As I’ve brought up before, it’s important not to over-interpret preliminary evidence or attempt to extrapolate from basic science to clinical reality. So while I’ve long suspected that strength training would have a benefit when it comes to diabetes development, I’ve avoided actually saying that.
And so it’s always nice when the clinical studies back up what I suspected. Hooray!
One of the things I learned from my exercise physiology education was that strength training upregulates GLUT4 on muscle cells. GLUT4 is an insulin triggered transporter for glucose. This means that strength training increases the ability and sensitivity of the of the muscle cell to take glucose out of the bloodstream and put it in the muscle cell.
Theoretically, this should reduce the likelihood of diabetes. But does it?
To the research!
I recently came across this study from JAMA: A Prospective Study of Weight Training and Risk of Type 2 Diabetes Mellitus in Men. The large Health Professionals Follow-up Study was used to track physical activity in 32,002 men for 18 years. Any physical activity reduced the risk of developing or dying from diabetes. Strength training was more effective than cardiovascular training. Both was better than just one.
Things to note about why this research is notable for this conversation:
- The size of the study. Tens of thousands of subjects followed for nearly 2 decades is a lot.
- The effect sizes are large. For relative risk, reducing the number of cases by up to 1/3, of one of the most common and expensive lifestyle modifiable diseases, is a big deal.
- P value was tiny. P < .001. This wasn’t one of those, “if I hack it I can get P to equal .05” types of studies.
- Dose response. There is a clear, fairly linear, dose response of more weight training leads to lower risk.
- Normal living humans. Study was conducted on humans. The people were not having their lives dictated to them by researchers.
The best results were seen at 150+ minutes per week of weight training, cardiovascular exercise and for both. This may seem like a lot, but it’s hitting the gym 3 times a week and going for a 30 minute brisk walk most days.
There are limitations to the study, of course. It’s not randomized, but the best studies of this type of question can’t be because it’s hard to control behavior for that long in free-living humans. It’s only in men. Weight training is not necessarily defined the same as strength training.
As I’ll keep saying, the best outcomes result from a complete approach to physical activity which includes strength training, cardiovascular exercise, flexibility/range-of-motion and neuromotor (balance/agility) training.