Many of us find that low-carbohydrate (LC) diets work the best to control our blood glucose (BG) levels. Many of us also find that LC diets control our hunger as well, which is very important when you want to lose weight.
And although you can lose weight on various types of diets if you control your calorie intake, controlling your calorie intake can be difficult when you’re ravenously hungry most of the day. That happened to me. I lost weight on a low-calorie, low-fat diet when I was diagnosed, but I was ravenous the whole day and finally decided I couldn’t live with this for the rest of my life and gradually switched to a LC diet, and the hunger disappeared.
Some people don’t feel ravenous on a low-fat diet, and for them any type of diet works for weight loss or simply for health maintenance. But there’s evidence that people with insulin resistance, which means most of us as well as people with metabolic syndrome, often a precursor to type 2 diabetes, do better on LC diets. In fact, one paper suggests that doing better on a LC diet might be considered a definition of metabolic syndrome.
I think the key here is that when you have insulin resistance, your BG levels can go very high after eating carbs, and then they come down fairly fast until you have overt diabetes. And I think this rapidly falling BG level triggers hunger. It’s logical. If your BG is falling fast, the body wants to correct it before you go low instead of waiting until you’re low, when it would take 15 or 30 minutes to correct the low, and by that time you could already be alarmingly low.
When I did mini oral glucose tolerance tests (OGTTs), I found I got ravenous just after the peak BG level, as illustrated in Figure 6 in my book The First Year: Type 2 Diabetes. If you can avoid those peaks and rapid falls, your hunger should abate.
People without insulin resistance don’t see this effect, because their BG levels don’t usually go as high after eating.
Thus, for people with insulin resistance, LC diets are beneficial. However, one thing many people on LC diets don’t realize is that when you’re on a LC diet, you become more sensitive to carbs. This means that an amount of carbs that wouldn’t make your BG levels go up much if you weren’t on a LC diet can make them go up a lot if you’re not.
The most extreme example of a LC diet is starvation, zero carbs as well as zero anything else. People who are starving will test diabetic on OGTTs even if they’re not. So that’s why when you take an OGTT, for example, if you’re pregnant, they tell you to eat a lot of carbs for 2 or 3 days before the test.
Why is this true? One reason is that when you don’t eat carbs, your body stops producing the enzymes that metabolize carbs so they can remain in your bloodstream longer. Another reason is that when glucose is in short supply, the body tries to conserve it to use in the brain, which does need some glucose. One way to do this is to increase insulin resistance in the muscles, which can get their energy from fat (and often prefer to).