Recent Research on Low (and Low-ish) Carb Diets for Type 2 Diabetes

Carb reduction as a strategy for managing Type 2 Diabetes is gaining an increasing amount of mainstream attention recently. A few years ago, even the journal of the American Diabetes Association published a meta-analysis suggesting that low-carbohydrate diets may have some benefits.

So what’s behind the changing recommendations? Partly, it’s research that’s already been done and just needed to be brought to everyone’s attention. But there are some interesting new studies from the past year or so – here’s a look at what’s been going on since 2014 or so.

This is not a comprehensive list of all studies published on carbs and diabetes; it’s not even a comprehensive list of all those studies from the past few years. It’s just a closer look at some that you might find interesting.

Benefits of Low-Carb Diets

The good news is pretty simple on the surface: several recent studies have found that a low-carb intervention is better than a low-fat intervention for all different aspects of Type 2 Diabetes.

Blood Sugar and Lipids

The low-carb benefit everyone thinks of first is blood sugar control, often measured by HbA1c (basically a measurement of how good your blood sugar control is in the long term). It was pretty clear from almost all the studies that lower-carb was better for blood-sugar control, and also for blood lipids (cholesterol and triglycerides).

To start off with, this study (also in the American Diabetes Association’s journal) found that a low-carb diet was better than a high-carb diet for reducing HbA1c and triglycerides, for getting the participants off medication, and for increasing HDL cholesterol.

In another study, a low-carbohydrate diet improved HbA1c (and incidentally also blood lipid levels) more than a calorie-restricted diet – namely, the low-carbohydrate diet improved them significantly while the calorie restriction didn’t improve anything.

In the first study, the low-carb diet was 14% carbohydrate, and the subjects basically complied with it. On a 2,000 calorie diet, that would be about 70 grams of carbohydrate. The carb target in the second study above was between 70-130 grams/day, and at 6 months, the low-carb group was basically compliant, eating an average of 125 grams of carbs/day. This is the low-end of moderate by Paleo standards – it’s nowhere near extreme. If you ate one large sweet potato, a couple parsnips, and a big pile of non-starchy vegetables, you’d hit around that level.

But does low-carb have to be that low to see benefits for blood sugar? Are there benefits to going lower? Are there benefits to going higher? A few other studies looked at exactly that question.

• This one found that a very low-carb diet (designed to induce ketosis) had better results than a moderate-carb diet.
• This study took a slightly different approach: how little restriction can you get away with and still see the benefits? The researchers found that patients with higher HbA1c (poorer blood sugar control to begin with) benefited from more intensive carb restriction, while patients with better blood sugar control could get away with a little bit more carbs.

This is a pretty interesting line of research: if a less-restrictive diet can achieve the same results as a more-restrictive diet, why wouldn’t you pick the less-restrictive one?

Other Benefits

Some other recent research has looked into benefits beyond blood sugar control – particularly two studies out of Sweden. In this study, researchers wanted to test whether a low-carb diet would help with inflammation. Patients were advised to follow either a low-fat (30% fat) diet or a low-carb (20% carb) diet with equal calories. No food was provided, but they did give the participants recipes. The low-fat participants hit their target (an average of 29% energy from fat) and the low-carbers came close (average 25% from carbs)

The low-fat dieters lost an average of 4 kilograms (8.8 pounds), and the low-carb diet lost around 4.3 (9.5). The difference in weight loss wasn’t statistically significant, as you’d expect from diets where calories were held constant. But only the low-carbers improved their markers of inflammation. (Unlike the low-fat group, the low-carb group also showed positive changes in HbA1c and HDL cholesterol, and significantly reduced the amount of insulin they had to take).

Another study from some of the same researchers tested the long-term effect of a low-fat diet compared to a low-carb diet on health-related quality of life (things like chronic pain, health-related restrictions on daily activities, etc). Again, the low-carb diet was 20% carbs, with both diets restricted to the same number of calories. They found that both groups lost roughly the same amount of weight, but only the low-carb group improved their health-related quality of life.

This study has some gems about practical implementation of a low-carb diet:

• “The low-carbohydrate group described that they felt less hungry and were less prone to sweets.” – suggesting that in people who aren’t study subjects, the calorie restriction would actually be doable in the long term. That’s the real benefit of low-carb diets.
• “Both diet-groups mentioned that it was supportive if the whole family could follow the same diet.” – social support: you need it!

Moving from Sweden to Japan, and from quality of life to fat loss, this study found that in Japanese men, even a very modest carb reduction (from 50% to around 40% of energy) reduced dangerous visceral fat in proportion to the amount of carb restriction.

Other Interesting Articles

Not all the interesting articles published in scientific journals are intervention studies where researchers do experiments on their subjects. There’s all kinds of other stuff there: evidence reviews, meta-analyses, position statements…here’s some of it:

• This article is fascinating, because it actually looks at the switch from traditional starches (like tubers) to refined grains on a global scale as the root cause of rising diabetes rates in developing countries. We tend to think of diabetes as a problem of the first world, but it’s a very global issue, and with a history of food scarcity, people in developing countries may be even more at risk.
• This review of the evidence is really more of a science-heavy low-carb manifesto; the authors are obviously very irritated by the failure of low-fat guidelines to control rising rates of diabetes and urgent about finding a better solution. The authors give 12 points in favor of carb restriction for diabetes (both Type 1 and Type 2), and address issues like saturated fat, cholesterol, and safety as well as efficacy. If you need any evidence to quickly email a friend, this is a good choice. It’s a free full-text and very readable: check it out if you’re at all interested in the science of low-carb diets.

Summing it Up

None of these studies are particularly groundbreaking, but they’re just adding to the growing body of research that a moderate to low-carb diet may be effective for managing Type 2 Diabetes. Remember that most of the low-carb diets weren’t extreme – most of them still allowed for at least one serving of starchy vegetables per day, and they still showed benefits. At 20% of energy from carbohydrates, you could have a potato (yes, white potatoes are OK) or a sweet potato every day and still have room for lots of other non-starchy vegetables, nuts, avocado, and other foods.

Hopefully with the recent increase in interest, we’ll start getting more answers to the questions like “how low is best?” – not to mention more advice on carbs for Type 1 Diabetes, which often gets lost in the shuffle.