During my experiments with fasting, I have had had many questions about blood sugar levels. I wanted to know if I was doing myself any harm or what I should be careful about. It became quickly apparent to me that I had almost no understanding of what “blood sugar” actually means or how sugar processing works in the body. It turns out blood sugar has a lot to do with weight maintenance and the more we know about blood sugar levels and work to control them, the better equipped we are to handle our weight challenges.

Below is a quick summary of some of the questions I had about blood sugar and a simplified, short answer, along with links to additional sources of information if you are curious.

What does “blood sugar” mean?

Blood sugar is a simplified term that refers to the amount of glucose in the blood. Glucose is the main source of food and energy for our cells. When you eat carbohydrates (grains, sugars, starches, etc.), the body breaks them down into several components, one of which is glucose. Glucose levels start to rise as soon as 15-30 minutes after eating carbohydrates, faster for liquids like juice and sodas and slower for solid foods like pasta and fruits. Glucose alone is not enough, however. If there is no insulin in the body, the glucose cannot be used by the body.

What does insulin do?

Insulin regulates the absorption of sugar (glucose) by cells. If insulin levels are high, glucose enters the cells and your blood sugar level drops but excess sugar to the cells is stored as fat. If insulin levels are low, too much sugar backs up into other parts of the body where it is not needed and causes the body to malfunction in various complex ways.

In diabetes, insulin is malfunctioning in what way?

Both types of diabetes involve the body not having enough functioning insulin, either because the pancreas does not produce enough insulin (Type I) or the cells in the body don’t respond to available insulin (Type II). In many Type II diabetics, a high blood-sugar raising diet over a sustained period of time results in the body producing so much insulin that the body becomes resistant to its effects.

If you are trying to lose or maintain weight, where do you want your insulin levels to be?

Dieters want low blood sugar and low insulin levels because they want as few sugars as possible being converted to stored fat and they want the body to burn stored fat as a source of energy. The most common medicines taken by diabetics show how insulin and glucose levels affect weight. For example, glucose inhibitors allow diabetics to eat blood-sugar raising foods with fewer blood sugar (and fat-building) consequences. This can lead to minor weight loss in many people. In contrast, often when diabetics take insulin weight gain is seen as the body is using more of its available sugar (and converting it to fat).

How does diet affect insulin levels?

While avoiding sugar is a good place to start to lower your insulin levels, it’s a lot more complicated than that. Just about anything that tastes good will raise your insulin levels. Both carbohydrates and proteins raise insulin levels. The primary foods that don’t elevate insulin levels much are things like salad greens and olive oil.

How does exercise affect glucose levels?

Exercise has a somewhat magical effect on people with blood sugar regulation problems. Exercise has the ability to open up blocked pathways to use glucose in the body that might be blocked by improperly functioning insulin. Some commonly administered diabetes medicines in effect work like an “exercise pill,” providing this glucose uptake benefit of exercise without the patient actually having to exercise. In a person with normal blood sugar, exercise combined with normally functioning insulin clears excess blood sugar from the body faster than insulin alone.

What are some dieting strategies to control insulin and blood sugar?

There are many strategies to control blood sugar and promote weight loss. One school of thought is to try to keep your blood sugar constant at all times by eating regular, small meals. Some think that this will prevent you from indulging in high carbohydrate foods and keep your weight in check. The key to success in this strategy, however, is that you make sure your small meals are things like vegetables and lean proteins and not too many carbohydrates. Dr. Oz. provides one example meal plan for this strategy. Fasting is an extreme form of blood sugar regulation. Rather than keeping your blood sugar constant, the fasting diet will swing you from highs on your non-fasting days to extreme lows on your fasting days. Fasting works in part because the blood sugar gets very low at least part of the time and therefore promotes some amount of fat burning.

What did I take away from this information?

It helped me to know the above information because it gave new insight as to why diet and exercise are so important. Often when we hear a doctor or other health professional recommend “diet and exercise” to us it almost feels like a cop-out, like they have no idea how to deal with our “real” problems so they default to generic “diet and exercise” recommendations. This information highlighted to me that diet and exercise is really quite a complicated process with many effects on the body. Even though we all get the same “diet and exercise” recommendations it may be for very different reasons particular to our own body chemistry.

Before I get back to my own weight maintenance experiment, in my next post, I will discuss weight loss factors specific to women and why our weight control issues have a layer of complexity that men don’t face.