Decoded.
% Daily Value (% DV). A reference figure on nutrition labels — and in many apps — showing how much a serving contributes to a standard daily intake benchmark. In the US, %DV is based on a 2,000 kcal/day reference diet. For a step-by-step label reading guide, see Reading a Nutrition Label Without Getting Confused.
4 kcal/g
Energy from carbohydrates and protein
Both carbohydrates and protein yield 4 kcal per gram — a standard conversion used by every major nutrition tracking app.
0–100
Glycaemic Index scale range
Pure glucose sets the benchmark at 100; all other carbohydrate foods are ranked relative to this reference point.
This article is for informational purposes only and does not constitute medical or dietary advice. Consult a qualified healthcare professional or registered dietitian before making significant changes to your diet or using tracked data to manage a health condition.