Calorie restriction alone may not reduce cardiovascular events
Diabetes seems to be getting more and more unclear in terms of the appropriate path to treat and prevent the disease. The Accord trial, a large, randomized controlled trial, which I wrote about in my Jan. 25, 2011 article, showed that intensive lowering of glucose (sugars) with medications disappointingly showed no improvement in cardiovascular disease. Even worse, there was an increase in fatalities in the treatment group, compared to the placebo group (NEJM 2008;358:2560-2572).
So what about intensive lifestyle modification? We are constantly told that diet and exercise are very important for preventing and treating Type 2 diabetes. Many of us can relate to being told we need to lose 10 or 20 pounds. But the problem is that we are not given a road map as to how to best go about this process. Are all diets the same? How about exercise — does it matter how much and what we do? What does the evidence tell us?
We know that not all diets are equal and that diets fail patients all the time. In fact, there was a recent randomized clinical trial, the gold standard of studies, called the Look Ahead study, that looked at Type 2 diabetes patients and dietary effects. This trial involved intensive lifestyle modifications — dietary changes and increased fitness for one group were compared to a group given only diabetes support and education. The trial was halted because of its failure to impact cardiovascular disease.
We expect dietary trials to fail, but not one that is large, following 5,000 overweight or obese patients over 11 years, and funded by the National Institutes of Health. Part of the problem was that the amount of weight loss was less than 5 percent. The goal had been 7 percent, which should not be difficult to achieve when the patients’ mean starting weight was high. We know that the impact is greater with the more weight lost.
Worse still is that the interim analysis at year four of this study, published in 2010, showed encouraging results for reducing cardiovascular risk. There were significant improvements in parameters such as HbA1c (a three-month history of sugar levels), blood pressure, weight, HDL (“good cholesterol”), triglycerides, and number of medications. This is because patients had lost more weight at this point (Diabetes Care. 2010 Jun;33(6):1153-58; Arch Intern Med. 2010;170(17):1565-75).
At year one, analysis of the Look Ahead trial showed substantially more effect on reducing cardiovascular risk factors in Type 2 diabetes patients, with greater weight loss in the intensive treatment group. Those who lost 5 percent to 10 percent of their body weight saw results similar to the year four analysis above. And those who had a 10 to percent 15 percent loss of body weight experienced even greater risk reduction (Diabetes Care. 2011;34(7):1481-6).
However, there was good news with the trial: according to the authors, patients had lost weight and their physical conditioning had improved. The authors note that there was a low incidence of cardiovascular events (nonfatal heart attacks, nonfatal strokes, hospitalization from angina (chest pain), and death) for both groups, which made it difficult to observe a difference between the groups. Thus, this trial may have not been large enough to show an effective difference. I would argue that the weight difference may not have been great enough.
The treatment group with intensive lifestyle changes was following a calorie-restricted diet. This is not the same as a nutrient-rich, plant-based diet. Calorie restriction may help you lose modest amounts of weight, but trials have shown it does not necessarily add to longevity nor reduce risk factors for cardiovascular disease in Type 2 diabetes patients.
What is the message that this study is conveying? Does this mean that all diets are ineffective? Should we, to quote Marie Antoinette, “Let them eat cake”? I know some patients would like to be told that, but diet can play a significant role in Type 2 diabetes and its cardiovascular risk.
What is more important is diet composition. It appears to have more of an impact than just calorie restriction. In my Sept. 11, 2012 article, I go into much more detail on diet composition and an example of a nutrient-rich diet, with its beneficial impact on cardiovascular disease (Arch Intern Med. 2008;168:713-720).
In another recent trial, a meta-analysis (a group of 24 studies) with a dietary approach that involved a high-protein group compared to standard-protein group, the results disappointed (Am J Clin Nutr. online Oct 24, 2012). Though a high-protein diet showed a very modest reduction in weight, 1.8 extra pounds over three months, there was not a corresponding change in cardiovascular risk parameters, such as blood pressure, cholesterol and insulin levels. This analysis involved over 1,000 patients.
Again, it goes to the composition of the diet. In this case, the focus was on macronutrients, such as protein and carbohydrates, rather than micronutrients, including phytochemicals (plant nutrients).
Though we are encouraged to exercise for 150 minutes per week — or five days a week for 30 minutes each — this does not take into account what we do the other 23.5 hours on the days that we are exercising.
In a meta-analysis (a group of 18 trials), there was a greater than two-fold increased risk of developing Type 2 diabetes in those who were most sedentary, compared to those who were least sedentary (Diabetologia. 2012;55:2895-2905). If that is not enough, there was also a greater than two-times risk of having a cardiovascular event, such as a heart attack or stroke, in those most sedentary. It is a good idea to at least stand up, but also to walk around, for a few minutes every hour if possible during your waking hours.
Therefore, if there is one message I could hammer home, it would be that diet and movement do play significant roles in treating, preventing and reversing Type 2 diabetes and reducing its risk for complications. Weight and diet composition are very important to achieving these goals. Even very little exercise can have a substantial effect on diabetes risk reduction.
Dr. Dunaief is a speaker, author and local lifestyle-medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, go to the website www.medicalcompassmd.com or consult your personal physician.