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Can cutting out carbs be the secret to losing weight and balancing blood sugar? I talked to a diabetes expert to find out.

Jaime Ritter
August 29, 2018

My fiance, Nick, and I recently tried out the keto diet. We had two very different experiences: You can read all about it here. But suffice to say that, while I didn't find it so useful, he loved it.

One of the biggest things he loved is what it did for his blood sugar. He’s a type 1 diabetic (the kind you're born with), and his typically high blood sugar average (as measured over a three-month period—often called a1c) went down an entire point. If you don't know much about diabetes, this is a huge deal: Prolonged elevated blood sugar levels can lead to scary things like nerve and organ damage over time.

But I started to wonder: How healthy (or safe) is the keto diet for people with diabetes? I mean, Nick's numbers (after just three weeks!) were astounding. So, if it's healthy, why aren’t doctors recommending that all diabetics eat super low-carb? And if it's not healthy, what are the risks?

I turned to diabetes and nutrition expert Jill Weisenberger, a registered dietitian and author of three books on diabetes, including Diabetes Weight Loss—Week by Week, to find out.

Spoiler alert: Weisenberger is not a huge fan of the keto diet. In fact, when I first broached the subject, she referred me to a statement from the American Diabetes Association that says, essentially, that the jury is still really out on whether a low-carb diet helps, and that at best, it's really hard to keep up over the long term. Here's the quote in full:

“The role of low-carbohydrate diets in patients with diabetes remains unclear. Part of the confusion is due to the wide range of definitions for a low-carbohydrate diet. While benefits to low-carbohydrate diets have been described, improvements tend to be in the short term and, over time, these effects are not maintained. While some studies have shown modest benefits of very low–carbohydrate or ketogenic diets (less than 50g carbohydrate per day), this approach may only be appropriate for short-term implementation (up to 3–4 months) if desired by the patient, as there is little long-term research citing benefits or harm.”

Still, I wanted to know what was up with Nick's numbers, and what the potential problems were. Here's what Jill had to say:

Keto Isn't Always Keto

Weisenberger says, “Many times when the average person [says they] follow a keto diet, they’re not actually in ketosis. They’re just following a low-carb or very low-carb diet.” The problem? Research studies are confusing and often impossible to compare because low-carb diets don’t have a strict definition the way that low-fat diets do.

Weisenberger says most people with diabetes report getting 44-46% of their total calories from carbs. “That’s not a prescription, that’s just what most people with diabetes report. In one study, she says, “low-carb could mean 20g a day, while other times it means 50 percent of your daily calories.”

Nick and I followed the keto diet for three weeks. We religiously counted our net carbs through an app and limited them to between 20-50g a day. Nick didn’t test his ketones, but I did. According to my test strips, it took me about five days just to get into ketosis, and I fluctuated in and out over the three-week period. So I can say for certain that staying in ketosis is really difficult.

I'm fairly certain we were both in ketosis, however: Nick and I both experienced the traditional side effects (namely keto flu, serious carb cravings, and quick weight loss).

And I'll say that I would definitely find it hard, if not impossible, to keep up long-term. But Nick was inspired to keep going, and as of this writing, he’s been on keto for almost two months.

Variety Is Especially Important for Diabetics

Weisenberger allows that the ketogenic diet can help you lose weight, but notes that it eliminates a number of essential food groups for diabetics such as whole grains, starchy vegetables, and most fruits.

“My concern," she explains, "is when we take away a large number of wholesome foods, you’re not getting nutrients for disease prevention. We are eliminating the exact foods that we know help prevent heart disease, cancer, and help dial back insulin resistance.”

On the diet, Nick and I tried to stay balanced with nuts, plenty of veggies, and of course meat and dairy, but we weren’t on it long enough to know whether it was having an affect on our risks for heart disease or cancer.

Keto and Gut Health

Non-ketogenic foods like fruit, whole grains, and legumes aren’t just helpful for disease prevention—they’re also good for your gut. Weisenberger says, “Good bacteria feeds on various types of carbohydrate-containing foods.”

A healthy gut microbiome can help tamp down inflammation, a problem that many people—but especially diabetics—suffer from. One way to achieve a healthy gut is to eat plenty of fibrous foods—which means not restricting carb-containing food groups, according to Weisenberger.

She says, “The least restricted diet is going to be the most wholesome. I don’t mean eating jelly beans and pretzels all day, but if you have a selection of 10 wholesome foods or 100 wholesome foods to choose from, it’s going to be better to have the larger selection.”

Keto and Cholesterol

Of course, one of the best things for good gut health is fiber—which also reduces cholesterol. But it's easy to miss out on enough on the keto diet. I, for one, definitely struggled here (I’ll spare you the details).

Dr. Marcelo Campos, a lecturer at Harvard Medical School, wrote on the Harvard Health blog that “a few studies show some patients have [an] increase in cholesterol levels in the beginning [of a keto diet], only to see cholesterol fall a few months later. However, there is no long-term research analyzing its effects over time on diabetes and high cholesterol.”

Normally, I get a lot of fiber from fruit, but that's definitely hard to fit in, since it contains so many carbs and natural sugar. I found if I was strategic with carb-counting I could eat a small portion of berries each day. That being said, I definitely couldn’t eat as much produce as I wanted to, and I really missed eating healthy things such as bananas, black beans, and sweet potatoes.

All those cholesterol-lowering foods are extra important because diabetics are more likely to have higher levels of “bad” cholesterol and are at a higher risk for heart disease and stroke. Research shows that eating a diet high in produce, healthy fats, low-glycemic carbs, and lean meats could reduce risk of heart disease and stroke by up to 40 percent.

The confusing part? Though a keto diet doesn’t include a few of those food groups, it isn’t necessarily detrimental to cholesterol levels. But there’s not enough research to show it’s helpful, either.

Unfortunately, Nick's only been on the keto diet for a few months, so his doctor hasn’t been able to measure his before-and-after cholesterol levels just yet. He has high cholesterol, and he’s on medication for it, so he gets measured pretty frequently—I’ll keep you posted on his results.

Why Diabetics Need Carbs

I thought that eliminating carbs (or at least limiting them) would be better for diabetics, but Weisenberger says that’s not necessarily the case. She says carbohydrate control is “paramount for blood sugar control”, and that carbs provide necessary nutrients and fiber for people with diabetes.

I was confused by the idea that carbs “help” to control blood sugar since, in my mind, carbs and sugar drive up blood sugar levels.

In fact, when Nick and I did the keto diet his blood sugar leveled out so much that his doctor had to adjust the basal insulin in his pump to match his consistently lower blood sugar.

Weisenberger said that she doesn’t solely credit the keto diet for Nick’s lower blood sugar. She says, “I think cutting carbs dramatically would result in lower A1C, whether or not he was in ketosis.”

She also said that even if Nick’s blood sugar was lower on a keto diet, there still could be underlying issues. She says, “We can tamp down blood sugar without addressing other problems such as insulin resistance, less insulin production, high amounts of glucagon, and hormone imbalance.”

One way to address those issues? Eating a balanced diet—including some fruit, veggies, and, yes, carbs.

However, that doesn’t mean you should reach for French fries and brownies. Weisenberger suggests eating low-glycemic, high-fiber foods. This includes foods like beans, oats, apples, and barley—which are healthy, but not part of a keto diet.

The Bottom Line

Research seems to be mixed on the benefits of a keto diet for diabetics, but experts like Jill and the American Diabetes Association both recommend eating a balanced diet full of lean proteins, plenty of produce, and whole grains for best overall, long-term health.

If you are going to try the keto diet, talk to your doctor first and don’t exceed the four-month period that the ADA recommends.