Tuesday, January 20, 2009

Low-Carb Diet Burns Liver Fat

A study conducted by scientists has shown that people who consume low-carb diets depend more on the oxidation of fat in the liver for energy than those on a low-calorie diet.

The researchers say that their findings may have implications for treating obesity and related diseases like diabetes, insulin resistance and nonalcoholic fatty liver disease.

Instead of looking at drugs to combat obesity and the diseases that stem from it, maybe optimizing a diet can not only manage and treat these diseases, but also prevent them.

The study was not to determine which diet was more effective for losing weight, but the average weight loss for the low-calorie dieters was about five pounds after two weeks, while the low-carbohydrate dieters lost about nine-and-a-half pounds.

Researchers randomly assigned 14 obese or overweight adults to either a low-carbohydrate or low-calorie diet, and monitored seven lean subjects on a regular diet. They observed that participants on a low-carbohydrate diet produced more glucose from lactate or amino acids than those on a low-calorie diet. Understanding how the liver makes glucose under different conditions may help regulate metabolic disorders with diet.

People on the low-calorie diet get about 40 percent of their glucose from glycogen, which is comes from ingested carbohydrates and is stored in the liver until the body needs it.

The low-carbohydrate dieters only get 20 percent of their glucose from glycogen. Instead of dipping into their reserve of glycogen, such subjects burnt liver fat for energy.

The significance of the findings lies in the fact that the accumulation of excess fat in the liver can result in nonalcoholic fatty liver disease (NAFLD) -- a liver disease which is associated with metabolic disorders like insulin resistance, diabetes and obesity, and can lead to liver inflammation, cirrhosis and liver cancer.

The people on a low-carbohydrate diet have livers that burn excess fat throughout their entire body and the result could help them if they have nonalcoholic fatty liver disease.

Medically speaking nonalcoholic fatty liver disease or nonalcoholic steathhepatitis (NASH) it often called the "silent" liver disease. The major feature in NASH is fat in the liver, along with inflammation and damage. Most people with NASH feel well and are not aware that they have a liver problem. Nevertheless, NASH can be severe and can lead to cirrhosis, in which the liver is permanently damaged and scarred and no longer able to work properly.

NASH affects 2 to 5 percent of Americans. An additional 10 to 20 percent of Americans have fat in their liver, but no inflammation or liver damage, a condition called “fatty liver.” Although having fat in the liver is not normal, by itself it probably causes little harm or permanent damage. If fat is suspected based on blood test results or scans of the liver, this problem is called nonalcoholic fatty liver disease (NAFLD).

Both NASH and NAFLD are becoming more common, possibly because of the greater number of Americans with obesity. In the past 10 years, the rate of obesity has doubled in adults and tripled in children. Obesity also contributes to diabetes and high blood cholesterol, which can further complicate the health of someone with NASH. Diabetes and high blood cholesterol are also becoming more common among Americans.

NASH is usually first suspected in a person who is found to have elevations in liver tests that are included in routine blood test panels, such as alanine aminotransferase (ALT) or aspartate aminotransferase (AST). When further evaluation shows no apparent reason for liver disease (such as medications, viral hepatitis, or excessive use of alcohol) and when x rays or imaging studies of the liver show fat, NASH is suspected. The only means of proving a diagnosis of NASH and separating it from simple fatty liver is a liver biopsy.

For a liver biopsy, a needle is inserted through the skin to remove a small piece of the liver. NASH is diagnosed when examination of the tissue with a microscope shows fat along with inflammation and damage to liver cells. If the tissue shows fat without inflammation and damage, simple fatty liver or NAFLD is diagnosed. An important piece of information learned from the biopsy is whether scar tissue has developed in the liver. Currently, no blood tests or scans can reliably provide this information.

NASH is usually a silent disease with few or no symptoms. Patients generally feel well in the early stages and only begin to have symptoms—such as fatigue, weight loss, and weakness—once the disease is more advanced or cirrhosis develops. The progression of NASH can take years, even decades. The process can stop and, in some cases, reverse on its own without specific therapy. Or NASH can slowly worsen, causing scarring or “fibrosis” to appear and accumulate in the liver.

As fibrosis worsens, cirrhosis develops; the liver becomes seriously scarred, hardened, and unable to function normally. Not every person with NASH develops cirrhosis, but once serious scarring or cirrhosis is present, few treatments can halt the progression. A person with cirrhosis experiences fluid retention, muscle wasting, bleeding from the intestines, and liver failure.

Liver transplantation is the only treatment for advanced cirrhosis with liver failure, and transplantation is increasingly performed in people with NASH. NASH ranks as one of the major causes of cirrhosis in America, behind hepatitis C and alcoholic liver disease.

Though NASH has become more common, its underlying cause is still not clear. It most often occurs in persons who are middle-aged and overweight or obese. Many patients with NASH have elevated blood lipids, such as cholesterol and triglycerides, and many have diabetes or pre-diabetes, but not every obese person or every patient with diabetes has NASH.

Furthermore, some patients with NASH are not obese, do not have diabetes, and have normal blood cholesterol and lipids. NASH can occur without any apparent risk factor and can even occur in children. Thus, NASH is not simply obesity that affects the liver.

While the underlying reason for the liver injury that causes NASH is not known, several factors are possible candidates:

insulin resistance
release of toxic inflammatory proteins by fat cells (cytokines)
oxidative stress (deterioration of cells) inside liver cells

Currently, no specific therapies for NASH exist. The most important recommendations given to persons with this disease are to reduce their weight (if obese or overweight), follow a balanced and healthy diet, increase physical activity, avoid alcohol and avoid unnecessary medications.
These are standard recommendations, but they can make a difference. They are also helpful for other conditions, such as heart disease, diabetes, and high cholesterol.

A major attempt should be made to lower body weight into the healthy range. Weight loss can improve liver tests in patients with NASH and may reverse the disease to some extent. Research at present is focusing on how much weight loss improves the liver in patients with NASH and whether this improvement lasts over a period of time.

People with NASH often have other medical conditions, such as diabetes, high blood pressure, or elevated cholesterol. These conditions should be treated with medication and adequately controlled; having NASH or elevated liver enzymes should not lead people to avoid treating these other condition.