I don't know a lot about how exercise works, since I last did serious exercise when I was in the rowing squad in high school and that was a while back. I've only taken a serious interest again in the quest to manage my type 2 diabetes, and that quest has certainly raised my level of interest and curiosity, especially in relation to not only diabetes but for older people in general.
My wife has taught me quite a bit because she was a serious speed skater in Japan, and in fact won a sports scholarship to university as a speed skater. She knows an amazing amount about how the body works and exercise, which I hadn't realised until I started to research things myself.
What caught my eye were a number of studies which seem to say that moderate exercise, in various forms, could be interpreted as being "better for you" than more strenuous exercise. And here I am paying attention to diabetics needs in particular.
For example, if was reported from Britain that obese boys versus lean/healthy boys reached their maximum fat burn rate (known as Fat Max and is the VO2 peak) at low intensity exercise, while in contrast the lean-fit boys had to move into high intensity exercise to burn the same fat. Or in other words during high intensity exercise the lean-fit boys burned off much more fact than the obese boys doing high intensity exercise. In fact the study found that during high intensity exercise the obese boys fat burn rate fell sharply, even before they reach intense exercise levels.
The researchers suggested that obesity is related to a sedentary lifestyle which in turn reduces muscle capacity and its ability to utilise fat as energy. And I found it interesting that:
...obesity changes muscle type. Obese people have higher levels of type 2 “fast twitch” muscle fibres, which burn off more carbohydrate. Lean people have a higher proportion of type 1 muscle fibres, which burn off more fat, ...
While that was in my mind I chanced upon another study in relation to telomere length which found that women aged 50-70 who had engaged in moderate exercise consistently for a "lifetime" "exhibited "significantly longer telomere lengths" than both the lowest exercising and the most intense exercising group.
The study found no difference between the second highest exercise intensity group and the moderate group (which was the third highest or second lowest - there were four categories). I think this means that while the moderate and "moderate+" groups showed no difference that the moderate+ group statistically did not have such a significant difference with the lowest and the highest exercise group, which I speculate could be to do with wider variability for example in the moderate+ group.
The conclusion was that moderate lifetime physical activity levels "may provide" a protective effect on peripheral blood mononuclear cell telomere length as compared to both low and intense exercises. The level of moderate exercise so defined was Exercise Energy Expenditure (EEE) of 991-2340 kcal/wk.
Oddly enough, elsewhere, the same study is reported as part of an MA thesis which has just three groups and reports that the moderate group had longer telomere length than the lower or higher groups. It used a moderate EEE of 1001-3500 kcal/wk.
This may be important for diabetics because telomeres are part of the built-in clock that exists in all genes. Eventually, the clock winds down, which is part of the aging process that ultimately leads to death. In diabetics this "wind down" is accelerated and thus consistent moderate exercise may be a way to slow it down. In addition, shortened telomere length and decreased telomerase activity have recently been associated with perceived psychological stress and cardiovascular disease risk factors and onset of dementia.
From Glasgow, the Institute of Diet, Exercise and Lifestyle, reports a "consistent picture indicating that regular physical activity substantially reduces the risk of Type 2 diabetes". Even more so for those who are inactive or in the high risk BMI scales.
The data indicate that protection from diabetes can be conferred by a range of activities of moderate or vigorous intensity, and that regular light-intensity activity may also be sufficient, although the data for this are less consistent.
How much exercise is necessary? This study basically says more exercise for those people at higher risk, and even of vigorous intensity. The baseline is that "increasing moderate physical activity by approximately 150 minutes per week reduces risk of progression to diabetes, with this effect being greater if accompanied by weight loss".
A key message of this study is that while 150 minutes per week of moderate activity confers benefits, higher levels of activity may be necessary to maximize diabetes risk reduction for those people with higher risk of the disease e.g. people with a high body mass index and a family history of diabetes. In contrast at low risk will remain at low risk of developing diabetes whether they are active or not.
It seems amazing that historically, diabetics were not encouraged to exercise. As recently as 2005, the American Diabetes Association was saying "no" to weight training for diabetics – especially older patients – for fear of complications such as stroke or heart attack. I guess they need to be conservative and look for more evidence of risk versus benefits.
Today diabetics are encouraged to exercise, and aiming for physical activity of ~2.5 hours per week and weight loss of as little as 5% to 7% of body weight are the core objectives.
My interpretation of the studies above is that if I was newly diagnosed and not doing regular exercise and also overweight, that moderate exercise to initially burn off fat would be the way to go, building up later in more intensive exercise to build muscles. And focus on reducing the waistline, that's important.
The main message is don't go exercise crazy, and bear in mind that in fact doing too intense exercise to start may not only be more risky but may not be doing you as much good on a day-to-day basis as moderate exercise. Moderate exercise will also potentially moderate the aging process and some of the complications that associate with normal aging more so than intense exercise, according to my interpretation of the various study findings so far.
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