Dear Doctors: We keep hearing about Type 2 diabetes, and I’m embarrassed to say, I don’t actually know what it is. What does it do, and how do I know if I have it?

Dear Reader: To understand diabetes, we should first talk about glucose. That’s the sugar our bodies make from the foods that we eat, and which our cells use as their main source of fuel. Glucose travels throughout the body via the blood, which is why it’s also often referred to as blood sugar. However, it’s not immediately available to the cells. That’s where insulin, a hormone manufactured by the pancreas, comes into play. Insulin helps transport glucose from the blood into the cells, where it can be used as energy.

When someone has diabetes, it means that the insulin part of that energy equation isn’t working properly. Either the body isn’t manufacturing enough -- or any -- insulin, or it isn’t responding properly to the insulin that is present. That leads to blood-glucose levels that are too high.

Over time, high blood levels of glucose are dangerous. Adverse health effects include damage to the circulatory system, vision problems, nerve damage, stomach or intestinal problems, slow healing, kidney disease and an increase in the risk of heart disease and stroke. Extremely high blood sugar levels can lead to coma, and even death.

In Type 1 diabetes, the pancreas makes little or no insulin. It often develops early in life, but can occur at any age. This type of diabetes is managed with diet and exercise, plus the use of medications and insulin.

Type 2 diabetes, once referred to as adult-onset diabetes, often develops later in life. It occurs when the body doesn’t make or use insulin well. Type 2 diabetes often begins as insulin resistance, which is a condition in which the body stops responding properly to the insulin in the blood. This leads to a loss of the ability to control blood sugar.

Some people can manage Type 2 diabetes with diet and exercise alone. Others may also need medication or insulin to keep their blood sugar in control. Medication needs often change over time, so it’s important for everyone with diabetes to have medical care.

Symptoms of Type 2 diabetes often develop gradually. They include persistent fatigue, increased thirst and urination, blurry vision, frequent infections, slow healing and unintended weight loss. Risk factors for developing the disease include being overweight, storing excess fat mainly in the abdominal region, a family history of diabetes, inactivity and being over the age of 45. These last two factors are associated with a drop in lean muscle mass, which some researchers think may play a role.

Type 2 diabetes used to be seen most often in middle-aged adults. Unfortunately, in recent years it has increasingly been seen in young adults, adolescents and even children. If you suspect you have developed the disease, it’s important to see your doctor. Diagnosis is usually via a blood test. Treatment includes weight loss, changes to diet, exercise, blood sugar monitoring and, possibly, the use of medications or insulin.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I’ve heard that when you’re on a diet and you decrease caloric intake by a lot, your body will start to consume muscle for energy. It that really true? How can you lose weight and not wind up losing muscle?

Dear Reader: Discussions about losing weight typically focus on pounds, as in, “I want to lose 10 pounds.” The important follow-up question here is: pounds of what? Work up a sweat with a vigorous set of tennis, and the scale will show you’ve immediately dropped a few pounds -- of water weight. You’ll gain it right back with your next beverage. (A quart of water weighs 2 pounds, in case you were curious.)

Diets that involve a drastic calorie cut do lead to weight loss, but participants wind up burning not only fat, but also significant amounts of lean muscle. That’s a bad idea, because we rely on our muscles for both strength and endurance. Muscle tissue also plays an important role in resting metabolic rate.

The answer to the “pounds of what?” weight-loss question is, of course, fat. When we set a weight-loss target, the goal is to lose fat. Or, to view it in more useful terms, we want to achieve a more healthful ratio of lean tissue to fat. Achieving and maintaining a healthful weight has many benefits, including reducing the risk of diabetes, high blood pressure, coronary artery disease, depression and even certain cancers. And, while it’s tempting to try some of the more extreme low-carb and high-fat diets that are now popular, which promise swift and painless weight loss, we believe a moderate approach yields better and more sustainable results.

In order to maximize fat loss and minimize the loss of lean muscle mass, you need a three-pronged approach. This begins with cutting back calories enough that you’re operating at a slight deficit, but not to the point that your body thinks it’s starving. A recent study in the Netherlands followed volunteers on a five-week diet of 500 calories per day, and those on a 12-week plan of 1,250 calories per day. Both groups lost the same amount of weight -- about 19 pounds. However, the crash dieters lost almost three times as much muscle mass as those who followed the more moderate weight-loss plan.

To stay healthy as you lose weight, eat a wide range of fresh foods, with a focus on lean proteins, healthy fats, and fresh fruits and vegetables. Take care to avoid simple carbohydrates and processed foods. You want a diet that, once you’ve reached your goal weight, you can continue to sustain.

Finally, it’s important to incorporate two kinds of exercise into your daily life: cardio and resistance. Cardio helps to burn fat, and resistance maintains and builds the lean muscle mass that you want to conserve. Again, the aim here is a new set of habits that you’re willing and able to maintain even after you’ve reached your goal weight.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: Our 16-year-old daughter wants to become a vegan. Her father and I think that may be a bit extreme, so we’ve compromised, and first she’s going to try being a vegetarian. What’s a good way for a growing teen to safely make the transition?

Dear Reader: We’re both parents ourselves, so we understand your concerns about meeting your daughter’s nutritional needs. A vegan diet, which cuts out all foods derived from living creatures -- including eggs, dairy products, gelatin and honey -- can send you on a steep learning curve. Even the more lenient parameters of a vegetarian diet take care and planning to be healthful and well-balanced.

As with any diet, the goal is to get enough calories, protein, vitamins and minerals from a wide array of fresh and healthful foods. The good news is that vegetarian and vegan diets are quite popular. That means the information and products your daughter needs to be a healthy vegetarian are widely available.

When following a vegetarian diet, your daughter will no longer eat red meat, poultry, fish or other seafood. Vegetarians may choose whether or not to eat eggs and dairy products. (Some, referred to as pescatarians, include fish in their diets.)

Although it can be tempting to dive into the deep end with a new lifestyle choice, we suggest a gradual transition. Instead of eliminating meat, start by adding an array of foods to your daughter’s existing diet. This includes the tofu, tempeh, seitan, beans, legumes, nuts, seeds and whole grains that will become staples of her new way of eating. Once she’s familiar and comfortable with these new foods, she can start eating them instead of the meat-based meal the rest of the family is having. A vegetarian we know made an easy transition by eliminating one category of meat at a time. She started with beef and, every few weeks, stopped eating another type of meat. Within a few months, she had achieved her goal of becoming a vegetarian.

When it comes to nutrition, you want to keep an eye on B12, a vitamin that’s essential to the proper function of the body's nerve and blood cells. B12 also plays a role in the synthesis of DNA, and it helps prevent megaloblastic anemia, which causes weakness and exhaustion. In addition to meat and fish, B12 is found in milk, cheese, eggs and some fortified cereals. Several studies have found that even vegetarians who consume eggs and milk can become deficient in B12, so a supplement may be a good idea.

People who no longer consume meat also have to take care to get adequate calcium, iron, zinc and protein. Protein needs can be satisfied by eating a variety of beans, legumes, nuts, seeds and soy products, as well as eggs and dairy products.

A few good vegetarian cookbooks will be essential tools for coming up with varied and healthful meals and snacks. We also think it would be wise for your daughter to meet with a registered dietitian to learn the nutritional guidelines of her new lifestyle.

(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)