Diabetes Forecast

Navigating a Low-Carb Eating Plan

Some people are giving up bread, potatoes, and pasta in pursuit of better health. Should you?


Story updated May 5, 2017

If you ask a dozen people, including medical professionals, to define a low-carb diet, you’ll likely hear 12 different answers. For some, it’s an eating plan that swaps refined grain products (such as white pasta) with their whole-grain cousins (such as whole-wheat pasta). Others say such a diet demands that you give up cereal, bread, potatoes—and other carbohydrate-rich foods—altogether.

On the surface, it seems that a diet lower in carbohydrate—the nutrient that has the biggest effect on blood glucose levels—would benefit people with diabetes, who need to manage those levels for optimal health. Cutting carbohydrate, particularly when it comes from sugar and refined grains, can help people with diabetes manage weight and their blood glucose. But the notion of a low-carb diet is poorly defined and commonly misunderstood.

“When people tell me they are following a low-carb diet, they are usually still eating fruit, dairy, beans, and even whole grains—in other words, not low carb at all,” says Lori Zanini, RD, a registered dietitian based in Manhattan Beach, California, and a spokeswoman for the Association of Nutrition and Dietetics. To give you an idea of how carbs add up, consider that a medium apple has 25 grams of carbohydrate, a serving of cannellini beans (1/2 cup) has 18 grams, a serving of canned corn (1/2 cup) has 9 grams, and a small slice of whole-wheat bread has 15 grams.

“For people with diabetes, I define low carb as less than 120 grams a day,” says Jessica Crandall, RD, the wellness director at food-service company Sodexo in Denver. That number isn’t arbitrary; Crandall says this recommendation has been established through research as well as her own experience with adult clients. She says that 120 grams of carb per day provides adequate glucose to fuel your brain. 

But your brain doesn’t need to get it all from carb sources, says William Yancy, MD, associate professor of medicine and director of the Duke University Diet and Fitness Center in Durham, North Carolina. On a strict lower-carb eating plan—say, somewhere around 20 or 50 grams per day—the brain will get glucose from alternate sources, such as through the breakdown of protein and fat.

Burning fat for fuel produces ketones—not to be confused with the surplus present in diabetic ketoacidosis (DKA), a condition caused by too little insulin and too-high blood glucose. The body resorts to burning fat for fuel, which produces large amounts of harmful ketones. If left untreated (IV insulin and fluids are the typical treatment), DKA can lead to coma and even death. While the lower levels of ketones produced on very low-carb diets aren’t dangerous in the way DKA is, they can cause an unusual side effect: Your breath and sweat may smell like ammonia or nail polish remover.

The Controversy

After you eat, your body breaks down the food so the glucose can find its way into your bloodstream. From there, insulin ferries the glucose into the cells, where it will be used for energy. In type 1 diabetes, the pancreas can’t make insulin, so the glucose sticks around in the blood, unless insulin is injected. In type 2, the body makes insulin but is unable to use it properly (what’s known as insulin resistance), forcing the pancreas to work extra hard to pump out more insulin. Eventually, the body can’t keep up with the demand, and high blood glucose results.

In both cases, it would seem logical to drive blood glucose down as much as possible with diet, which leads some people to adopt a strict low-carb diet. But whether that way of eating is healthy and doable for a lifetime is the subject of debate.

Since Robert Atkins, MD, popularized the low-carb weight-loss diet by telling followers to eat bun-less cheeseburgers and piles of bacon, people have been trying to lose weight and get healthy the low-carb way, with decidedly mixed results. But any diet that puts an emphasis on foods with saturated fat has the drawback of potentially increasing your risk of heart disease and cancer, which is associated with greater processed meat consumption. More moderate low-carb plans have emerged over the years, but they often cut out whole grains, starchy veggies, and fruit—food groups with significant health benefits of their own.

The American Diabetes Association (ADA) does not advocate for or against a low-carb eating plan, but it does recommend reducing saturated fat. Its 2017 Standards of Medical Care in Diabetes recommends emphasizing in a meal plan unsaturated fats found in plant-based foods, such as oils, nuts, and avocados.

Curbing your saturated fat intake can be tough when you cut carbs, because people tend to replace carb-containing foods with meat and cheese—most of which are high in saturated fat and lack fiber and certain vitamins and minerals. A low- or lower-carb diet, the way it’s commonly practiced, often means eating fewer fiber-rich foods such as whole grains and beans, which are associated with health benefits, including reducing cholesterol. This is in large part why low-carb eating stirs controversy and why some registered dietitians advise against it.

Low-Carb Cons

There are many reasons to proceed with caution if you are considering a low-carb diet. If you are on insulin, suddenly restricting your carbohydrate intake can cause lower blood glucose.

“The biggest con for me is the question of longevity. How long can most people really follow a strict low-carb plan?” says Crandall. When you think about family dinners, holiday celebrations, and birthday cake, it’s easy to see how very restrictive eating plans can socially isolate a person. And then there’s the cooking: Most prepared, packaged, or convenience foods contain plenty of carbs, even if they’re rich in whole grains, so low-carb devotees will likely need to make most of their meals.

People often lose weight on low-carb diets, “but people lose weight on any elimination diet,” says Crandall, referring to eating plans that restrict overall calories or food groups. “But what I usually see with this is someone loses 40 [pounds] and then gains back 50 when they can’t sustain it anymore.”

Without the fiber provided by carb-rich foods such as beans and whole grains, constipation can be an issue. Of course, eating nonstarchy vegetables is a lower-carb way to get enough fiber. Also, many people on low-carb diets complain of low energy and—even worse—muddled thinking. “The glucose you get from healthy carbs is your brain’s preferred fuel source,” says Crandall.

Even advocates for lower-carb eating for some people with diabetes offer words of caution. “We don’t understand the long-term health consequence of saturated fat consumption [specifically in people with type 1 diabetes],” which people often eat more of when they cut carbs, says Jake Kushner, MD, a professor of endocrinology at Baylor College of Medicine in Houston, Texas. “There’s a real deficit of research. We need controlled studies.”

Low-Carb Pros

Still, Kushner says he has countless anecdotes of people with type 1 diabetes who have benefitted from cutting a considerable number of carbs. “As you get below a certain threshold [of carbohydrate consumption], glucose control becomes much more predictable,” he says.

Critics say there’s a risk for people with diabetes to have serious lows when starting a low-carb eating plan without adjusting medication. Proponents say restricting carbs could have the opposite effect. “Lowering carbohydrate intake allows people with diabetes to reduce their insulin dose,” Yancy says. “And lower insulin doses mean lower risk for hypoglycemia.”

Most experts who support a low- or lower-carb diet promote a way of eating that’s less of a bacon free-for-all and more balanced. They encourage people to eat plenty of nonstarchy vegetables, such as broccoli, peppers, and tomatoes, and to prepare salads with healthy fats like olive oil. Lean proteins, such as fish, are on the suggested menu.

Paul Loftland, 69, a retired maintenance worker, signed up for a low-carb weight-loss clinic in the hopes of losing weight and taking control of his type 2 diabetes. At first, he never thought he’d be able to stick with the food plan; it contradicted the low-fat, grain- and cereal-rich diet advice he’d heard all his life. But soon after joining the program and limiting his carb intake to 30 grams a day, his blood glucose and cholesterol had improved, and he was able to come off his metformin and cholesterol medication.

Loftland’s results may not be all that surprising. A 2015 study published in The American Journal of Clinical Nutrition that compared low- and high-carb diets suggested that a low-carb eating plan could be an effective way for those with type 2 diabetes to improve their glucose control, though the study indicated that more research is needed.

The challenge of any eating plan is that, if daily carb totals increase or other changes occur, such as weight gain or less physical activity, the need for medication may return. That’s why Loftland has remained vigilant. “When I started at the clinic, my A1C was 8.7 [percent]. Today it’s 5.1,” says Loftland, who’s lost roughly 50 pounds. So what’s on his meal plan? Omelets for breakfast, salads for lunch, and lean protein and greens for dinner—choices he expects to make for the rest of his life.

Tips for Making the Switch

What’s important to remember when considering a lower-carb eating plan is that you and your doctor—and, ideally, a dietitian—can customize the plan to fit your lifestyle and needs. For many, reducing carbohydrate and choosing the right kind of carbs, such as moderate portions of fiber-rich beans, sweet potatoes, and whole grains, plus lots of nonstarchy vegetables, is enough to make a big improvement in their health.

But be careful: When you are switching to a lower-carb way of eating, particularly if you are on medication, blood glucose can rapidly drop too low. Regular blood glucose checks and a trusted health care provider’s advice are both extremely important.

Vicki Curran of Warminster, Pennsylvania, who has type 2 diabetes, cut packaged snacks and white pasta from her eating plan after she took a nutrition class for people with diabetes at her local hospital. She lost about 50 pounds when she changed the way she ate, and has kept it off for the past six years. Her A1C level is down from 8 percent at the time of her diagnosis several years ago to 5 percent. Her doctor is planning to take her off metformin in the coming months if her A1C stays in this range. And Curran still enjoys her favorite food, pasta. “I used to eat white pasta at least once a week. Now I still eat pasta, but it’s always whole wheat, and usually I have it about once a month,” she says

Here’s an approach to a lower-carb way of eating: “Cut the liquid sugar first—soda, juice, coffee drinks—and then go for the refined white carbs,” says Zanini. For example, cut out cookies, cake, and white pasta. And as you look for foods to curb or cut out, be careful about what you’re replacing them with. “Make sure you are getting enough fiber by increasing those nonstarchy vegetables and eating some nuts and seeds,” she says. Chia and flax are her favorites to sprinkle on foods.

Meal Plan

If you decide a lower-carb eating plan is something you want to try, smart meal planning is a must. Replace carbs with healthy alternatives and make sure portion sizes are appropriate. For most carb-rich foods (even the healthy, complex carbs in whole grains and beans), you’ll want to keep it to about ½ cup per serving.

Generous amounts of steak, cheese, and bacon are often touted as perks of a low-carb program, but limiting saturated fat is also important for healthy eating. Lean protein sources, including skinless chicken and fish, should play a bigger role in your low-carb meals than foods that are processed or are high in saturated fat.

Nonstarchy vegetables including asparagus, bell peppers, broccoli, brussels sprouts, cabbage, cauliflower, and leafy greens, among others, should continue to occupy major real estate on your plate at most meals. A good guide? Fill half the plate with nonstarchy veggies. All healthy approaches to a low-carb plan—or to any healthy eating plan—will mean you are eating more vegetables, not less.

Still not sure whether a low-carb diet is right for you? Talk over your options with your health care provider, who can help you weigh the pros and cons and determine how they fit into your lifestyle and diabetes management. In the end, the best eating plan isn’t moderate or low carb—it’s a healthy plan you can stick with.



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