Rice, noodles and steamed buns are staple foods, rice is rice, while most of the noodles and steamed buns are wheat flour made of pasta, rich in starch, the same calories. If you insist on comparing, you must also look at the amount of dietary fiber, the rate of rise of sugar, and what foods you eat together. When we eat rice, we usually eat it with meat and vegetables. White rice is not swallowed by anyone. Even if there is no food, no meat, we serve it with squash. The same goes for steamed buns. If we use it instead of rice as a staple food, we have to take a bite of steamed bread and a bite of food to taste the flavor.
In contrast, noodles are different. Noodles are usually the star of the show, while meat and vegetables are the proper supporting cast. A few pieces of meat and a couple of vegetables can call for a bowl of noodles. So relatively speaking, we may eat more starch while ignoring other nutrients, one affects blood sugar, and the other is easier to get fat by eating a bowl of noodles. It is recommended to eat noodles with more meat dishes, so that the noodles become a supporting role.
Buns and rice are usually good staples, they can quickly increase sugar. If you want to lose weight, it's best to opt for optimization. For example, adding some coarse grains and mixed beans to refined white rice can increase dietary fiber intake, add more minerals, stabilize postprandial blood sugar, and inhibit the absorption rate of fat, cholesterol, and sugar for multiple purposes. For buns, whole wheat flour, buckwheat flour, coarse grain flour can also be used to make coarse grain buns, but the process is somewhat complicated, many stalls claimed coarse grain buns are not in fact coarse grain buns, is still flour and rice to do, just coloring with a small amount of bran. So if you compare, rice is better for weight loss. I'm sure anyone can do it with couscous and rice.
But, finally, it must be stated that the staple food is not these three. We can also choose starchy fruits, starchy nuts and potatoes as staple foods, which are more natural, less processed, retain more nutrients and dietary fiber, and are more suitable for weight loss. Staple foods suitable for blood sugar control and weight loss are mainly coarse grains, rich in dietary fiber, which can improve satiety and nutrition. Of course the staple food is suitable, depending on how to control the total calories. Weight loss is not easy.