I’ve got a metaphor for you.

It’s a pretty elaborate metaphor, and it will take me some time to explain it. But please bear with me, because it’s a very useful metaphor. If you can get this idea into your head, and keep it there, you will be much better equipped to handle the challenging task of keeping your glucose under control.

So here goes: imagine that you are washing dishes in your kitchen sink. The sink is about half full of water, and you have some dirty dishes soaking in it. Also, you have the faucet running. You scrub a dish, hold it under the faucet to rinse it off, put it aside on the drying rack, and then you fish the next dish out of the water to scrub and rinse it. As this system seems to be working well for you, you would like to keep things pretty much as they are. That is, you would like the water level in the sink to stay about where it is, neither rising nor falling.

But does it do that? While you’re washing your dishes in this way, what happens to the water level in the sink?

Well, that depends. If the drain is completely plugged, the water level will rise steadily so long as the faucet continues to flow — and eventually the water will overflow the sink and spill all over the kitchen floor.

On the other hand, if the drain has no stopper in it, and isn’t being obstructed by the dishes in the sink, and it’s draining fast, the water level in the sink will fall steadily — until there is no standing water in the sink, and the dishes are no longer soaking. Those are the extremes of the situation: the sink overflows, or the sink empties.

Now, suppose that there’s no stopper in the drain, but it’s a slow drain, or it is partly blocked by the dishes in the sink. Now things get complicated. The water is draining out of the sink, yes... but is it draining faster than the water is pouring in from the faucet, or slower?

If the sink is not draining quite as fast as the faucet is flowing, the water level in the sink will gradually rise. It won’t rise as fast as it would if the drain were completely blocked, of course. But if you continue adding water to the sink faster than it can drain out, the end result will be the same: sooner or later it will overflow; it’s just a question of when. On the other hand, if the water is draining a little faster than it is pouring in, the water level in the sink will gradually fall, until there is no standing water in the sink. If you manage to set up a situtation where the faucet is flowing and the drain is emptying at the same rate, the water level in the sink will stabilize, neither rising nor falling. This is the ideal outcome — not necessarily easy to achieve.

Unless you have lived a very sheltered life indeed, I would venture to say that you have actually grappled with this situation once or twice yourself. Experience has taught you, therefore, that there are two things you can do to control the water level in the sink: (1) you can adjust the rate at which water is draining out of the sink, by adjusting the degree to which the drain is obstructed, or (2) you can adjust the rate at which water is pouring into the sink, by opening the faucet a little wider or shutting it down a little.

So the real issue here is a problem of controlling the rates of two independent processes. Water is flowing into the sink, and water is draining out of it. You don’t want the faucet to be flowing faster than the drain is draining. At least, you don’t want that to happen for very long. It’s okay to turn the faucet on full blast for a little while, because the sink is only going to back up so much over a short period. But whenever the faucet rate is higher than the drain rate, the water level in the sink is rising. You can’t allow that situation to continue for very long, if you want to avoid overfilling the sink.

Of course, you don’t want to empty the sink, either. Ideally, you want to have a few inches of water in the sink, and you want the faucet and the drain to be flowing at the same rate, so that the water level stays where it is.

So here’s the metaphor...

This metaphor has some useful things to tell us about how to live with diabetes.

Making adjustments

Having type 2 diabetes is equivalent to having a slow drain, so your sink will be constantly at risk of overflowing if you don’t make every effort to (1) open the drain wider, at least to the extent that this is possible in your case, and (2) use the faucet with caution.

Keep in mind that this problem is all about rates: the rate at which glucose pours in, and the rate at which glucose drains out.

You want the drain to be open as wide as you can get it, so that it pours glucose out reasonably fast. You need to do everything in your power to increase your sensitivity to insulin, because this is what widens the drain. It may surprise you to hear that there is anything you can do about this, but there is.

However, once you have developed type 2 diabetes, there are probably some limits on how wide you will be able to open that drain. For this reason, you must also do what you can to limit the rate at which you are pouring glucose into the sink. You must be very cautious about turning the faucet wide open. Non-diabetic people, whose drains work just fine, can afford to open the faucet as wide as they want, whenever they feel like it. You cannot.

Of course, you don’t really want the sink to empty itself completely; you have to have some glucose just to survive. But emptying it completely is not much of a risk for those of us with type 2 diabetes, because we have chronically slow drains that can never be completely cleared. For people with type 1 diabetes, the problem is more complex; their drains are easily cleared, so they are just as much in danger of emptying the sink (by taking too much insulin) as they are of overfilling it (by taking too little). If you have type 2 diabetes, your drain is always at least a little slow, and your sink is often fuller than you want it to be, so your main concern is avoiding an accidental overflow.

So, if glucose control is all about adjusting the rate at which glucose drains out, and the rate at which it pours in, how do we unclog the drain, and how do we adjust the faucet? There is a lot to be said about that question. The simple answer is that opening the drain is achieved by means of exercise and weight loss, and that turning down the faucet is achieved by means of dietary restraint.

If those two options fail you, there is a third, but I would consider it only as a last resort: get hold of some caustic chemicals and dump them into the drain to clear it (that is, have your doctor prescribe pills or shots for you). The time to reach for this option is when no other option is working for you. There are good reasons for avoiding the Drano approach if you can. The chemicals are expensive, they’re not quite safe, and even if you don’t screw up and do serious damage with them, using them over long periods might burn holes in your pipes anyway. You’ll be far better off in the long run if, instead, you make careful adjustments to the faucet and make regular use of the plunger.

Perhaps, some day, you will be forced to pour something corrosive down your drain, but it’s a good idea to put that day off if you can.

Opening the drain

Let’s talk about the things you can do to increase the rate at which glucose leaves your blood supply. That is, the things you can do to unclog the drain so that the glucose flow freely through it.

Weight loss and why it helps

Well, actually, nobody knows why weight loss helps -- except in the narrow sense that excess body fat somehow or other promotes insulin resistance. We don't know how excess body fat promotes insulin resistance (the mechanism remains unexplained), but for practical purposes it is enough to know that it does, and that getting rid of excess body fat tends to correct the problem.

I'm not necessarily claiming that losing weight is enough, by itself, to make the problem go away, entirely and permanently. There is a strange intertia involved in insulin resistance: once your cells have become insensitive to insulin, they are oddly reluctant to go back to the way things were, and you have to work hard at restoring their insulin sensitivity.  If you are overweight, you need to shed the excess pounds, but that alone probably won't be enough.

Exercise and why it helps

Exercise “opens the drain” in three ways:
  • It causes a rapid transfer of glucose from the bloodstream to muscle tissue, largely by mechanical action rather than insulin-triggered absorption. Learn to think of the contraction and expansion of muscle fibers as a kind of plunger action, loosening up the clogged drain and drawing the glucose down into it.
  • Exercise causes physical changes to occur in cells and cell membranes which make the cells more sensitive to insulin (and therefore causes the cells to absorb glucose faster). These changes are not permanent, but they are powerfully present immediately after excersice, and they fade gradually; they continue to have an effect for 24 to 48 hours. If you exercise daily, the effect is permanent for all practical purposes.
  • Exercise causes muscle tissue to grow; this increases the body’s total capacity for sugar absorption. Think of it as equivalent to widening the drain pipe. Also, muscle tissue is replaced faster if you use it a lot, and this seems to make the muscles more insulin-sensitive even if they aren't significantly larger.
Although exercise works, it isn’t regarded by everyone with great enthusiasm. A lot of people hate it, or at least would prefer not do it, and I think it is safe to say that a lot of people with type 2 diabetes are in that camp. Well, too bad: you have to do it, whether you want to do it or not. Therefore, the sooner you let go of the assumption that it matters whether you want to do it or not, the better off you will be. I admit it's not an easy assumption to let go of; it took me about 2 years (but maybe you're less rigid than I am).

Turning down the faucet

Because glucose plays such an important role in meeting the body’s energy needs, the digestive system is designed to be very, very good at turning the food you eat into glucose. I don’t just mean the sugars and other carbohydrates that you eat; your body is also capable of turning some of the fat and protein you eat into glucose. Generally speaking, if you can digest it, your body can obtain glucose from it.

However, the amount of glucose you get from different foods, and the rate at which you get it, varies a lot. Therefore, adjusting the faucet is not just a matter of controlling how much you eat. Choosing your foods is also important. (However, I feel a little reluctant to say this, because most people have the mistaken idea that if they choose the right foods it won't matter how much they eat. Not so!)

  • Only about half of the protein you eat is converted into glucose (the body has other uses for the rest of it), and the process takes something like four hours.
  • Only a small fraction of the fat you eat is converted into glucose, and the process takes even longer than for protein (perhaps eight hours).
  • All of the carbohydrate you eat is converted to glucose, and rapidly. Starches take about an hour. Simpler sugars take only 15 to 30 minutes, which is why athletes use sugar (and even pure glucose) for quick energy.
Because these different components of food are digested at different rates, the faucet continues to flow for several hours after a meal, but it starts out fast (because of the carbohydrates) and then slows down considerably as the proteins, and finally the fats, make their smaller contributions.

Limiting the impact of carbs

The biggest issue, in terms of glucose management, is carbohydrate. Dietary carbohydrate opens the faucet wide, so that it pours glucose into the sink at a rapid rate. Simple sugars cause the most rapid flow rate. With starches, the faucet doesn’t flow quite as fast, but it flows longer. The total amount of glucose dumped into the sink is the same regardless of what kind of carbohydrate you have consumed, but the simplest carbohydrates flow the fastest, so that you get the whole amount in a shorter period of time. The only kind of carbohydrate that doesn’t open the faucet at all is the category of indigestible carbs, known collectively as “fiber”. But most of the carbohydrate in human foods is digestible, and all digestible carbohydrate is converted entirely into glucose.

The biggest issue then, in terms of faucet adjustment, is the carbohydrate content of your meals. Your drain would have to be very badly clogged indeed for the protein and fat content of a meal to back up the sink, but carbohydrates throw the faucet wide open, and carry a big risk of an overflow.

Exactly what your carbohydrate limit needs to be is a very complicated question — and also, in a practical sense, a very simple one. There's no knowing what physiological complexities might go into determining the amount of carbohydrate that you, personally, can consume in one meal without overfilling the sink. Fortunately, you don’t need to know how to work this out on a theoretical basis, or how to plug your individual numbers into some monster equation. A purely experimental approach will do.

Use a glucose meter to test your blood glucose level an hour after a meal. If you do this enough times, and in each case you know about how much carbohydrate you consumed in that meal, it will pretty soon become clear to you how much carbohydrate you can “get away with”. Yes, this will vary somewhat with circumstances, because your sensitivity to insulin tends to fluctuate (the drain is less clogged on some days than others) but it doesn’t vary so much that you can’t establish good guidelines for yourself.  

If you discover that anything over 60 grams of carbohydrate (or 50, or whatever) gives you an unacceptable glucose spike an hour after a meal, then you need to get in the habit of choosing meals that keep you under that limit. It may be that your insulin sensitivity will improve later, and you will be able to try some cautious experiments to see if your limit has perhaps gone up. One of the nice things about doing a lot of exercise is that it gives you some hope of tracking a long-term trend that is going in a positive direction, not a negative one. People who rely on pharmaceuticals to manage their diabetes tend to see a gradual erosion, not a gradual improvement.

Fat and digestion

Dietary fat has an interesting secondary effect on blood glucose. Fat in a meal tends to slow down the digestive process, particularly the emptying of the stomach into the small intestine. This means that a meal which contains a substantial amount of fat will not “open the faucet” as wide as a fat-free meal providing the same number of calories.

Pure sugar produces a sharp spike in your blood glucose; sugar accompanied by fat produces a more gradual rise which doesn’t reach the same height. You need some fat in your meals, if you have type 2 diabetes. (A bagel with peanut butter on it wil probably not produce as big a glucose spike as a bagel without peanut butter on it, even though there is carbohydrate in the peanut butter.)

Be wary of the popular assumption that “fat-free” necessarily means “good for you”. It may be good for somebody, but you are probably not that person.  

Rise and fall

Because carbohydrates are digested rapidly, they make the faucet flow very fast. However, they don’t keep the faucet flowing very long. Carbohydrates tend to cause a steep increase in blood glucose, followed by fairly steep decline. The decline, at least, sounds like a good thing, but in an indirect way it can actually be a problem.

When your glucose level drops at a rapid rate, it tends to make you feel hungry, and this is true even when your glucose level is still high. It is the rate of change in the glucose level, not the level itself, that triggers the hunger. Therefore, a sudden rise and fall in glucose (which is the typical result of eating a meal that is mostly carbohydrate) can make you feel hungry, perhaps very hungry, in an hour or two. Most of us feel enough temptation to eat between meals as it is; the aftermath of a high-carb meal can make that temptation impossible to resist. If you often feel that you can’t make it from lunch to dinner without a snack, that feeling could be a sign that your lunch should not include quite so much carbohydrate.