Diabetes in Control Nov 6, 2021
Author: Sheri R. Colberg, PhD, FACSM
Q: Can you speak to the ability or inability to “cure” T2D? Does it have to do with the loss of the pancreatic beta cells?
A: Yes, it has generally been shown that new-onset type 2 diabetes is easier to “reverse,” meaning that blood glucose levels can be so well managed that it appears diabetes has been cured. Over time, a loss of some insulin-making capacity occurs in people with long-standing T2D, particularly if it has not been well-managed, related both to the impairment of pancreatic β-cell function and the decrease in β-cell mass. (PMID: 27615139)
Q: Isn’t insulin resistance now found to be in T1DM as well?
A: Yes, anyone can develop insulin resistance, and it occurs in at least a third of people with type 1 diabetes as well, although it is not always associated with excess weight gain or overweight. Since people with T1D lack insulin due to the body’s own immune system killing off the pancreatic β-cells, greater resistance increases the total doses of insulin needed (whether injected, pumped, or inhaled). Thus, they have developed characteristics of both types and have “double diabetes.” (PMID: 34530819)
Q: Under lifestyle goals, would you include stress management?
A: Stress management was not assessed in the large multi-center clinical trials on type 2 diabetes prevention, but mental stress can certainly raise blood glucose levels due to the greater release of glucose-raising hormones like cortisol and adrenaline. It certainly would be beneficial to address better ways to manage mental stress as part of lifestyle goals for optimal blood glucose outcomes. (PMID: 29760788)
Q: As each person has their own limitations, how important is it to get a physician clearance and exercise guidelines before working with the client?
A: It really depends on the person’s circumstances. How intense will the planned activities be? Is the person currently sedentary? Has he/she been getting annual checkups to monitor blood glucose management and to check the status of any complications? Does he/she have diabetes-related or other health complications that could be worsened by physical activity? The lower the intensity, the more active an individual has been, and the lower the risk for cardiovascular complications, the less likely medical clearance is absolutely necessary.
The latest ACSM Consensus Statement on activity and T2D will be released in early 2022 in Medicine & Science in Sports & Exercise and states, “For most individuals planning to participate in a low- to moderate-intensity physical activity like brisk walking, no pre-exercise medical evaluation is needed unless symptoms of cardiovascular disease or microvascular complications are present. In adults who are currently sedentary, medical clearance is recommended prior to participation in moderate- to high-intensity physical activity.”
Q: Can flexibility training be used for warmups, or do you recommend it only after the workout?
A: While it is possible to do flexibility training at any point during a workout, joints tend to have a greater range of motion after blood flow to those areas has been increased with a light or short aerobic warmup. It may be prudent to do a quick aerobic warmup, some stretching, the full workout, and then more extensive stretching afterwards for optimal results.
Q: Was there any particular protocol for strength training? sets, reps, periodization? What is considered “intense” resistance work? Would fatigue based off of several sets of moderate intensity be recommended then?
A: That is a tough question, and it depends on who you ask. I have seen a lot of debate over the optimal strength training protocol during the many years I have been in the exercise/fitness world. If people are just starting out with resistance training, they will gain from doing even a minimal amount of training.
Starting out with 1-3 sets of 8 to 10 main exercises that work all of the large muscles groups at a light to moderate intensity is considered appropriate for most older or sedentary adults, many of whom have joint limitations or health issues. Moderate intensity is considered 50%-69% of 1-RM (1 repetition maximum) and vigorous is 70%-85% of 1-RM. Both intensity (fewer reps at a higher intensity) and the number of sets (3-5) or days of training (starting at 2, progressing to 3 nonconsecutive days) can increase over 2 to 3 months. Periodization is usually not undertaken by older adults, but may be appropriate for younger, fitter ones.
Q: Do you have any insight or are aware of any studies that involve high intensity (%1-RM) resistance training and T2DM? Or any studies that compare resistance training volume (Sets x Reps x Load)?
A: Some older studies have determined that glycemic management is improved by supervised high-intensity resistance training in people with type 2 diabetes (PMID 12351469). Others have also found that home-based (and, therefore, unsupervised) resistance training results in a lesser impact on blood glucose levels, likely due to reductions in adherence and exercise training volume and intensity (PMID 15616225).
Q: I’m still confused about glucose response to acute exercise. Which is better if you want to bring down your BG right now? Can you speak to the possibility of increased blood sugars with intense aerobic exercise?
A: Most light-to moderate-intensity aerobic exercise will lower blood glucose levels, assuming that some insulin is present in the body. (People who are very insulin deficient may have a rise in blood glucose from doing any activity.) Any activity that gets up into the intense/vigorous range, even if only during occasional intervals, has the potential to raise blood glucose due to a greater release of glucose-raising hormones during the activity. This is particularly true if the activity is short and intense. In individuals with any type of diabetes, declines in blood glucose during high-intensity interval exercise are smaller than those observed during aerobic exercise.
That said, if someone wants to lower blood glucose right now with exercise, it also depends on the timing of exercise. Doing something light to moderate for at least 10 to 30 minutes is the best bet, particularly after a meal when insulin levels are generally higher. Avoid doing intense aerobic or heavy resistance training as those may have the opposite effect. For early morning exercise, any intensity can potentially raise blood glucose due to higher levels of insulin resistance then and lower circulating levels of insulin in the body.
Q: I had an endocrinologist say that long runs or walks are better, and another one said to do a bit of weights.
A: Which activities someone chooses to do should depend on the goal of the training. Is it increased fitness, lowering blood glucose levels acutely, or gaining strength and improving overall blood glucose management? Long, slow aerobic training does have the benefit of increasing cardiorespiratory fitness and lowering blood glucose levels (in most cases). Resistance training, on the other hand, increases muscular strength and endurance and helps people gain and preserve muscle mass, which is where most carbohydrates are stored in the body. It may not, however, lower blood glucose levels, at least not acutely.
Both have their place in a weekly training regimen. Insulin resistance is lowered for 2 to 72 hours following a bout of aerobic training. Resistance training has more of a long-term impact on insulin action by enhancing carbohydrate storage capacity. The best advice is to do some aerobic training at least every other day and some resistance training at least 2, and preferably 3, nonconsecutive days per week. These activities can be done on the same days or different ones.