Minimizing fasting glucose with exercise

So, my fasting blood sugar numbers have been consistently between 93 and 95 mg/DL – and while I’m not convinced that this number really should even be classified as gestational diabetes, it does technically meet the really aggressive new definitions that have been adopted for gestational diabetes in recent years (which flags about 20% of women in the US). And on days when I am up all night long with Samson, my blood sugar can between 100 and 110mg/DL when i Wake up :frowning:

What’s frustrating is that my post-prandial numbers are totally normal – always below 120 at 1 hour and often below 100 or 90, and by 3 or 4 hours by blood sugar is often in the 60s or 70s. So I really don’t think taking a long-acting insulin or metformin makes sense, given that I’m already running on the low end. I’m honestly scared of going hypoglycemic at night.

Anyways, @Eric, or anyone else who has knows a lot about how exercise affects blood sugar, I’m wondering what is the optimal time to do exercise in the day so that my body is ferrying glycogen into my muscles overnight, thereby reducing my fasting blood sugar?

And what would be a good exercise regime to increase insulin sensitivity overnight? Is cardio like running enough? Or should I be doing some kind of strength training?Because I’m somewhat pressed for time, my plan right now is to just run up to the top of the hill on our street – so three or four long blocks of pretty steep ascent, followed by run back down. I can’t take an hour for exercise during the day because of work. So I’m hoping to accomplish this goal with 30 minutes sometime during the day.

I am not concerned about my BGs in the immediate aftermath of the exercise as I’m not struggling with numbers throughout the day. I just want to keep the fasting numbers in range.

I’m happy to try dietary tips too – and online there are many, like having a small protein or carb snack before bed – but so far the effect seems pretty limited. It seems like you can do a ton of stuff to fix post-prandial numbers with exercise but fixing fasting numbers is a lot tougher.

And then there are all these hacks that seem pointless. A lot of women suggest things like “test at 10 hours instead of 8 and your number will be golden” – but that seems silly given that it is not actually changing your overnight fasting numbers, which are presumably the problem rather than the specific, individual number 8 hours after you last ate.

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There are a lot of interesting things to look at!

Cardio is what you want. Weight lifting has benefits for other things, but if you want to specifically target BG, it would definitely be cardio.

Your body will use multiple fuel sources at the same time, and use them in different amounts for whatever conditions make sense at the time.

Since you are looking at something specifically for fasting times, and for longer times at night, you want to do something with an intensity that makes the most use of muscle glycogen, rather than fat metabolism or glucose that is in your blood at the time of the exercise. Ideally you would do something that causes your body to pull glucose from your blood during the nighttime in order to replace muscle glycogen.

Any exercise will help you to some degree, but if you burn a higher amount of fat, it will not accomplish this as effectively. If you do something that is too low of an intensity, your body will use more fat. You don’t want that.

If you do it right after you eat, your body will also use more of the immediately available glucose, and that reduces the amount of muscle glycogen you will use.

Ideally, you want something before dinner, and long enough after lunch so that your body’s choice of ideal fuel is muscle glycogen.

You want your intensity to be more muscle glycogen related (as reference, see how-does-my-body-fuel-exercise ).

Since you have time constraints, you want to try to do a steady state cardio event that lasts the duration that fits into your schedule.

So if you only have 30 minutes and you wanted to run, that time should be a fairly consistent effort. Aim for steady state heart rate for the whole time. The intensity or pace should make you feel this way:

  • “I could to this for 10 or 15 minutes with no problem!”
  • “30 minutes? Well, I can do that with some effort. It won’t be too hard, but not exactly easy either…”
  • “60 minutes? There is no way I could do this for an hour. I am glad it is only 30 minutes…”

Keeping a steady state heart rate with hills is tough, because you have to run down the hill so much faster to keep the same heart rate that you had running up! If your heart rate spikes and drops too much, you will increase the release of liver glycogen to fuel the run, which won’t be as effective for the long nighttime lowering of BG that you are looking for.

Another alternative would be a stationary bike or treadmill. Are you in the Bay Area? There are some nice flats in Golden Gate Park. Also along the Embarcadero and Fisherman’s Wharf are flat. And my favorite place to run in San Francisco is across Golden Gate bridge which is also relatively flat.

Long winded answer, so my quick summary:
steady state run, moderate intensity, before dinner

Another side note. That cracked me up! I mean, that’s like me saying, “If I never test my BG, I am never low or high!”


Bear in mind that safe exercise levels are probably less for a pregnant lady than for other cases… maybe just brisk walking, pool aerobics, or something would be best option. I’d discuss with her OB what safe and prudent exercise levels would be like for her. I know shellys doc didn’t want her pushing her heart rate over 140 while pregnant… running of any fashion definitely does that for me…

That said, I am still really surprised if her doctors are expressing any concern whatsoever based on the blood sugar readings she’s reported here… they sound perfect to me. But exercise is good nonetheless

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Thanks @Eric this is really useful information! My intuition was that I should try running around 5pm or 6pm just before dinner but wasn’t sure.

I think i’ll try to do runs for now. If I have time I’ll do the flat spots in my neighborhood – would LOVE to run in the Presidio (it’s one of my favorite spots) but just getting up there would take 20 minutes and I just can’t be away from my desk/ Samson’s BG monitoring that long. If I’m pressed for time maybe I’ll just run to my kids daycare for pickup about a mile away, and just loop around a bit to add some mileage – we don’t have a gym membership so a stationary bike or treadmill is out. I’m a little nervous getting on a bike at this far along in my pregnancy – if I fell it would be pretty bad for baby, plus I will look like a silly Oompa Loompa. Plus my bike needs a tuneup.

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@Sam, I think the thinking on exercise in pregnancy is a little different than it was even 5 or 6 years ago… Back when I was pregnant with Zane we were told the less than 140 heart rate thing.

This time I was told to go at whatever pace I feel comfortable with and to watch for signs that it’s too much. So basically “listen to your body.”

This is the current guideline from ACOG, the American College of Obstetricians and Gynecologists:

“The guidelines advise that pregnant women who habitually engage in vigorous-intensity aerobic activity (ie, the equivalent of running or jogging) or who are highly active “can continue physical activity during pregnancy and the postpartum period, provided that they remain healthy and discuss with their health care provider how and when activity should be adjusted over time” (2). The World Health Organization and the American College of Sports Medicine have issued evidence-based recommendations indicating that the beneficial effects of exercise in most adults are indisputable and that the benefits far outweigh the risks (3, 4).”

The general idea is not to pick up a totally new exercise regimen during pregnancy but I did run prior to being pregnant and earlier on in pregnancy. Not hard and not as far, but still, enough that I don’t feel uncomfortable running and will simply stop and rest if it becomes too intense. I would do brisk walking but because I live in San Francisco, my day already involves the “recommended 150 minutes a week of mild-moderate aerobic activity” in the form of brisk walking, and it clearly wasn’t enough to reduce those fasting blood sugars.


At least for exercise, the heart rate for intensity varies a lot. For some people, a 140 heart rate for 30 minutes would be tough. For others, a 140 heart rate for 30 minutes feels like nothing. So that is one of those general rules that really depends very much for each individual!

That’s why I was trying to give you a way of rating perceived effort. You know - not brutal, but something that feels like it was some effort. It should not be so hard that you dread it, but hard enough that you feel like you did some work.

Another side note, I was born right next to the Presidio and lived there for a while.

Last September I ran along the Golden Gate Bridge, crossing over twice, and then did something I had never done before, I ran on the west side of the bridge, which is restricted to bicycles only. A totally different view. I made it all the way across without getting stopped. One of my favorite days. I will always treasure that memory.


While cardio will drop your immediate BG faster, there is some belief that resistance training is best for increasing insulin sensitivity. My own PCP, who is T2D, has had many discussions with me over the past five years about the worth of resistance training to increase insulin sensitivity. This is what the ADA seems to say:

What We Recommend: American Diabetes Association®

I have not been able to find good research on insulin sensitivity and exercise. Immediate BG drops, of course, are more pronounced with cardio. This is an interesting recent study which concludes that a mix of both is best:,8599,1662683,00.html

But I think its conclusion is somewhat marred by the fact that the combined group had 2x exercise time compared to the others…

Without seeing any more data, my belief right now would be that resistance training is better to increase insulin sensitivity.

As for time of exercise, @TiaG, I can tell you that it is a pain in the neck to deal with post exercise lows when my son exercises in the evening… But I don’t think this will ever be a concern of yours!

Is there something that points to that? The article you linked seems to go the other way:,8599,1662683,00.html

Obviously doing both would lower it more than just doing one. But since this reference seemed to say aerobic lowered more than weight-training, it could also be surmised that doing twice as much aerobic would also be more than effective than the combined aerobic and weight-training.

The ADA article had these two statements, which are somewhat similar in what they mean

  • Aerobic exercise helps your body use insulin better.
  • Strength training (also called resistance training) makes your body more sensitive to insulin

So I am not quite sure if the ADA is saying one is better than the other, or simply saying they both accomplish the same thing.

I think a lot of Endos might recommend strength training for T1D’s because they are worried about lows that come from cardio. Kind of like DM’s Endo telling her to never get in the pool when her BG was below 200!

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This article only evaluated the immediate lowering of BG (we know aerobics better for that), so it does not research impact on insulin resistance.

The ADA link, on the other hand, explicitly mentions insulin sensitivity with resistance training – and my T2D PCP has been hammering the point with me too. But I wish I could find some good articles that prove the point!

Sure, the ADA says that weight-training increases insulin sensitivity, but that was my question

Aren’t those essentially the same thing?

  • “more sensitive to insulin”

  • “helps your body use insulin better”

Only one of them uses the specific keywords “insulin sensitivity.” So, if I look at insulin sensitivity as the criterion, I figure it is what they meant – this kind of activity is (in their mind) better for insulin sensitivity.

Sure, that makes sense. But since I couldn’t distinguish the difference in meaning between those two phrases, I just gathered that they were re-wording the phrase because their editor yelled at them for using duplicate sentences. :smiley:

A side note funny, I noticed that if you google “definition of insulin sensitivity”, one of the first links describes it this way:
“Insulin sensitivity describes how sensitive the body is to the effects of insulin.”

OMG, that’s the worst definition ever!

Circular definition - a definition that is circular

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this is terribly written. I honestly have no idea.:rofl:

Hey Tia, have you been trying anything with exercise, doing it before dinner? Was wondering if that was working for you.

@Eric, yes I have basically been jogging to school when it’s time for pickup around 5:30pm – it’s not really my ideal “workout” but it gets the job done. So far my fasting BGs have been a little lower – typically 79 -86.


Hi there,

I found this topic extremely helpful. I have Gestational Diabetes and just found out about 1.5 weeks ago. I have been able to keep my numbers in the 90s all day if I follow the diabetic diet, however I could not find a way to get my fasting number below 95. I have been getting around 96-98. My dr wants it below 95 fasting. I tried the late night snack and being really really strict with the diet during the day as well, but nothing seemed to work. Yesterday I tried the suggested 30 minutes of aerobic activity for 30 minutes before dinner and this morning my number was 89. hurray! I am going to keep trying this and see how it goes.


Oh, and I wanted to add, I WAS getting 30 minutes of exercise during the day previously and was still getting a number over 95 in the morning fasting. However, it was low intensity walking or swimming. So what seems to make the difference is the higher intensity and when you haven’t eaten in a while, as suggested by Eric to get the fasting number down.


So glad this topic was helpful to you. Let us know what else has worked – I’ve been thinking we need to have some more threads on gestational diabetes, as that’s something so many pregnant women experience.

How long before dinner do you recommend working out. Did you skip an evening snack? I’ve been just having a piece of cheese my numbers are just under 95 at about 90-91 would like to see them lower…I’d prefer not to be on insulin if possible. My numbers throughout the day are very manageable

I did my workouts around 5 pm but maybe it depends on when you wake up and when you have dinner. I tried to eat around 6pm and wake up by 6am almost every day – not my choice, kids wake me up then. (I had my baby 10 months ago so I’m also a little fuzzy on the details.) @Eric I vaguely remember something about 12 hours – is around how long after you work out that your muscles will start pulling glucose in from your blood to restore your glycogen stores?