Does Diet and Exercise Prevent Diabetes or Help Persons with Diabetes Live Longer?

It's such a no-brainer, right?  If persons at risk for diabetes would only eat right and exercise more, they'd avoid the disease.  And for those who develop diabetes, diet and exercise will reduce death rates and complications.

Yes and no, say Elizabeth Sumamo Schellenberg and colleagues at the University of Alberta.  Their review of the mixed published scientific evidence on the topic appears in the October 15 issue of the Annals of Internal Medicine.  The purpose of their study was to ascertain the impact of diet and exercise on the prevention of "Type 2 diabetes," as well as lowering complications among persons with who had established Type 2 diabetes. 

To be included, studies had to be prospective and compare the outcomes from an intervention versus a randomly selected control group. The study could only be included if it examined the impact of exercise plus diet and "one other component," such as "counseling, smoking cessation and behavior modification."  The outcomes had to include the development of Type 2 diabetes (in the prevention trials) or complications (in the treatment trials).

1289 candidate studies were found but only 20 made the grade. Nine were prevention trials and 11 were treatment trials.

For the prevention trials:

The interventions lasted from 6 to 72 months, with follow-up going for 3 to 20 years for between 39 to 3234 participants.  The counseling varied and included group and/or individual with or without tobacco cessation, telephony, goal setting, cooking classes or pills involving a range of physician and non-physician professionals.

Results?

Seven of the nine studies showed that diabetes can be delayed. When the results were pooled, compared to the control patients, the risk of developing diabetes over 10 years was only a third and the difference was statistically significant.

But, there was no detectable impact on cardiovascular disease events or on eye, kidney or nerve damage. That may have been due to not all the studies including these outcomes as well as the time it takes for these complications to occur once diabetes develops.  With more patients or more time, a difference could have become apparent.
 
For the treatment trials:

The interventions lasted from 6 to 48 months with follow-up for 6 to 93 months. The counseling was as varied as the prevention trials but included glucose and blood pressure monitoring as well as stress management and, in one instance, a three day residential retreat. There was likewise the range of professionals who provided the interventions.

Results? 

Compared to the control patients, there was no statistically significant difference in all-cause mortality.  Some individual studies had beneficial outcomes involving cardiovascular events or diabetes complications, but they included the aggressive use of medications.  There were no sustained impacts on weight or dietary intake.  And if pills were not included, there was also no real improvement in measures of blood glucose control.

The Disease Management Care Blog's take?

The good news is that there is good evidence that exercise and diet can prevent diabetes.  The bad news is that it takes years for that "return on investment" to declare itself and typically involves interventions that fall outside the traditional health care delivery system.  It's unlikely, thinks the DMCB, that current iterations of payment reform (value based purchasing, bundled payments or upside risk) can be marshaled to make this a reality.  That being said, population health management (PHM) companies like Omada Health are making their evidence-based services available to, for example, employers who have a longer term commitment to the well being of their "human capital" outside of the traditional insurance market.

The bad news is that once diabetes declares itself, diet and exercise don't result in life extension, and control of complications as well as overall blood sugar levels is more a function of pills than lifestyle. Accordingly, expectations need to be realisitically shared with patients and PHM should emphasize taking the pills as prescribed.

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