Complex carbs (polysaccharides or oligosaccharides) have three or more sugar molecules. Compared to simple carbs, complex carbs are more slowly absorbed into your bloodstream.
Examples of complex carbs include:
- Parsnips and starchier veggies
- Legumes and beans like chickpeas and kidney beans
- Whole grains like bread, breakfast cereal, rice, and quinoa
What About Low-Carb Grains?
Some keto professionals and advocates believe grains, in general, aren’t suitable for a ketogenic diet. In contrast, others say it depends on the grain, how often you eat it, and the person. People who are more fat-adapted may be able to remain in ketosis while consuming some grains. Fat adaptation means your body is metabolically equipped to handle digesting fat instead of carbs and smoothly switching between the two fuels.
You need to assess the net carb count of low-carb grains instead of the total grams of carbs to determine whether you should include low-carb grains in your diet. In smaller amounts, you might be able to have some lower-carb grains and stay in ketosis.
Since fiber doesn’t affect your blood sugar levels, you want to go for grains that have some fiber and are lower in carbs.
Bulgur is a cereal grain typically derived from cracked wheat berries and used in dishes like tabbouleh and porridge. 1 cup (182 grams) of cooked bulgur has 25.5 grams of net carbs, making it one of the lowest carb whole grains around. 
Millet is an ancient grain, and 1 cup (174 grams) of cooked millet provides 39 grams of net carbs and over 2 grams of fiber. 
Quinoa is a pseudo-grain often prepared and served as a grain. 1 cup (185 grams) of cooked quinoa provides 34 grams of net carbs, so it may not be suitable for many keto dieters.  
Couscous is a processed grain product and a Moroccan staple dish. 1 cup (157 grams) of cooked couscous provides around 34.5 grams of net carbs. 
You might be surprised to think of popcorn as a grain, never mind a lower-carb grain, but a 1 cup (14 grams) serving of popped popcorn actually only has 6.5 grams of net carbs. Check the label to make sure there aren’t any added sugars and, ideally, opt for air-popped popcorn. Keep in mind popcorn may not be the healthiest snack choice as it usually comes along with trans fats and artificial ingredients. 
Wild rice comes from specific grasses in the Zizania genus of plants. Wild rice isn’t related to true rice (oryza sativa). 1 cup (164 grams) of cooked wild rice provides 32 grams of net carbs. 
Ezekiel bread is a sprouted ancient grain bread containing organic grains and legumes, including soybeans, lentils, millet, wheat, and barley. Some people might be able to incorporate one slice of Ezekiel bread on keto. 
Off-Limits High Carb Grains
Grains that are less processed and refined also usually have a lower carb content. Some grains and refined grain-based products have a much higher carb count and are lower in fiber, making them off-limits on keto, such as:
- White bread
- Refined pasta
- White rice
- Grain-based breakfast cereal
- Pizza dough
- Instant oatmeal
- Wheat flour muffins and cakes