The Down Low on Low-Carb Diets

How to avoid the pitfalls and side effects of a low-carb weight loss plan

By Colette Bouchez
WebMD Weight Loss Clinic - Feature

Reviewed By Brunilda Nazario

You've cleaned out those pantry closets, gone food shopping, and made the commitment. It's official: you're on a low-carb diet!

But while the road to a slimmer new you may be paved with high-protein foods, if you're like most low-carbers it's likely you've also encountered a few potholes along the way.

"Any time you make a fundamental change in your diet your body is going to react -- and when it does you are bound to experience certain symptoms or problems," says Stephen Sondike, MD, director of the Nutrition, Exercise, and Weight Management Program (NEW) at Children's Hospital of Wisconsin.

When that change involves reducing carbs, he says, among the most common problems is constipation.

"One of the primary places where you are going to see metabolic changes on any kind of diet is in your gastrointestinal tract -- and that can include a change in bowel habits often experienced as constipation," says Sondike, who is also credited with conducting the first published, randomized clinical trial on low-carb diets. The reason, Sondike tells WebMD, is that most folks get whatever fiber they consume from high-carb foods such as bread and pasta. Cut those foods out, and your fiber intake can drop dramatically, while the risk of constipation rises.

"However, if you really follow a low-carb diet correctly, you will be replacing those starchy foods with low-carb, high-fiber vegetables -- which should help counter the constipation by providing as much, if not more fiber, than you had before," says Sondike.

Doctors say that eating up to five servings of low-carb vegetables daily -- foods such as broccoli, cauliflower, and lettuce -- can keep your bowels healthy without interfering with weight loss.

If it's still not doing the trick, Sondike says a fiber supplement -- such as Metameucil or FiberCon can help.

"The one thing I would not do is start taking laxatives -- adding more fiber to your diet is definitely a smarter and healthier way to deal with the problem," says Doris Pasteur, MD, director of the Nutrition Wellness program at Mt. Sinai Medical Center in New York City.

A low-carb diet can help you lose weight because it turns on fat-burning processes, known as "dietary ketosis." These ketones are also thought to have an appetite suppressant effect.

However, Pasteur says that when large amounts of ketones are produced, your body can become quickly dehydrated -- another problem faced by those on a low-carb diet.

The solution: Drink more water.

"The lower your carb intake, the greater your risk of dehydration and subsequently the greater your need for water," says Pasteur. Most low-carb diet experts suggest drinking at least 2 quarts of water daily.

In addition to keeping you adequately hydrated -- which can also help alleviate constipation -- drinking lots of water can also help offset still another low-carb diet problem: bad breath. The ketones produced during the diet can lead to what is sometimes described as a fruity odor although it is often described as having an almost "chemical" odor similar to acetone or nail polish remover.

Now if you're thinking you'll just handle the problem by brushing and flossing a little more often, guess again. Since the breath odor is coming from metabolic changes and not necessarily a dental-related condition, traditional breath products are not likely to provide long-lasting relief. On the other hand drinking more water intake can do the trick.

"The water helps dilute the ketones in your system, and while that won't affect weight loss, it will help with the bad breath," says Sondike.

Low Carbs and Supplements

The lower your intake of carbohydrates, the greater your need for a vitamin supplement. That's the mantra that most doctors now recommend that everyone on a low-carb diet should never forget.

The reason? Any time you restrict your diet, particularly in terms of certain food groups, your nutrient levels can drop. But when your diet is low carb, experts say you may be in even greater need for certain key vitamins and minerals, particularly folic acid.

"If you're cutting out cereals, fruits, vegetables, fortified grains, then you are cutting out your major source of folic acid, a B vitamin that is not only important when you are pregnant, but important to everyone's overall health," says NYU nutritionist Samantha Heller.

What's more, says Heller, folic acid is key to controlling levels of homocysteine, an inflammatory factor linked to heart disease. If you're already at risk for cardiovascular problems, she says, dropping folic acid levels too low could put your health at serious risk.

One way to protect yourself, she says, is to take a B vitamin supplement -- with at least 400 micrograms of folic acid daily.