Corresponding to research presented at the recent American Diabetes Association meeting in June, the NEJM published a study evaluating the cardiovascular benefits of diet and exercise in overweight diabetic patients. The results were surprisingly poor; there was no benefit.
Here are some details: 5,145 patients were randomized to two groups. One group undertook an aggressive diet and exercise program. The other group received diabetes support and education. Patients were followed for an average of 9.6 years with some patients followed as long as 13.5 years in the trial.
In the first year of the trial, the diet/exercise group had lost 8.6% of body weight vs 0.7% in the ‘education’ group. At the end of the study, the weight loss was more similar across the two groups: The diet/exercise group had lost 6.0% of their baseline weight (they regained some of the weight lost after year one) while the ‘education’ group was down 3.5% from baseline.
The study evaluated whether diet/exercise would show a benefit in terms of decreased risk of heart attack, stroke, hospitalization due to cardiac chest pain (angina), and death. The rate of these events (all combined) was 1.92% in the diet/exercise group vs 1.83% in the ‘education’ group – statistically not different. In other words, diet/exercise showed no benefit.
This begs the question “Why was there no benefit?” There could be several reasons:
- The first possibility is that other meds (statins for cholesterol control, blood pressure medication, and diabetes medicines) are collectively so good that it is hard to show a benefit on top of what these already produce.
- Another possibility is that by simply being in the study, the education group received unusually optimized care, thereby improving their health and making it also hard to show a benefit. This latter explanation is not satisfying, however, because both groups should have received this level of optimized care, and the benefits of diet and exercise would have been expected to manifest themselves on top of this.
- Yet another caveat is that this study only extended for 9.6 years on average. Perhaps exercise for a longer period would show a benefit. This is a fully reasonable hope, but it must be recognized that it is only a hope. There is no data to support this. Further, maintaining exercise for a lifetime (or at least longer than 10 years) requires tremendous commitment which might not ultimately be realized, even despite the best of intentions when beginning such behavior modification.
- Finally, this study was done in diabetic patients, and the conclusions might not apply to a non-diabetic population.
The observation that weight loss was greatest at year one (8.6%) and that patients subsequently gained back some weight highlights that diet/exercise is difficult to maintain.
With data in hand, it is worthwhile to consider whether docs should recommend diet and exercise at all. I personally have a strong belief in the value of these behaviors, especially exercise. Outside of the outcomes studied in this trial, other studies suggest exercise has long-term benefits on both bone health and cognition, potentially helping to prevent osteoporosis and dementia.
Personally, I will continue to recommend exercise should anyone ask my opinion, but I will do so with a slightly different mindset. I believe that fitness is important. Unfortunately, this data suggests that diet and exercise ultimately might not be powerful weapons in the fight to maintain good cardiovascular health.
source: Cardiovascular Effects of Intensive Lifestyle Intervention in Type 2 Diabetes (New England Journal of Medicine)