lashing carbs cuts medication use, improves or reverses type 2 diabetes, study says
January 9, 2009 | Shelley Wood
Durham, NC - A Duke researcher says that despite the lack of a "gold-standard" clinical trial proving the benefits of a low-carb approach, he has seen enough in his own patients to know that, at least for some, a very low-carb approach can essentially reverse diabetes, without adversely affecting lipid profiles. In his latest published research, Dr Eric C Westman (Duke University Medical Center, Durham, NC) and colleagues report that obese patients with type 2 diabetes randomized to a low-carbohydrate diet rather than a low-glycemic, reduced-calorie diet were more likely to experience improvements in glycemic control and, in some cases, patients were actually able to eliminate their diabetes medications and "reverse" their diabetes, at least as it is defined by hemoglobin A1c (HbA1c) level.
According to Westman, one of the novel aspects of this study was that patients in the low-carb group were maintained on what is typically considered the "induction phase" or "intensive" carbohydrate restriction of common low-carb diets. In the Atkins diet?and the Atkins Foundation funded this study?that induction phase means reducing carbs to <20 g per day for the first two weeks; in Westman et al's study, carbohydrate content was kept at <20 g for the entire six months of the study.
"Scientifically it's a no-brainer that the lower-carb diet affects the blood sugar better, because that's what physiology tells us," he told heartwire. "It's taught in Physiology 101 that what raises blood sugar is carbohydrates in the diet. There's no controversy about that. The question in the study is the degree to which changing the carbs in the diet affects type 2 diabetes."
Improvements in weight and glucose level
In all, investigators randomized 84 volunteers?mostly women?to either a ketogenic diet with <20 g of carbohydrates per day but no restriction on calories or to a calorie-reduced, low-glycemic-index diet (recommended calorie reduction of 500 kcal/day). Both groups attended regular clinic counseling sessions and were given nutritional supplements and recommendations for exercise: 30 minutes, at least three times per week.
At six months, more than 42% of patients had dropped out of the study, although both interventions had led to improvements in glycemic control as measured by HbA1c?the main outcome of the study. Strikingly, however, improvements in HbA1c, reductions in body weight, and improvements in HDL levels were significantly greater among participants randomized to the low-carb diet. Need for diabetes drugs, including insulin and/or oral drugs, was reduced or eliminated in more than 95% of people in the low-carb group as opposed to 62% in the low-glycemic-diet group, a statistically significant difference.
For lipid parameters, only HDL changes were significantly different between the two groups after adjustment for baseline differences, with improvements in HDL among the low-carb group being statistically greater?HDL levels were unchanged in the glycemic-index group. Both groups experienced significant improvements from baseline in VLDL and triglycerides.
To heartwire, Westman emphasized that there was a lot of variation in responses by lipid parameters to a diet that typically included more meat, cheese, and saturated fats. "I would say that we can allow a little increase in cholesterol if we're fixing diabetes," Westman said. "Diabetes is not a risk factor, it's a risk equivalent. I just don't understand the push-back, because we're not talking about raising or lowering LDL by 20 points, we're talking about fixing diabetes."
Mechanism of benefit
The authors point out that both weight loss and the reduced glycemic index contributed to the beneficial effects in the low-carb-diet group (since this diet also has a low glycemic index). But the higher impact of the low-carb diet in this study was likely driven by the lower carbohydrate intake, since the statistical significance of the different effect was maintained even after the researchers adjusted for weight loss.
"It is possible that the beneficial effect of 'low-glycemic' diets could be augmented by further reduction of the absolute amount of carbohydrate or by a reduction in caloric content," they write.
Asked to comment on the study for heartwire, Dr Robert Eckel (University of Colorado Health Sciences Center, Denver), who served on the nutrition committee of the AHA (which has long advocated fat restriction in the diet), pointed to information missing in the study, including details about the types of fat consumed and the reasons behind the high dropout rate.
Also commenting, diabetes researcher Dr Darren McGuire (UT Southwestern, Dallas, TX) called Westman et al's strategy "an intriguing concept."
"It's an interesting effect of HbA1c, but as we've all been so recently reminded, intervening on HbA1c is not the objective of diabetes management?the objective is to prevent micro- and macrovascular complications of the disease," McGuire told heartwire. "While some interventions that favorably affect HbA1c appear to reduce clinical risks, others do not and may cause harm. So, this diet intervention, fairly extreme in its nutritional composition and net metabolic effects above and beyond glucose metrics, just like any pharmaceutical intervention, requires evaluation over longer term and ideally in clinical-outcomes studies before one could endorse it on any scale. Most important, assessment of its clinical-outcomes effects, intermediate- and longer-term safety, and longer-term tolerability are all key questions remaining."
Westman agreed, telling heartwire that he has a $50-million study written up and ready to go at Duke Clinical Research Institute but doubts it will ever be funded due to the entrenched attitudes about fat and the politics around food and agriculture.
"We're in the gray zone where the ultimate study that needs to be done is a randomized clinical trial, which I'm all for," he said. But in the meantime, he plans to continue using a low-carb strategy in his practice. "Should I increase the fat in the diet, which science has shown to not raise cholesterol, even though a lot of people believe that to be true? Yes, if it means I can take people off medicine and improve their glycemic control," he insists.
But he also emphasizes that the low-carb approach is just one of several approaches to helping obese patients with diabetes, and it's not for everyone. "I have some college professors who were in the study who said, this is like I was eating in Italy. . . . I love it. So for some it's a cinch. But for the average person who gets into our studies, it's not a cinch, and it does require behavioral changes. What we learned from this study and others is that this is intensive, and in our clinic we won't let anyone go longer than a month without coming in, and if they have any sort of trouble with this, we prefer seeing people every two weeks. Some people we see once a week."
The key point, Westman continues, is that diabetes is "fixable." That notion has already been demonstrated in the bariatric-surgery literature, he points out. "This is a noninvasive approach, it's not quite as fast, not as drastic, and not as risky as surgery, but it still really reconfirms that with diet and weight change, diabetes is reversible."
It's also cheap for patients, he points out. "I would think that today, in this economic climate, that we would want nonpharmacological alternatives," Westman said. "I made one man happy today because I reduced his insulin in half in one day, and he was spending a couple hundred dollars per month on insulin. Patients like the doctor who does this."
Westman reports having no conflicts of interest.