Going low carb involves making a lot of changes in your diet, and can also cause a lot of changes in how your body works. It is common for low carb dieters to experience changes in their bowel movements, especially during the first couple of weeks. Although most people do not notice any changes in their bowel movements, constipation is a frequent problem although some people suffer from diarrhea instead.
If you strain when having a bowel movement or don't go as frequently as you used to, it is probably because you eat less fiber than you used to, especially if you used to eat high carb and high-fiber breakfast cereals and whole grains. If your stools are dry, it is also very likely that you are not drinking enough water. Eating low carbs makes your body retains less water and excrete more water. If you become dehydrated when eating low carbs, it can not only cause constipation, but also headaches, fatigue and irritability.
You can get enough fiber in your low-carb diet without whole grains and legumes. Balance your low-carb diet with low-carb sources of fiber, especially nonstarchy vegetables. A generous serving of 1 to 2 cups per meal will help you get enough fiber in your diet to help things move smoothly in your gastrointestinal tract. For example, you can serve your scrambled eggs with red bell peppers and kale, your lunch can be based on a salad of fresh leafy greens, with tomatoes and avocado, and your dinner could be accompanied with Brussels sprouts and onions. You can also add flaxseeds, psyllium and wheat bran to your diet if you feel like you need extra fiber to prevent constipation.
Because eating low carbs can be diuretic and cause mild dehydration, drink at least eight to ten glass of water every day. Water is best, but you can also get the fluids you need from low-carb beverages, such as sugar-free coffee, herbal tea, tea or sparkling water. Adding a bit more salt to your food -- about 1/2 tsp. a day -- can help you retain more water in your body to prevent dehydration and infrequent bowel movements, as recommended by Dr. Eric C. Westman in "The New Atkins for a New You." Consult your doctor if you were told to limit your fluid or sodium intake.
A Word About Diarrhea
The most probably cause of diarrhea when eating low carbs is either lactose intolerance or a very high fat intake. Many low-carb diet programs recommend eating significant amounts of cheese and if you didn't use to eat dairy on a regular basis, your increased lactose intake could trigger diarrhea. Cut on the dairy if you suspect this is the problem. Alternatively, your diarrhea could be due to changing from a high-carb, low-fat diet to a low-carb, high-fat diet. If your body is not used to have a lot of fat, you may not be able to digest it properly. Cut down on your fat intake and increase your fat gradually to allow your body time to adjust and prevent problems with your bowel movements.