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Physical Activity Q & A with Dr. Sheri Colberg, Part 4

May 6, 2010

Sheri_ColbergBy Sheri Colberg, PhD


Q: Dr. Sheri, I’ve been doing a lot of research on Type 2 diabetes and exercise. I have had Type 2 for five years.  I am preparing for my first marathon. (I have raced halfs, 10K’s, 5K’s, etc….) My question relates to fasting insulin levels.  I was recently tested and the result was 3 uIU/mL (normal range is 3 -20). I’ve read in the past that a low fasting insulin level is normal in Type 2’s who are active. But I have also read that low fasting insulin levels are indicative of beta-cell impairment. Should I be concerned with this low level?  Is insulin therapy in my near future? T.


A: T, it’s impossible to tell at this point. If the low levels are the results of beta cell destruction and you stop exercising, then you would lose some of your insulin sensitivity and likely need more to keep your blood sugars in check. If the low levels are truly the result of your exercise training and enhanced insulin action, then your pancreas may still have the capacity to produce more if needed. It’s also possible that you have Type 1.5 (latent autoimmune diabetes of the adult), which accounts for more than 50% of the cases of Type 1 diabetes nowadays and ultimately results in some insulin needs, albeit over an extended period of time, due to long-term beta cell destruction. The new injectable medication, Byetta, may help with beta cell regeneration, and some people try that before resorting to basal insulin injections.

Q: Thank you. As a follow-up, let me say that there was some initial confusion five years ago when I was diagnosed with Type 2.  I was non-obese with ketoacidosis, BGs 400+. My PCP did have me meet with an endo and go over my blood work, and she apparently thought I was a Type 2. I wasn’t aware of the differences at the time but now I know there are anti-body markers indicating LADA. Should I test again for those? If so what am I looking for? I’m 43 and have been running for just over a year. I’ve never had a low while running, but occasionally do about 2 hours after if I haven’t refueled. I take metformin: 500 mg in the morning unless my fasting BG is less than 100, then I take 250; I take 1000 mg in the evening. I usually run before or after lunch. My current A1c is 6.4%, my height is 5′ 7", and my weight is 150 lbs. Right now I do about 20 miles running per week with a couple days of strength training, core, and a day of cross training. Regarding Byetta, I read in your book that it may help generate beta cells, but for athletes it seems to negatively affect exercise routines, especially for endurance athletes. Thank you for the book by the way, it’s great!

A: T, you can get tested for LADA, but I always say it’s not as important to know what type you have as it is to just make sure your treatment is keeping your blood sugars in check. You sound like a LADA to me (and I’ve seen a bunch of them who are athletes), so just don’t feel like you’ve failed if you need to eventually go on insulin to control your blood sugars. You may want to do some pre-/post-meal checking to see how high you go after eating as post-meal spikes can contribute to the development of complications even when your HbA1c is good. Byetta seems to do okay as long as you don’t take it before you exercise.

Q: Dr. Sheri, I have more follow-up questions for you. My typical post-prandial (2hr) are usually 100-140; that’s with 1000 mg of metformin, and usually less then 45 grams of carbs, and a decent amount of fiber. Should I be checking at the apex of BG 30 min post (or 30 minutes after commencing the meal)? Should I test without any meds and see what kind of readings I’m getting? I’m not so much worried about "failing" as I am about the impact that using insulin will have on my athletic activities. I know that there are a lot more Type 1 athletes out there than Type 2’s, even though there are a lot fewer Type 1’s. It seems much more difficult to manage activities using insulin; weight gain is more likely; and hypos are much more likely. I assume that it’s easier to get lower A1c’s, all things being equal, than it is on oral meds? My uncle’s mother-in-law is in her upper 70’s, has all types of health issues, doesn’t exercise, eats poorly, yet has better A1c’s than me! Thanks again for your responses. T.

A:  T, the typical post-meal BG peak is around 73 minutes after you start eating, but of course that depends on a lot of things, particularly the composition of the foods you eat. You can try an hour afterwards. For people with a normal, functioning pancreas, a post-meal BG almost never exceeds 140 mg/dl, even an hour after eating. If you start going up more, then some mealtime insulin would help. If you start going up overnight, some basal insulin would help.

Q: Dr. Sheri, here are the facts: I am a 53 year old male with an active lifestyle with a diabetic dad with neuropathy…. I have been a Type 2 diabetic for three years. I am 6′ tall, weigh 195 lbs, 102/70 BP and compete in mini-triathlons. I train for long distance aerobic events and exercise at least 5 times a week. My initial meds have gone from 2000 Met and 1½ glimepiride to 2000 Met and 4 glimepiride in three years and my A1c has gone from 6 back up to 7 recently. My eating habits have improved but my medication appears to be less effective. Is this unusual, or a symptom of something else?

My blood sugar readings can increase by over 50 from bedtime readings to morning readings. I can awaken at 3 am with tingling in my feet and note significantly higher glucose readings. Additionally, it is not unusual for my blood sugar readings to go up by at least 50 from the start of exercise to completion. The 2 hour 15 minute mark of moderate aerobic activity without any food intake is generally the peak of my blood sugar readings and then a slow decline … generally with a bout of muscle cramping which can be occasionally overcome. I use Hammer nutritional products when on a long event.

Do I need an endocrinologist? If so, how do I find one that has answers for athletic diabetics? I have your handbook and appreciate your effort in this relatively unknown area. My primary goal is to control my diabetes to keep the neuropathy away…. I would exercise whether or not I had it anyway! S.

A: S, in response to your first question, it is common if people retain their bad lifestyle habits, but uncommon in people who are as active as you. It is possible that you have been losing your pancreatic beta cells for whatever reason. Some types of diabetes cause gradual loss in adults (Type 1.5, or latent autoimmune diabetes of the adult), and you may have one of those instead of Type 2. If the pills stop working in any case, you would be advised to go on insulin to cover what your body is no longer able to make. Some people have also had some success with Byetta (which is injected). Exercise can cause BG levels to increase initially, especially when it is intense. If your sugars are going up overnight and your metformin is not preventing that, you may need to take a shot of basal insulin (like Lantus or Levemir) at night to cover your insulin needs. You probably could use an endocrinologist to help you figure out the best regimen for you. Keeping your diabetes in check will definitely help keep the neuropathy away, and the exercise you’re doing is great — keep it up!


If you have any physical activity, fitness, exercise, or nutrition questions for Dr. Sheri Colberg that you would like to see answered in my next column, please e-mail them to sheri@shericolberg.com.

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