April 23, 2008

Study Shows Benefits of Exercise on Diabetes are Minimal

An article cited in the medical news recently states "...the prescription of group-based brisk walking represents an equally effective interventional strategy to modulate glycaemic control and cardiovascular risk profile in type 2 diabetes patients compared with a more individualised medical fitness programme."

Sounds good, eh?

But let's look at what they really found.

The study is here: Brisk walking compared with an individualised medical fitness programme for patients with type 2 diabetes: a randomised controlled trial. S. F. E. Praet et. al. Diabetologia, 10.1007/s00125-008-0950-y.

The researchers took 100 people with diabetes and put half of them on a brisk walking regimen that included some resistance exercises. They put the other half on a traditional gym regimen that used machines like elliptical trainers and emphasized weight lifting.

At the end of the year they measured the improvement of the 37 people who stuck with the program.

Thirty seven? Out of one hundred. Hmmm. That's only a tad more than 1/3. In fact, several people recruited dropped out at the very start of the study so only 92 began the exercise programs. So far, this study sounds a lot like real life to me.

But since some did stick with it, let's look at how effective these exercise programs were for blood sugar control.

For all participants, the mean A1c dropped by .14%. That translates out to a lowering of average blood sugar of 4 mg/dl--which is underwhelming when you learn that the beginning average A1c was 7.13% ± 1.36.

The group that did brisk walking dropped their average A1c by .11 and the traditional gym program folks by .18. Hmmm again. That equates to something like 3 mg/dl or 5 mg/dl. It is starting to look like they could have achieved a much better lowering of A1c by dropping 15 grams of carbs from their daily intake.

Their fasting blood sugar declined about 4 mg/dl--in a group that started with a fasting blood sugar that averaged 152 mg/dl.

But surely there must have been other benefits? What about weight? Gyms sell their programs as being a major route to weight loss. Well, that wasn't much better. The people doing the brisk walking lost on average .2% of their BMI. (The researchers did not give the actual amount of weight lost.)

At my BMI, .2% computes to a loss of 1 lb. Over an entire year. The gym group did only slightly better. They lost an average of .8% of their BMI. That is about 4 lbs.

The rest of the parameters they measured weren't much better. Systolic blood pressure decreased about 10 mmhg. Diastolic (the bottom number) by about 5 mmhg. Cholesterol decreased by a similar trivial amount.

I'm scratching my head. Did the researchers really call this an "effective interventional strategy to modulate glycaemic control and cardiovascular risk profile in type 2 diabetes patients?"

Would any sane person put themselves through all the effort of doing all that exercise if they knew in advance that their results would be so unimpressive?

I like walking. It does good things for my leg muscles and makes me feel healthier, but having read this study I feel a lot better about my own results which, over the years, have been no weight loss, and no change in blood pressure or blood sugar no matter how long or regularly I walked.

I thought I was some kind of oddball, but these results suggest I am in fact typical.

But you do have to wonder who comes up with these definitions of "effective!"


Anna said...

Between my own experiences over the years trying to lose weight by going to the gym (gained some muscle and became more fit, but never lost weight) or NOT going to the gym but eating LC ( I easily lost fat weight and maintained muscle), this doesn't surprise me. What I suspected was confirmed for me when I read Gary Taubes book this year.

I'm like you, I like to walk and have been doing it regularly with a neighbor friend. But I have no illusions that it will fix my glucose problem or perform weight miracles. Letting go of starchy foods was and is my best strategy for BG control and weight. Exercise just adds to those benefits.

Anonymous said...

Was the analysis of this study done on the standard "intent to treat" basis, or did they actually confirm that the participants followed the exercise programs? What were the actual exercise programs?

My own experience has been that losing 100 pounds and dramatically lowering my A1C over the course of a year and half wasn't too hard after I combined a serious exercise program with paying attention to my diet. Diet alone didn't seem to do the trick.

Rachel... said...

Exercise makes all the difference for me, whether I'm doing lower carb or not. It's the only variable that helps me not spike 100 pts after meals with >15 g carb intake. (I feel too sluggish to exercise if I consume less than that. I'd rather exercise to combat stress and depression than feel rotten on extreme low carb.)

Low Carb Band-It said...

Question? I'm walking to improve my insulin sensitivity. I'm not diabetic (fasting runs about 101 and my A1C's are about 5). But I have the toughest time losing weight (even with extreme low-carbing - under 5 net carbs a day). I'm on 5 glucophage a day, every herbal suppliment for insulin senstitivy and my fasting insulin levels are extremely high (around 70-80). I have PCOS and the ONLY hope for me to lose better is to get my insulin sensitivity more normalized. I've read that walking can help with that. I wonder if this is true?

Jenny said...

Low Carb Band-it,

Dr. Bernstein writes that he has found that for some people with PCOS losing weight is well nigh impossible, even with his diet and every drug he knows about.

I'm at the point myself where losing weight is ridiculously hard, even without much insulin resistance. I think the speed of your metabolism has a lot to do with weight loss, beyond blood sugar issues.

And research shows some of us have defective mitochondria, the fat burning parts of the cell, so we don't burn fat properly no matter what exercise we do.

I have seen studies that show that exercise is very helpful for some people and completely useless for others depending on mitochondrial issues.

Wish I had some wonderful solution for resistance to weight gain, but I don't. I've been working for several months to get 3 lbs off and not getting very far and my insulin is low as is my insulin resistance. My age is high, though, and that means my metabolism is slow-w-w.

Anna said...

The more I look into exercise, the more I realize that walking really isn't the *best* exercise for improving glucose regulation, though I do enjoy a half hour, 2 mile walk on a hilly loop with my neighbor friend a few times a week. But that walking is as much for a bit of fresh air and sunshine, socializing, and garden gazing, as it is fir exercise. I think I need to do more that is directly working my muscles with resistance and strength building. My weight is more or less fine and currently is easier for me to manage with diet (high fat, moderate protein, grain-free LC).

I understand that walking is the easiest exercise to recommend, as it is free, relatively fast and easy to do (obviously that varies, depending on the walker). But walking also probably isn't the most effective use of time or effort compared to some other forms of exercise. I think strength building may be a better, more efficient sort of exercise and when done at home, it can take a *lot* less time than walking with better results.

Typical "cardio" exercises don't really increase lung or heart capacity (though people, even docs, think they do), they just indirectly make the muscles a bit stronger, therefore the lungs and heart don't have to ramp up their rate so much to supply more oxygen. You still won't win the Tour de France if Lance Armstrong's lungs and heart are transplanted into you.

Building muscle strength directly is a better way to improve insulin sensitivity in muscles, increase the number of mitochondria in muscle tissue, and raise the metabolic rate.

I'm currently looking into the Slow Strength (aka Slow Burn) way of weight training. I have the Slow Burn book by Fred Hahn & the Drs. Eades and have started their home routine, but I've noticed that a couple of gyms near me are now advertising their version of slow strength. I might try that, too.

I've never really been one who likes to exercise for the sake of exercise, unless I had a buddy who was also keen to join me. These days, it's harder to coordinate schedules with a buddy, so I need to accept that I will exercise on my own (maybe I can get my husband to join me if he sees that it isn't a lot of time and drudgery, like stair stepping or treadmilling).

The other thing about strength that has really been hitting home with me is how it impacts old age. Balance (and reduction in fall-related injuries), resistance to illness and the effects of illness, as overall health are greatly improved with the muscles stay strong. Keeping the muscles strong requires adequate protein intake and flexing those muscles as long as possible, either through intense use or exercise. It doesn't require muscles like Arnold Schwarzenegger's. :-)

ItsTheWooo said...

I find that walking for about an hour or so per day lets me tolerate slightly more carbohydrate (note that I do not measure my blood sugar with meters as I am not diabetic). When I say I can tolerate more carbohydrate, I mean that I do not get the mood and energy problems that I associate with it. With exercise I can tolerate maybe 70 carbs, and feel the same as I would if I ate 50 carbs without exercise. Calorie restriction and protein restriction also helps me tolerate more carbs and work similarly to exercise. Calorie restriction is probably the most effective of all three methods, and if I restrict my calories enough I can eat quite a lot of carbs without feeling any telltale signs. Calorie restriction is probably the only reason that low fat diets are at all effective, it's hard to spike your blood sugar when you're semi starved. OF course, the side effects of calorie restriction make it intolerable long term (like hunger and a different sort of lethargy/mood problems).

Even though I do notice a positive effect from activity, I will never deceive myself into thinking it is a major component of weight or blood sugar control for me. It's almost entirely about carbs, with calories being second, and exercise being a very very distant third.