Low Carb Diet for Type 2 Diabetes: The Evidence

Dr Jedha, Host

Hello there, thanks for joining me for episode 63 where we’re diving into the topic of low carb for diabetes, once a very controversial topic, which is now more widely known and accepted but still highly misunderstood by many. Specifically I wanted to take an opportunity to explore the evidence with you here. At DMP and over more than a decade, I’ve been encouraging a lower carb eating plan, because the science supporting it has been strong, and because when we consider the body’s biochemistry it just makes sense. 

02:02

The case is that most of us, whether we have diabetes or not, simply consume way too many carbohydrates. We don’t eat a balanced diet at all, as the primary macronutrient consumed is often carbs, and usually not quality carbs either, as we’re eating way too many processed foods containing refined carbohydrates and sugars. 

If you’ve been listening to the podcast for a while, you’ve heard me talk a lot about the importance of nutrition and that diet and nutrition are the most important part of your treatment. The most important part. More effective than medication, this is no secret, the research shows this time and time again. And I also know this to be true because I’ve seen this first hand, time and time again. Diet and nutrition are the most important part of your treatment. If you can get your diet and nutrition right, you can completely change your diabetes health. 

We have three primary macronutrients in our diet — carbs, protein and fat. As a person with type 2 diabetes or prediabetes, you’ve probably seen one of these macronutrients talked about the most, and that is carbohydrates. You’ve probably read that the amount and the type of carbohydrate you eat are important. It’s true, carbs are an important macronutrient for people with type 2 diabetes and prediabetes. That’s no secret. It’s a well-established fact that we’ve known for decades. 

Still, it took diabetes associations across the world a long time to acknowledge the benefits of low carb eating plans for diabetes. Even still, people remain hesitant and suggest we don’t have enough research on low carb diets, particularly long term research. The reality is, no diet has enough evidence, especially long term research—running trials over years isn’t possible in many cases because research is expensive and time consuming, among other things. But, in actual fact, low carb diets for diabetes probably have a larger amount of research than other diets, with more than 50 randomized controlled trials and we’ve also seen around 10 systematic reviews in the past 5 years or so, which is a lot. None have favored higher carbohydrate or low fat diets. 

04:40

Before we get down to some of the evidence, let’s just define what a low carbohydrate diet actually is. 

A low-carbohydrate diet typically consists of 10-26% of total daily energy intake from carbohydrates, equating to 50-129 grams per day in a 2000 calorie diet. 

It is different from a ketogenic diet. Many people talk about low carb and put keto under the same umbrella, but these are different. Here we’re predominantly exploring the evidence on low carb for diabetes.

05:23

Let’s start with a bit of history, because understanding the origins of low-carb diets for diabetes management helps us appreciate where we are today.

In the early 20th century, before modern diabetes medications existed, dietary management was the cornerstone of diabetes care. Cookbooks like the *1917 Diabetic Cookery* emphasized low-carb eating as the standard. Foods like bread, sugar, and starchy vegetables were explicitly listed as “forbidden.” Why? Because the connection between carbohydrate intake and blood sugar was clear, even back then. Without insulin therapy or modern medications, dietary control was the only tool available to manage blood sugar effectively.

Fast forward to the mid-20th century: as dietary guidelines shifted to favor low-fat, high-carb diets, the emphasis on reducing carbohydrates fell out of favor. These guidelines were based on limited evidence but heavily influenced public perception and healthcare recommendations. This shift coincided with a dramatic rise in processed food consumption, fueling the twin epidemics of obesity and type 2 diabetes. In fact, by the late 20th century, type 2 diabetes—once called “adult-onset diabetes”—was no longer confined to older adults. Rates of type 2 diabetes among children and adolescents began to rise.

The introduction of high-carb, low-fat dietary guidelines in the 1980s marked a pivotal—and problematic—shift.

Public health messaging during this era promoted carbohydrates as the primary source of energy, while vilifying dietary fat. This was largely based on flawed studies linking fat intake to heart disease. At the same time, the food industry began mass-producing low-fat, high-sugar products marketed as “healthy.” For people with diabetes, this advice was particularly damaging. Many were told to consume as much as 300 grams of carbohydrates per day—an amount that often led to poor blood sugar control, increased medication use, and worsening health outcomes.

Consider this: in the early 2010s, the American Diabetes Association recommended up to 75 grams of carbohydrates per meal for people with type 2 diabetes. That’s what a low-carb diet might recommend for an entire day of eating, not just one meal. The result of these recommendations? Many people with diabetes struggled to achieve healthy blood sugar levels despite following the “official” dietary advice.

This is around the time I really began investigating the evidence, as I was seeing clients struggling with blood sugar control and weight loss, and realized the guidelines were grossly inaccurate. Large diabetes organizations around the globe were worsening the state of diabetes, not making it better. 

Thankfully, the tide began to shift as more rigorous research emerged supporting low-carb diets.

By the late 2010s, studies began to challenge the status quo. A growing body of evidence showed that reducing carbohydrate intake led to improved blood sugar control, weight loss, and reduced medication use, compared to other diets and certainly the idea that low fat diets were superior had been set straight—with surmounting evidence showing they were certainly not superior. 

In 2018, the American Diabetes Association finally included low-carb diets as an option in their treatment guidelines for the first time. This acknowledgment was a significant milestone, reflecting the mounting evidence for the effectiveness of low-carb approaches.

Other organizations followed suit. In the UK, Canada, and Australia, diabetes associations released position statements recognizing the potential benefits of low-carb diets for managing type 2 diabetes. While these endorsements were often cautious, they marked an important shift in how diabetes care was approached globally.

Yet, despite these advancements, low-carb diets remain misunderstood and, in some cases, unfairly criticized, even to this day. 

One common argument is the supposed lack of long-term evidence. Critics often claim that low-carb diets are unsustainable or nutritionally inadequate. However, the reality is that no dietary approach has extensive long-term data due to the challenges of conducting such studies. Additionally, evidence supporting the safety and efficacy of low-carb diets is often stronger than that for other commonly recommended diets, such as high-carb, low fat or plant-based approaches.

For example, meta-analyses of randomized controlled trials—the gold standard of scientific evidence—has found that low-carb diets consistently outperformed other dietary approaches in reducing HbA1c, improving lipid profiles, and reducing medication use. These findings highlight not only the efficacy but also the practicality of low-carb diets as a sustainable treatment option for type 2 diabetes.

So, while the journey of low-carb diets has been anything but straightforward, the evidence supporting their use for diabetes management is undeniable. From early 20th-century cookbooks to modern clinical guidelines, the message is clear: reducing carbohydrates works. 

12:31

Let’s talk about the compelling evidence for low carbohydrate diets—not just from my own research, but from a wealth of studies showing their effectiveness in improving type 2 diabetes. 

As we just established, the scientific consensus around low-carb diets has been growing steadily. Randomized controlled trials (RCTs), the gold standard in clinical research, have consistently demonstrated the benefits of low-carb diets for people with type 2 diabetes. These studies show significant reductions in HbA1c levels, which is the most critical marker of blood sugar control, and these A1c reductions occur within just a few months of starting a low-carb eating plan.

I reviewed a lot of research during my PhD, and specifically the highest form of evidence are systematic reviews and meta-analysis because these take all the randomized controlled trials, bringing all the data together to compare them.

13:30

When we look at meta-analysis of low carb diets compared to other diets, people with type 2 diabetes experienced, on average, a 0.5% greater reduction in A1c at six months. That might not sound like much, but it’s highly significant, because again, what a meta-analysis does is take all the data from randomized controlled trials and draws that data all together to estimate the overall effect. It does this by comparing them to other diets, so by comparing low carbohydrate to moderate and high carb diets, so when they do this there is still an average 0.5% statistically significant difference in A1c levels. So in other words, low carbohydrate outperforms the other moderate and high carb diets—whatever form they may come in—low fat, Mediterranean, healthy eating, low glycaemic index, usual care, or high carbohydrate. An average across all the trials of 0.5% is an important improvement when we consider that even small decreases in A1c can lead to a lower risk of complications such as kidney disease, nerve damage, and cardiovascular issues, so if we expand that to a population level for instance, it would have a dramatic impact, a positive one.

At the heart of the evidence, we know the profound impact of low-carb diets has on blood sugar and insulin dynamics.

Carbohydrates have the most significant impact on blood sugar levels compared to protein and fat. By reducing carbohydrate intake, people with type 2 diabetes can stabilize blood sugar levels and reduce the insulin demand on their bodies. Reducing both blood sugar and insulin spikes is particularly beneficial for insulin resistance, a hallmark of type 2 diabetes, and this combo effect influences other functions throughout the body as well.

15:53

Low-carb diets have been shown to influence a wide array of health markers beyond blood sugar control. Research from my thesis and other studies highlights that low-carb diets lead to significant weight loss and reduced body mass index. Weight loss achieved through low-carb diets often comes with improvements in other metabolic markers, such as blood pressure and inflammation levels, creating a ripple effect of health benefits. 

A common concern about low-carb diets is their potential impact on heart health, particularly given the increased intake of dietary fats. However, research shows that these diets improve several cardiovascular risk factors. Triglycerides, a type of fat in the blood linked to heart disease, typically decrease significantly on a low-carb diet. HDL cholesterol, often called the “good” cholesterol, increases, improving the overall cholesterol profile.

17:32

One of the most important outcomes is a reduction in medication requirements when people with type 2 diabetes follow a low carb diet. This is incredibly important, and its an outcome that is consistently shown across 82% of studies—that’s a lot and this doesn’t occur in other diets. This tells us that the results for low carb diets in studies, for example, the A1c reductions, are likely more than what’s being reported, because of this reduced medication effect. Imagine if the medication were kept for example, then the A1c reductions would be more. Of course we can’t do that as it’s dangerous to keep taking medications when A1c is lowered, but just to highlight the point. The fact that medication is always reduced, also suggests that overall metabolic function and overall glucose metabolism is better in people with type 2 diabetes who follow a low carb diet, compared to other diets. Medication reduction from diet alone is such a critically important outcome. 

So, I went back to the evidence to see what emerged during 2024 in terms of the benefits of low carb for type 2 diabetes. Even in 2024 we’ve continued to see more and more research evolving:

More systematic reviews that continue to confirm everything we just discussed, that low carb diets lower A1c, reduce weight, improve lipids and reduce medication. 

19:28

When low carb diets are compared with low fat diets they’ve been shown to reduce key inflammatory markers in the body – CRP and IL-6. We know the systemic inflammation caused by high blood sugar and insulin resistance worsens diabetes health outcomes and contributes to complications like cardiovascular disease, so reducing these markers is a significant benefit for overall health.

19:56

We’ve all heard of very low calorie diets these days, using replacement shakes such as we talked about in episode 39 on the soups and shakes diet. Recent reviews that have compared the outcomes of eating a low carbohydrate unrestricted calorie diet with a highly restricted very low calorie diet have concluded that both are equally as effective for supporting people with type 2 diabetes to achieve remission. So which would you rather choose for the long term—option one, starvation and deprivation, or option two, an eating plan that allows for real, satisfying foods? It’s no surprise that option two is the preferred method because realistically most people cannot sustain a very low calorie diet. 

20:42

Reviews have continued to indicate that over the long term low carb diets improve cholesterol in comparison to other diets. Consistently these show that low carb diets lead to a greater increase in HDL cholesterol levels and a greater reduction in triglyceride levels. These are important outcomes because they are strong indicators of good cardiovascular health, reducing the risk of heart disease—a major concern for people with type 2 diabetes.

When it comes to other cholesterol outcomes, there is either no difference in LDL or total cholesterol or decreases in total cholesterol LDL levels. This is a reassuring finding for those concerned about low-carb eating plans, showing that the overall cardiovascular risk profile improves. For more on this, we spoke about understanding cholesterol in episodes 42 and 44.

Reviews have shown a low carb diet increases adiponectin levels, which is important because adiponectin is a hormone that plays a key role in improving insulin sensitivity, reducing inflammation, and promoting metabolic health. Higher levels are linked with better blood sugar control and lower risk of cardiovascular disease.

All and all, the benefits of low carb for diabetes continue. And of course, we can translate a lot of this evidence across to people with prediabetes, but there is also supportive evidence in people with prediabetes as well. 

23:28

There haven’t been as many direct studies of low carb in people with prediabetes, probably because diabetes occurs on a spectrum, with prediabetes coming before diabetes, so it’s assumed we can expect the same outcomes experienced by people with type 2 diabetes. And the studies we have do demonstrate the same significant outcomes as we see in type 2 diabetes trials. 

For example, one review comparing low fat to low carb in prediabetes found that both groups had an improvement in liver fat, total cholesterol, LDL and triglyceride levels. But it was only the low carb group that saw improvements in HDL cholesterol levels. In people with prediabetes, research shows improvements in blood glucose and insulin sensitivity and reductions in liver fat or fatty liver. Population studies have indicated that the rate of death in people with prediabetes is decreased with a low carbohydrate diet. Lower carbohydrate intake has also been demonstrated to achieve remission of prediabetes, or in other words, to reverse prediabetes. 

24:44

While carbs are an important nutrient of concern, diet quality Is critical. Certainly it’s not all about carbs. The quality of your nutrition plan is incredibly important, which is something we chat about quite a lot on this podcast. 

In terms of our health, and this goes for people with or without diabetes, it’s about choosing our carbohydrates wisely, favoring those that provide more bang for buck: more fiber, vitamins, and minerals; and with less impact on blood sugar, which is important for everyone but especially so for diabetes health because carbohydrates have the biggest impact on our blood sugar. 

While low-carb diets provide numerous health benefits, it’s essential to emphasize that not all low-carb diets are created equal. A low carb diet can still be an unhealthy diet if all you focus on is carbs, as there are many, many processed foods, candy and junk that are technically low in carbohydrates. Consuming nutrient-dense whole foods, with a good balance of proteins and fats, is crucial to achieving the positive outcomes associated with low-carb eating. We’ve covered various aspects of this in previous podcasts, and constructing a healthy low nutrition plan is what we help people do in our programs and memberships, so if you need help with that, please head down to our website to join us. 

For now though, I hope you’ve enjoyed delving into the evidence on low carb with me today. A healthy low carb nutrition plan is a very powerful way to eat to rebalance metabolism and keep our metabolism running efficiently. A healthy low carb nutrition plan, such as our T2Diet, helps to keep blood sugar levels balanced, lose weight efficiently and maintain a healthy weight, balance cholesterol, reduce inflammation and more—and it’s all backed by science and over a decade of experience too. 

Well, that’s all from me today. Take care until next week. 

Dr Jedha, over and out.