October 19, 2012

Dear Mayo Clinic:

I'm trying to lose weight, and a friend recently told me that cutting white bread and potatoes out of my diet completely will help. Is that true? If it is, what makes these foods so bad?

Answer:

Your friend is right. Taking white bread and white potatoes, as well as white rice and white pasta, out of your diet can be helpful for weight loss. Because of the way your body processes these four foods, they can lead to cravings for carbohydrates, also called sugars. By eliminating them, you decrease food cravings, making it easier to eat less and lose weight.

The grains in white bread, white pasta and white rice are refined through a milling process that strips off the bran layer to give them a finer texture. After that process, these foods are little more than carbohydrates that your body digests quickly and easily.

The main problem with white rice, bread, pasta and potatoes is that they trigger a cycle of food craving. After you eat them, they release a sudden spike of sugar in your bloodstream. Your body responds to that extra sugar by releasing insulin. Insulin is a hormone your pancreas makes that allows sugar to enter your cells, lowering the amount of sugar in your blood.

Because your blood sugar level goes up quickly after eating these foods, your body may release more insulin than it really needs. The extra insulin causes blood sugar to then drop lower than normal. When your body senses low blood sugar, you crave more carbohydrates. When you eat them, they once again raise your blood sugar, starting the cycle over. The result of this process is that you eat more food, more often.

In addition, as you eat more of these foods, your body needs to process all the extra sugar. Although some sugar is burned off as energy, most is converted into fat, leading to weight gain.

To get beyond the cycle of food cravings, I typically recommend to patients who want to lose weight that they completely avoid white bread, white rice, white pasta and potatoes for two weeks. After that, you can introduce them back into your diet in smaller, reasonable amounts.

Those two weeks can be hard because your body will have strong cravings for these foods. But during that time, the cravings should gradually decrease. Eating plant-based proteins such as nuts, beans and lentils can help. Lean meat and fish also can be good sources of healthy protein to include in your diet instead of rice, pasta, bread and potatoes.

Keep in mind, too, that the whole-grain alternatives of some of these foods can be healthy options if you eat them in moderation and keep portion sizes reasonable. Whole grains have not had the bran and germ removed through milling. They are better sources of fiber and other important nutrients, such as selenium, potassium and magnesium, than are refined grains. Whole grains can be single foods, such as brown rice and popcorn, as well as ingredients in other products, such as buckwheat in pancakes or whole wheat in bread.

Although avoiding white bread, pasta, rice and potatoes can be a useful step toward weight loss, it should be done as part of a healthy program that includes a balanced diet, along with exercise. For guidance on weight loss plans that may be right for you, consider meeting with a dietitian or talk with your doctor.

— Jon Ebbert, M.D., Primary Care Internal Medicine, Mayo Clinic, Rochester, Minn.

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