Dear Doctor: My friends and I are all getting older, and I've noticed that some of them are on statins to lower their cholesterol. My doctor chose a fibrate for me, Lopid (gemfibrozil). What's the difference between statins and fibrates, and what's special about Lopid?

Dear Reader: Statins and fibrates act in fundamentally different ways. Statins, more officially known as HMG-CoA reductase inhibitors, target cholesterol in the bloodstream, most of which comes from the liver, not from foods that we eat. They work by binding to the enzyme HMG-CoA reductase, which the liver needs to form cholesterol.

Statins act in another way as well. Because they make cholesterol levels fall within the liver, the liver then increases production of a substance, or receptor, that takes LDL, the so-called "bad" cholesterol, from the bloodstream and shepherds it back into the liver. There, it is eventually removed via the bile. Because we make more cholesterol at night, statins are given before bedtime.

Fibrates, which include gemfibrozil (Lopid) and fenofibrate, target triglycerides in the bloodstream. They work by decreasing the liver's release of triglycerides and by increasing the production of lipoprotein lipase, which breaks down triglycerides. In addition, fibrates increase the formation of HDL, the so-called "good" cholesterol; they have only minor effects in reducing LDL. Unlike statins, fibrates should be taken before eating.

Statins have undeniably shown benefits in decreasing the risk of both heart attacks and strokes; fibrates seem to have a more narrow benefit. In 2010, a Lancet review analysis of 18 studies involving more than 45,000 patients showed a 13 percent decrease in heart attacks and angina among people who were taking fibrates, but no reduction in stroke risk, no decrease in overall death rates and no decrease in death rates from heart attacks.

A 1987 study published in the New England Journal of Medicine also showed mixed results. It followed more than 4,000 middle-aged men with elevated triglyceride levels for five years. At the start of the study, one group began using gemfibrozil, and the other group began taking a placebo. At the end of the study, the group that took gemfibrozil had a 34 percent decrease in the risk of coronary heart disease, but there was no difference in the death rate.

Overall, statins appear to have greater benefit than fibrates in decreasing the risk of both heart attacks and strokes. That's not to say fibrates aren't the right choice for some people, however. Significant elevation of triglycerides, greater than 400, can cause inflammation of the pancreas, so people with very elevated triglyceride levels would benefit from a fibrate medication. So too might those with elevated triglycerides and normal LDL cholesterols.

Before you suggest combining a statin and a fibrate for added benefit, be aware that the combination can increase the risk of muscle aches and possible muscle breakdown. On occasion, I will prescribe this combination to my patients with very elevated triglycerides, but I monitor them carefully for any signs of muscular problems or breakdown. Also in such cases, I try to lower the statin dose to decrease the chance of muscular symptoms.

In summary, statins and fibrates work by different mechanisms. Statins have greater benefit than fibrates in decreasing heart attacks and strokes. Fibrates, though, may be appropriate for people with elevated triglyceride levels.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My New Year's resolution was to get more exercise and, I hope, lose a few pounds. Walking is an activity I know I can stick with, but I keep hearing that I should aim for 10,000 steps a day. Where does that number come from, and am I wasting my time if I do less?

Dear Reader: In the battle to sit less and move more, you've already nailed the crucial element -- picking an activity that will survive the inevitable day that your New Year's fervor wears off. Walking is a great option -- it's easy, inexpensive and low-impact, and can be done just about anywhere. Best of all, walking has multiple health benefits.

Walking will do more than just help you control your weight. In fact, even if you don't lose any weight at all, you'll still come out ahead. People who are physically active lower their risk of stroke, heart disease, type 2 diabetes, depression and even some cancers. Bottom line -- they live longer.

For optimal health benefits, the Centers for Disease Control and Prevention say we should spend at least 150 minutes per week doing a moderately paced aerobic activity for no less than 10 minutes at a stretch. (Or 75 minutes per week of vigorous physical activity, but that's an answer to a different question.)

Those 150 minutes of moderate activity can absolutely be spent in your chosen method -- walking -- as long as it's at a brisk pace. Three to four miles per hour is about right for most of us. That's fast enough so that your heart gets pumping, yet you're still able to carry on a conversation. Which brings us to the question of distance, and the mystery of the 10,000 steps.

It turns out that this goal dates back to the mid-1960s, when a pedometer sold in Japan was marketed as "manpo-kei," which translates to "10,000 steps meter." More than 50 years later, we're still in thrall to that clever bit of advertising.

But those 10,000 steps -- that's about five miles -- had a toehold in science. A study at the time found that men who burned 2,000 calories per week through exercise measurably lowered their risk of heart disease. Since a five-mile walk uses roughly 300 calories, to burn 2,000 calories per week takes 10,000 steps.

Is 10,000 steps a make-or-break number from the outset? The short answer is no. Any amount of physical activity above and beyond what you're presently doing is beneficial. The main thing is to ease into your new exercise program in a way that's both safe and sustainable.

Begin with a comfortable pace and a reasonable distance. Maybe that's a 10-minute walk around the block or a brisk two miles to work. Challenge yourself to go a bit farther each week. Whether you're taken with the symmetry of 10,000 steps, or prefer the CDC's recommendation of 150 minutes of exercise per week, what matters most is that you get -- and stay -- moving.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I was recently diagnosed with fatty liver. I researched it a bit, and learned that people with this condition can have a pregnant-looking stomach. Although I've been considered slim my whole life, for the last eight or nine years I've looked about six months pregnant. Please tell me how I can reverse this and quit wearing maternity clothes.

Dear Reader: Fatty liver, officially called hepatic steatosis, is the most common liver disorder in Western industrialized countries, with rates increasing over the last 40 years in step with the rates of obesity. In fact, a 2004 population-based study that imaged the livers of 2,287 people in Dallas, Texas, found fatty liver in 34 percent of the population.

So obviously, you're not alone. The issue you're having with fatty liver is shared by a large percentage of Americans. To understand how this happened, and why the rates of diabetes, obesity and fatty liver have increased over the last 40 years, just visit a supermarket. There you'll find aisle after aisle of high-carbohydrate, high-sugar processed foods.

High-sugar foods such as cookies, candies, cakes, ice cream, sodas and juices raise both insulin and triglyceride levels. So do highly refined carbohydrates such as crackers, potato chips, low-fiber breads, rice and pasta. Processed foods often contain large amounts of both sugar and refined carbohydrates. All these foods are easily converted to fat in the body, and when there's too much fat, it starts to build up in the liver. That can cause an inflammatory reaction that leads to scarring.

Most people have no symptoms of fatty liver; only rarely do patients have related fatigue or stomach fullness. Your doctor may want to investigate whether the weight gain in your abdomen is not simply related to increased fat distribution in that area of your body.

You can try to reverse the condition -- and your weight gain -- by reducing the amount of sugars and carbohydrates you consume.

A review of four studies published last year in the Journal of Research in Medical Sciences found that reducing the amount of dietary carbohydrates to 50 percent or less of total calorie intake successfully led to a decrease in liver fat content. In other words, the type of calories -- not just total calories -- that you consume matters.

Other research, specifically a 2004 study published in the journal Digestive Diseases and Sciences, looked at obese patients undergoing bariatric surgery. Researchers found that people whose carbohydrate intake was greater than 54 percent of their total calories were six and a half times more likely to have liver inflammation compared to those for whom carbohydrates made up less than 35 percent of their total calories. What was interesting about this study was that those who ate a high-fat diet had lower rates of inflammation in the liver. This runs counter to the long-held belief that dietary fat causes people to develop more fat in the body and the liver.

To change your diet, start with sugar. By that I mean eliminate high-sugar foods from your diet -- completely. That means no dessert, no sodas, no juices. High-sugar foods are pervasive within our society, and it takes a daily determination to not consume them, especially when they are a normal portion of our American diet. Further, high-sugar foods are both addictive to the brain and the body. But hang in there: Those addictive effects recede within just a few days of stopping sugar.

Also, reduce carbohydrates that are low in fiber. They can create many of the same problems found with high-sugar foods.

And last but not least, start an exercise regimen -- or ramp up the one you have. It will help you work off extra calories, while also helping you control your body's ability to control glucose levels.

By lowering your intake of sugar and carbohydrates and by increasing your amount of exercise, you'll not only decrease the fat deposits in your liver, but also your risk of diabetes and the size of your midsection.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)