“Lose some weight” is probably one of the most common pieces of medical advice, particularly in this country (where a full 37% of adults technically qualify as “obese”). The benefits of losing weight are well known — weight loss cuts down on heart disease, extends life expectancy, lowers the likelihood of developing Type 2 diabetes, lowers the risk of stroke and heart attack, and on the list goes. And for anyone who already has diabetes, weight loss can be highly beneficial in improving blood glucose control. Lower BMI (body-mass index, a measure of weight relative to height) is associated with lower insulin requirements for those of us with Type 1, and lowering or sometimes even eliminating the need for injected insulin for those with Type 2. Furthermore, the insulin we DO inject works more efficiently as we lower our BMI, since decreasing excess body fat is known to improve insulin sensitivity.
I could go on, but I think the point is pretty clear — reaching and maintaining a healthy weight is a universally good idea, and one that all of us with diabetes should strive for (and I should point out here, I am part of that 37% of Americans I mentioned above, so I know how hard it can be to achieve that healthy weight — it has become a central focus for me lately, in fact, and the end goal is a long journey ahead of where I stand today). But reaching that healthy weight can be a complicated thing for anyone taking insulin. The simple version of what complicates matters is this: Exercising lowers blood glucose; low blood glucose requires ingesting glucose; that ingested glucose is caloric; adding extra calories slows weight loss. So here we are, engaging in an activity specifically to help us get in shape and lose weight, but that very activity is forcing us to take in sugar, partially defeating (but not fully defeating — more on that later) the purpose of said activity. Ah, diabetes, you little devil!
How can we defeat this cycle? Well, we can’t completely defeat it, but we can work with it and minimize it. First, let’s define the problem a little more in depth here. The problem is that when we exercise, our bodies burn through glucose. In someone who hasn’t injected insulin, the body starts to burn fat when the available glucose in the blood and muscle stores is insufficient. At the same time, the body stops sending insulin into the bloodstream. But injected insulin can’t be removed from the bloodstream, and so when OUR blood sugar is burned through, we will go into hypoglycemia (low blood glucose) because the insulin we injected continues to move blood glucose into the cells. The effect on our weight loss goal is twofold. First, the body isn’t switching over to burning pure fat as quickly because that injected insulin is still supplying the cells with glucose. Second, because that injected insulin is pushing us too low, we need to ingest more glucose, further ensuring we’re getting less of our energy from burned fat and instead getting it from the glucose we just ate!
What I just described is the short-term issue. There’s also a long-term trend to manage. You see, for all of the above trouble, exercising regularly will help us lose weight, just at a potentially much slower pace (if we don’t find ways to minimize those effects). After all, it does increase our metabolism and minimizes insulin resistance (even before significant weight loss — exercising regularly lessens insulin resistance on its own). This all leads to a lowering of our need for long-acting (or for pump users, basal rate) insulin. This is great long-term (there are a number of benefits to lowered dosing of insulin), but it also means that until we establish our new baseline insulin needs, we will have too much insulin in our system all the time, not just when we exercise!
To give you an example from my own life, I’ve been riding my bike to work almost every day for the past two or three weeks. It’s about a 9-mile one-way trip, so it’s roughly 18 miles, four days a week. I also try to get in another similar ride during the weekend. This has been great — I have more energy, I’m feeling better, and I’m even losing a LITTLE bit of weight. But I’ve also been low constantly! My metabolism is running at a higher rate at all times (the effects of exercise on blood glucose last a solid two to three days for me, on average — of course the intensity is not the same as during exercise, but the effect does linger) and my body is making much more efficient use of the insulin I’m injecting. I’ve been slowly lowering my long-acting insulin doses, but it’s a work in progress and involves a bit of trial and error.
So, now that we understand what the issues are, let’s talk about a few solutions. First off, it should be said that even if you do find yourself ingesting extra glucose while exercising, that doesn’t mean physical activity won’t have any effect on your weight. Furthermore, exercise is universally good for the body in many more ways than simply helping it shed pounds. So don’t throw away the idea just because the weight comes down more slowly for us Diabetians!
For the short-term issue of hypoglycemia during exercise, pump users have a big advantage over those of us using injections. A pump user can lower the base rate for exercise periods so that blood sugar doesn’t drop so low. With your provider’s input, consider simply lowering the base rate about an hour or two before exercise begins (since the effect takes a little to kick in), and raising it back afterward. You might still go low during exercise if it’s strenuous, but you won’t need as much glucose. If you’re on injections, you don’t have this option. However, I have found that if sugar is taken before exercise, with the aim of raising blood glucose a little on the higher side — say to 140 or 150 — and then burned through during the course of exercise, the amount taken will tend to be less than if sugar is taken during exercise after glucose has already dipped. I might need 20 grams of glucose before I bike to stay on track throughout my ride (I’ll start around 140 and probably slip down to 70 or 80 at the end of the ride). But if I start around 90, I might need double that amount, taken a few times during the ride, to keep bringing my blood sugar back up after it has fallen too low. Second, if blood glucose is dipping during exercise, energy level dips right along with it — which means you won’t be able to exercise as vigorously. So being preemptive about it helps us burn more calories thanks to a more vigorous workout!
For the long-term issue of needing to lower the base rate, pump users once again have a slight advantage. Lowering the basal rate is a few pushes of buttons for you guys. It’s relatively easy to adjust basal rates in response to changing insulin needs (with your medical team’s assistance, of course!). For those of us on injections, it’s a matter of slowly “notching down” over a period of time until we land where need to be. You might need to notch down by one or two units every day or every other day for a while until blood sugar stabilizes. The point here is to keep it gradual — suddenly lowering by too much and then seeing numbers RISE puts stress on your body as it yo-yos too much, and it makes the whole thing less controlled than it could otherwise be.
So let’s get out there and exercise. The benefits are too many to count, and in spite of the challenges it can pose to blood glucose management in the short term, the long-term effects are nothing but good for us Diabetians!