Onion
A low-glycemic aromatic vegetable with almost no effect on insulin.
FatTonic Facts
Onion · per serving 1 medium (110g)
Excellent · strongly supports fat-burning
| Factor | Amount | Points |
|---|---|---|
| Start | 100.0 | |
| Glycemic load | 1 | −2.2 |
| Sugar (g) | 5 | −4.0 |
| Processing | whole | 0.0 |
| Fiber (g) | 2 | +3.2 |
| Protein (g) | 1 | +0.7 |
| Glycemic index | not tested | |
| Carbs (g) | 11 | |
| Fat (g) | 0 |
Score model v1
Nutrients: USDA FoodData Central, record 170000 (Onions, raw), public domain, checked 2 Oct 2026.
Glycemic index: not tested — too little carbohydrate to test (University of Sydney GI FAQ); the score assumes 15.
Per 100 g (USDA record; serving 110 g): carbs 9.3, sugar 4.2, fiber 1.7, protein 1.1, fat 0.1 g.
What this means for fat-burning
Why this score: sugar 5 g set it, −4.0 points. Source: USDA FoodData Central, FDC 170000.
See how your whole day scores — free Metabolic Score →This food and 199 more, scored on your phone.
Among the 200 rated foods
Onion scores 98, rated Excellent. It scores higher than 71% of the 200 rated foods.
Rated foods per band: Avoid 0–19: 11; Poor 20–39: 23; Moderate 40–59: 34; Good 60–79: 45; Excellent 80–100: 87.
Frequently asked questions
Does onion spike insulin?
Glycemic load 1 for 1 medium (110g); FatTonic Score 98/100 — it strongly supports fat-burning.
Is onion good for fat loss?
Excellent (98/100): onion strongly supports fat-burning.