Legumes are often grouped together as high-carbohydrate foods, but the category is much more varied than that. Soybeans and lupins have a very different macronutrient profile from chickpeas, lentils and common beans.
Ranking per 100 g cooked
| Legume | Carbohydrate | Protein | Fiber |
|---|---|---|---|
| Mature soybeans, cooked | ~8.4 g | ~18.2 g | ~6.0 g |
| Lupins, cooked | ~9.9 g | ~15.6 g | ~2.8 g |
| Lentils, cooked | ~20.1 g | ~9.0 g | ~7.9 g |
| Kidney beans, cooked | ~22.8 g | ~8.7–9.5 g | ~7–9 g |
| Chickpeas, cooked | ~27.4 g | ~8.9 g | ~7.6 g |
Soybeans contain about 19 g less carbohydrate per 100 g than chickpeas in these references, a difference of roughly 69%.
Why soybeans are so different
Cooked mature soybeans provide about 18.2 g protein and 9 g fat per 100 g, alongside only ~8.4 g carbohydrate. Chickpeas and common beans allocate more of their dry matter to starch and other carbohydrates.
Lower carb does not automatically mean lower calorie
Cooked soybeans are around 172 kcal/100 g because they contain more fat, while cooked lentils are about 116 kcal/100 g despite having more carbohydrate. Fat provides about 9 kcal per gram, so it can shift total energy substantially.
Fiber is part of total carbohydrate
The table uses total carbohydrate. Some of that is fiber, which does not behave like digestible starch. Lentils, for example, have about 20.1 g total carbohydrate and 7.9 g fiber per 100 g cooked.
Serving size still matters
Per-100 g values are useful for composition, but real portions vary. A 150 g serving of cooked chickpeas would contain about 41 g total carbohydrate, while 150 g cooked soybeans would contain about 12.5 g.
Cooked weight is essential when comparing carbohydrate numbers
Legumes absorb a great deal of water during cooking, so dry and cooked database entries should never be mixed in the same ranking. One hundred grams of dry lentils contains far more carbohydrate and calories than 100 grams of cooked lentils simply because the cooked portion includes water. Canned beans add another wrinkle because the listed weight may include liquid while the nutrition panel refers to drained or undrained product depending on the label. A useful comparison uses the same ready-to-eat basis for every legume.
Most common beans and lentils are not low-carbohydrate foods in the way meat, fish or eggs are. What makes them nutritionally different from refined starches is that a substantial part of their carbohydrate comes with fiber and resistant starch, alongside protein and micronutrients. Someone following a strict ketogenic diet may still find the carbohydrate amount too high, while another person focused on blood glucose or satiety may value the fiber-rich package. “Lowest carb” does not automatically mean “best legume.”
The phrase “net carbs” can also create confusion. In the United States it is a marketing calculation rather than a single FDA-defined nutrient line. Companies often subtract fiber from total carbohydrate, and some products also subtract certain sugar alcohols. Plain legumes do not need that terminology to be compared: total carbohydrate and dietary fiber are both listed, allowing you to see the numbers directly. If you calculate net carbohydrate yourself, use the same method for every food.
Portion size changes the practical answer. Half a cup of cooked lentils or beans can fit into many meals even if the per-100-gram number looks substantial. Pairing that serving with non-starchy vegetables, protein foods and fats creates a very different meal from eating several cups of legumes plus bread or rice. The carbohydrate impact of a bowl depends on everything in the bowl, not merely which bean had the lowest database value.
Preparation matters too. Canned legumes are already cooked, while home-cooked beans can absorb different amounts of water depending on variety and cooking time. Puréed legumes may be eaten faster and in larger amounts than intact beans. Cooling and reheating can alter some starch structure, but it does not erase the carbohydrate. Use carbohydrate rankings as a portion-planning tool, not as evidence that a particular bean becomes a “free food.”
The practical takeaway
If you want legumes lower in total carbohydrate, soybeans and lupins sit far below chickpeas, beans and lentils. But protein, fiber, fat and calories should be considered too because the overall profiles differ sharply.
Sources
- USDA FoodData Central — Composition data per 100 g for cooked soybeans, lupins, lentils, kidney beans and chickpeas.