Chapter 2
IN THIS CHAPTER
Finding out how exercise, food, and aging affect your body with diabetes
Raising insulin action with physical activity (and other factors)
Consulting with your health care provider and establishing training goals
Considering your chances for cardiovascular disease
Having a long, full life despite diabetes/prediabetes
Getting fit can benefit your health, whether or not you have diabetes or prediabetes. Physical activity makes your insulin work better. More effective insulin action usually results in improved blood glucose.
In this chapter, you get guidance on managing your diabetes and improving your health, along with the keys to making goals that stick and help you get fitter and keep fit for life. You also discover when seeing your doctor before getting started on your new fitness goals may be best — such as before you start working out too hard if you’ve been a couch potato recently.
Many people — youth and adults alike — are becoming overweight in large part because they’re failing to engage in enough daily physical movement and making unhealthful food choices. Americans have become a society of overweight, sedentary people. Despite knowing the health benefits of exercise, nearly half of all American adults aren’t active at all, and 70 percent fail to meet the recommended 30 minutes of exercise a day on most days.
Becoming physically active is more than worth the effort because the more sedentary you stay, the greater your risk of dying prematurely. If that’s not convincing enough, think about your daily life. The quality of your life matters even more than just being alive, and staying on the couch increases the chance that you won’t feel as good as you can for much of your (shortened) life.
For people with diabetes, inactivity is even more rampant. If you have diabetes, you may keep yourself from being active because being active can potentially unbalance your blood glucose, or you may be dealing with another health issue. But you have to ask yourself: Do you really want to spend the last 20 years of your life impaired by even more diabetes-related health complications? You can improve your quality of life with diabetes and prevent most health problems by getting off the couch and keeping fit.
Having a basic understanding of what is happening in your body when your glucose levels get high is helpful so you know what you can do about it. Regardless of whether you have prediabetes or diabetes (which I describe in Chapter 1), exercise works to lower insulin resistance and improve your blood glucose management. By combining regular activity with more healthful eating and possibly medications, you can take control of your blood glucose and your overall health.
In short, exercise bypasses the need for insulin to lower blood glucose, even if you’re insulin resistant the rest of the time. That means you have an alternate way to bring glucose levels down without being dependent on your insulin to do it.
During rest, muscles cells depend on insulin to allow blood glucose to enter. Insulin binds to insulin receptors on the surface of individual cells, which starts a series of enzymatic reactions inside the cells that allow glucose to be transported across the cell membrane, thus lowering blood levels.
However, when the muscles are active during exercise, insulin isn’t required to start this reaction. The muscle contractions themselves trigger an alternate pathway that gets glucose from the blood into active muscle without using insulin at all.
Your muscles can continue to bring in more glucose — without insulin initially — for a period of time after exercise (typically 2 to 72 hours, depending on the type of activity done). That helps you lower blood glucose naturally and lasts as long as your muscles are replenishing their carbohydrate (glycogen) stores. Several hours after exercise ends, insulin is back to being the main way to lower blood glucose, but its action is higher than it was before you worked out.
Food and calorie-filled drinks are made up of macronutrients (carbohydrate, protein, and fat) that can be converted into usable energy in the body and micronutrients (like vitamins and minerals) that help your body break down the macronutrients. These macronutrients supply your body with energy, or calories, although each serves a different primary role:
Though each of these nutrients potentially affects your blood glucose in different ways, it’s the carbohydrates you eat that have the greatest impact on the amount of glucose in your blood. The body converts carbohydrates into simple sugars — glucose being the primary one — soon after you eat them, usually within five minutes to two hours depending on the type. Only minimal amounts of protein and fat become glucose after digestion, so they don’t affect your blood glucose nearly as much.
You should check your blood glucose before and after meals to get a feel for how foods, particularly those containing a lot of carbohydrate (such as potatoes, bread, rice, pasta, fruit, fruit juice, and desserts), affect your blood glucose.
When you eat a higher-fat meal, your digestive process is somewhat slowed down, and your blood glucose may not reach its highest point until four to five hours later. What’s more, high-fat foods cause insulin resistance, which, together with slower digestion, may lead to higher blood glucose levels hours after you eat when your muscle, fat, and liver cells aren’t using the insulin in your body properly to lower blood glucose. Many of these options are best considered “get you now, get you later” foods because they can raise your blood glucose at both these times if you are a meal-time insulin user.
Aging by itself causes bodily changes, many of which are independent of disease, even if you remain physically active throughout your lifetime. Diabetes can also cause health complications that are separate from the effects of aging. Sometimes, it’s hard to tell whether your health issues are arising from diabetes or normal effects of getting older. For instance, people without diabetes can develop nerve damage (neuropathy) in their feet, especially if they’re taller.
The changes your body undergoes over time are complex and involve both normal physiological and disease processes. In general, your body experiences very gradual and subtle alterations in how well its different systems like breathing, digestion, and sexual ability function over time.
Human cells apparently can split and reproduce a limited number of times. After your cells slow their rate of turnover, these subtle changes start to accelerate. Unfortunately, such effects are often inseparable from the onset of diseases like heart disease and cancer.
However, much of what people attribute to getting older — such as muscle atrophy or loss of flexibility in joints — results from disuse over time, not just from aging. At one point, researchers believed that greater insulin resistance was practically inevitable with aging due to a natural loss of muscle mass over time. But more recent studies have shown that master athletes are as insulin sensitive as younger individuals who are physically active, and they also have better insulin action than people of any age who are sedentary and either of normal weight or obese. Being sedentary can lead to insulin resistance even if you stay thin, most likely due to dual losses of muscle from aging and inactivity.
Having diabetes or prediabetes — especially when your insulin resistance is high or your blood glucose is poorly managed — can cause premature aging, accelerated heart disease, and other chronic illnesses. In such cases, regular exercise can keep you looking and feeling younger for longer and even greatly lower your risk of getting any health complications.
Getting in regular workouts has an immediate effect on your overall physical condition by slowing aging and preventing diseases that can shorten your life span or rob you of your vitality as you age. For example, bone density peaks somewhere around 25 years of age, after which time bones may start to lose some stored calcium and other minerals over time — unless you stress the bones with physical movement and stimulate them to retain more minerals. A sedentary lifestyle, conversely, leads to thinning bones, the potential for fractures, and a reduced quality of life.
Keeping fit is more important to living well than you can possibly know. In fact, it’s likely the most critical behavior you can adopt to impact how well your insulin works in your body. Insulin resistance is linked to multiple health problems, including type 2 diabetes, high blood pressure, reduced blood flow, inflammation, heart disease, and many more. A lack of physical activity is linked directly to defects in the action of insulin primarily at the level of your muscle and fat cells.
The two main body tissues that are sensitive to the effects of insulin are your muscle cells and adipose, or fat, tissue. Obesity is associated with an accumulation of stored fat inside both muscle and adipose cells. Muscle is an important storage site for excess glucose and carbohydrates. But when your muscles get filled with excess fat or carbohydrates, they become less sensitive to insulin, and your pancreas must release more insulin to have the same effect (or if you need insulin, you’ll need to take higher doses).
A third tissue also responsive to and affected by insulin is your liver. This organ is responsible for making sure you have enough glucose in your blood at all times. It can both store and release glucose to keep levels constant.
In some people with diabetes, the liver becomes insulin resistant and releases too much glucose, especially overnight when they go for long periods without eating. Gaining a lot of excess fat within your abdomen (called visceral fat) and within the liver itself can contribute to an insulin resistance there.
Interestingly, your fat cells usually remain largely responsive to insulin even when your muscle cells become resistant, and much of your excess blood glucose can be converted into storage fat. When the carbohydrates you eat end up spiking your blood glucose, the rise causes the release of more insulin and ultimately more fat storage in fat cells and likely your liver.
Think of your muscles as a glucose tank, a place to store the carbohydrates that you eat and don’t need to use right away, as shown in Figure 2-1. When you exercise regularly, you use up glycogen stored in the muscles and have room to put carbohydrates back in after you eat. If the glycogen stores are already full because you’ve consumed too many carbohydrates or exercised too little, your muscles can’t store more carbohydrates after you eat, and you’re insulin resistant. This state is reversible with exercise.
Physical activity isn’t the only factor that can improve your insulin action, however, and most of them you have some control over. Addressing these factors can raise your body’s insulin action and consequently reverse prediabetes or improve diabetes management.
How do you know whether you need to see your doctor before you start to exercise? The bottom line is that you probably don’t need a checkup before engaging in easy workouts or moderate activities like brisk walking, but having one before you begin more vigorous workouts is a good idea. It also depends on your age, your general health, and your current physical activity level.
If your blood glucose has been in check, you’ve already been physically active, and you don’t have any serious diabetic complications, then exercise away. If you’re very active, getting an extra checkup before you replace your current exercise regime with another exercise routine is definitely unnecessary. Having regular visits to your doctor or other health care provider, though, is a good idea for anyone who has diabetes or prediabetes.
If you have a checkup, get your blood pressure, heart rate, and body weight measured, and ask whether you need to do an exercise stress test, which usually involves walking on a treadmill or riding a stationary bike for around ten minutes. Note: The American Diabetes Association recommends an exercise stress test only if you’re over 40 and have diabetes or if you’re over 30 and have had diabetes for 10 or more years, smoke, have high blood pressure, have high cholesterol, or have eye or kidney problems related to diabetes. Above all, this recommendation applies only to people planning to do vigorous training that gets their heart rates up high. If you’ll just be doing mild or moderate aerobic activity or resistance training, such extensive (and often expensive) testing may not be necessary.
Your checkup may also include a urinalysis, kidney function testing, serum lipid evaluation, and electrolyte analysis, along with screening for any diabetes-related complications, including heart, nerve, eye, and kidney disease. Though such health problems don’t usually keep you from exercising, doing so safely and effectively with them may require special accommodations or precautions.
Health and training goals for most people revolve around lowering insulin resistance, managing diabetes and blood glucose levels, and losing weight and keeping it off. Regardless of your motivation for keeping fit, your overall health and your diabetes management can both benefit immensely from any physical activity that you do regularly.
Preventing your blood glucose from getting too low or too high during exercise is critical to exercising safely and effectively, particularly if you use certain diabetes medications or insulin. Whenever you start doing new or different activities, plan on testing your blood glucose to determine how your body reacts, including before and after exercise and even sometimes during a workout.
You should have a target for your blood glucose, both for certain times of day and for average levels over two to three months. Exercise has a short-term effect on your blood glucose (see the earlier section “Recognizing why exercise training is critical”), but it also has a longer lasting benefit: Your insulin (natural or injected) is more effective. With regular exercise, better insulin action helps lower your blood glucose levels, improve your diabetes management, and prevent health complications.
Table 2-1 gives the recommended targets for all your blood glucose numbers. It includes what you should aim for both before and after meals, as well as what a good average glucose (A1C) would be and how that corresponds to the values you see on your blood glucose meter.
TABLE 2-1 Recommended Blood Glucose and A1C Targets
Glucose Measure |
Goals |
Blood glucose (before and after meals) ADA goal – not AACE |
70–120 mg/dL (3.9–6.7 mmol/L), before meals |
< 180 mg/dL (10.0 mmol/L), 2 hours after meals |
|
A1C (glycated hemoglobin) |
American Diabetes Association goal: < 7.0% |
American Association of Clinical Endocrinologists goal: < 6.5% |
|
Average glucose (from A1C values) |
American Diabetes Association goal: < 154 mg/dL (8.6 mmol/L) |
American Association of Clinical Endocrinologists goal: < 140 mg/dL (7.8 mmol/L) |
Unlike a finger stick glucose, which represents only one point in time, an A1C value gives you an idea how your blood glucose has been averaging during the past several months, particularly the previous four weeks. Current recommendations suggest you should aim for a value of 7 percent (equivalent to average blood glucose levels of 154 mg/dL) or less. Some groups recommend a goal of less than 6.5 percent (non-diabetes values usually fall in the range of 4.0 to 5.6 percent). The lower your A1C is, the better it generally is for your health. If you have diabetes, you should routinely get your A1C tested every three to six months.
You can convert your A1C value into an equivalent glucose reading (shown in Table 2-2) to make it more meaningful when you see it. This average glucose tells you what your glucose has been in the same values you’re used to seeing on your blood glucose meter.
TABLE 2-2 A1C Converter to Average Glucose Equivalent
A1C (%) |
Average Glucose (mg/dL) |
Average Glucose (mmol/L) |
5.0 |
97 |
5.4 |
5.5 |
112 |
6.2 |
6.0 |
126 |
7.0 |
6.5 |
140 |
7.8 |
7.0 |
154 |
8.6 |
7.5 |
169 |
9.4 |
8.0 |
183 |
10.1 |
8.5 |
197 |
10.9 |
9.0 |
212 |
11.8 |
9.5 |
226 |
12.6 |
10.0 |
240 |
13.4 |
10.5 |
255 |
14.1 |
11.0 |
269 |
14.9 |
11.5 |
283 |
15.7 |
12.0 |
298 |
16.5 |
13.0 |
326 |
18.1 |
14.0 |
365 |
20.3 |
Many people with diabetes also have elevated levels of blood lipids (fats like triglycerides and cholesterol) that are associated with an increased risk for heart disease and stroke. Having diabetes by itself already increases your risk of having cardiovascular disease.
You likely can reach most of your health goals by adopting a physically active lifestyle and making better food choices. Losing weight usually helps improve blood lipid profiles, although aerobic exercise training without significant weight loss has been shown to improve metabolism, cholesterol levels, fasting glucose, and more in people with type 2 diabetes. Eating more fiber and fewer refined foods can also improve these health variables. You may be able to reduce or eliminate your need for cholesterol-lowering medications like statins.
People decide to become more physically active for all sorts of reasons. Some are new to exercise and realize that making important lifestyle changes may allow them to manage type 2 diabetes, reverse prediabetes, and avoid diabetes medications early after their diagnosis. Others with type 1 diabetes are suffering from “double diabetes” due to being sedentary and gaining weight, and they may choose to benefit from starting an exercise program.
Many people are already active and want to train for a specific event, such as a 10K race or a half-marathon, and they need to increase their fitness to cross the finish line in style. Others may simply want to try a new sport or activity or get involved in cross-training to raise their level of fitness.
All these reasons for getting more physically active are appropriate. There is no wrong reason for getting and keeping fit when you have diabetes or prediabetes. (In fact, everyone should set some fitness goals — even if they don’t have diabetes.) Just make sure your goals are realistic and achievable so that you don’t get discouraged.
As I note earlier in the chapter, people with diabetes have a higher risk of developing cardiovascular disease. If you have additional risk factors for heart disease, your chances of having a heart attack or stroke during exercise are greater. For that reason alone, you should figure out what your risk factors are. The major cardiovascular risk factors include the following:
The more risk factors you have, the greater your chance of developing heart disease, stroke, or peripheral artery disease. You can’t really do much about some of these risks (like age or biological sex), but others you can. For example, getting rid of some of the fat inside your belly through exercise usually helps more than just lowering your overall weight with dieting.
Having an elevated degree of a particular risk increases your overall chances, too. For example, if your total cholesterol level is 300 mg/dL, your risk is higher than the risk for someone whose cholesterol runs 245 mg/dL, even though both numbers are in the same high-risk category. Likewise, you can stop — or at least reduce — cigarette smoking and lower your risk, given that the relative risk of stroke in heavy smokers (defined as smoking more than 40 cigarettes a day) is twice that of light smokers (fewer than 10 cigarettes a day).
Despite any horror stories you may have heard about diabetes and its potentially bad effects, you can live long and well with any type of diabetes or prediabetes. You just have to learn all you can about what to do to stay healthy. Most of the advice from long-living people with diabetes about how to live well applies to everyone — not just to those with diabetes.
Get started today on improving your fitness and also follow these tips for optimal health and a long life:
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