Short answer: 1 g of fat ≈ 9 kcal. That's more than twice the energy of 1 g of protein (4 kcal) or carbs (4 kcal). Whether we're talking olive oil, butter, avocado, lard, or MCT oil — the label always shows the same energy value per gram. Fat's energy density is a property of fatty acid chemistry, not of marketing.
In BiteNote you get a confidence range for the whole meal, but 9 kcal/g for fat is fixed. Worth knowing why.
| Fat source | Energy from fat (kcal/g) | Total energy (kcal/100g) | Fat (g/100g) |
|---|---|---|---|
| Olive oil | 9.0 | 884 | 100 |
| Butter, unsalted | 9.0 | 717 | 81 |
| Avocado, raw | 9.0 | 160 | 14.7 |
| Pork lard | 9.0 | 902 | 100 |
| Coconut oil | 9.0 | 862 | 100 |
Fats pack more energy per gram than proteins and carbs because the chemical structure of fatty acids contains many C-H bonds and little oxygen. C-H bonds release more energy when oxidized than C-O bonds (already partially oxidized, as in sugars). For comparison:
It's pure thermodynamics. Your body stores energy in adipose (fat) tissue rather than glycogen for exactly this reason — it packs 2.25× more kcal in the same gram.
Gross vs net value. The bomb calorimeter burns fat 100% and shows ~9.4 kcal/g (animal fats) or ~8.3 kcal/g (MCT). Atwater rounded to 9 kcal/g as the operational value for the whole category. The difference is small enough that it doesn't change calorie counting in practice.
Thermic effect of fat (TEF). Digesting fat costs ~3% of its energy — the lowest of all macros. From 100 kcal of fat you actually use ~97 kcal. That's why a high-fat diet provides less "thermic buffer" than a high-protein one.
No. Fat from avocado, salmon, olive oil, and nuts has the same 9 kcal/g as fat from butter, lard, or fries. "Healthy" refers to the fatty acid profile (monounsaturated, omega-3) and effect on lipid panels, not to calories. This is a common marketing misconception.
Two exceptions worth knowing:
📸 → BiteNote: salad with avocado, olive oil and chicken, ~480 kcal (445–510). Fat ~32g = 288 kcal from fat. Confidence: medium.
A tablespoon of olive oil (10g) is ~88 kcal — often the "hidden contributor" in salad calorie counts.
📸 → BiteNote: olive oil, 1 tbsp 10g, ~88 kcal. Confidence: high.
Per gram of fat — identical 9 kcal/g. The difference per 100g of product comes from butter's water content (~16%) and protein (~0.85g). Olive oil is pure fat (100g = 884 kcal); butter (100g = 717 kcal) is not 100% fat.
Yes, but slightly. Medium-chain triglycerides (C8, C10) have ~8.3 kcal/g vs 9.4 for long-chain. Nutrition tables round to 9. In practice, the difference between a tablespoon of MCT (~83 kcal) and olive oil (~88 kcal) is negligible.
Avocado (160 kcal/100g) has more calories than banana (90 kcal/100g) — that's a fact. But context: a typical half avocado (~70g) = 112 kcal, an average banana (~120g) = 108 kcal. The difference per realistic serving is small. "Gains weight" is too strong — daily calorie balance matters, not a single product.
Yes, both ~9 kcal/g. The difference lies in their effect on cholesterol and inflammation, not in calories. EFSA and AHA recommend most fats from unsaturated sources (olive oil, fish, nuts), but that's a health recommendation, not a caloric one.
The assumption was: since fat has 9 kcal/g (the most), cutting fat = easy deficit. In practice, replacing fat with sugar (low-fat = high-sugar products) didn't help. Modern consensus (EFSA, AHA): calorie balance and fat quality matter, not just fat quantity.
Log meals in 3 seconds on Telegram → @bitenotebot