MONDAY, August 11, 2008 (Health.com) — Is it possible to be fat and healthy? Two major new studies published this week in Archives of Internal Medicine suggest the answer is "maybe," depending on where the fat lurks in your body. In normal and overweight people, those with belly fat are at greater risk of heart disease and diabetes than those with extra padding in the buttocks or thighs.
But for the obese, the ultra-high-risk spot may be fat accumulation in the liver.
Not all excess fat is created equal
In one study, researchers at the University of Tübingen, Germany, divided 314 patients into four groups: normal weight, overweight, obese but still sensitive to insulin, and obese with insulin resistance. They found that not all the obese patients had the same health profiles. Some had clogged arteries, which is a heart attack risk factor, and were insulin-resistant, a precursor to diabetes in which the body loses its sensitivity to the blood-sugar-regulating hormone.
But about 25% of the obese people had clear arteries and no insulin resistance—indeed, these people looked no different than normal-weight participant in those terms.
“No one would say overweight is healthy,” says Lewis Landsberg, MD, of the Northwestern University Comprehensive Center on Obesity in Chicago. “The message is that being overweight is much more unhealthy for some people than others.”
How humans are like force-fed geese
The big difference between obese patients and their healthier peers seemed to be the percentage of fat in the liver. Obese people who were insulin-resistant more than roughly double the amount of fat in their liver as obese people who were not (8.8% vs. 3.5%, respectively).
In comparison, normal weight and overweight people had a liver-fat level of about 1.9% and 3.8%, respectively.
The infiltration of the liver by fat is increasingly being recognized as one of the potential dangers of too much weight, says Judith Wylie-Rosett, who holds a doctorate in education and is professor and head of behavioral and nutritional research at the Albert Einstein College of Medicine in New York.
Just like force-fed geese develop fatty livers that are used to make foie gras, excess calories may lead to fat infiltration of the human liver, says Wylie-Rosett, who is a coauthor of the second study in the journal.
“We don’t yet know what the longer term risks are [of excess fat in the liver], but we assume that it may then lead to scarring, and what we are now talking about is nonalcoholic liver disease,” says Wylie-Rosett. “It’s an area of tremendous concern particularly as younger people are becoming heavier and heavier and appear to be getting some of these fatty infiltrations in the liver.”
In the second study, Rachel Wildman, PhD; Wylie-Rosett; and other colleagues analyzed U.S. survey data from 5,440 people. They found a cluster of high-risk symptoms—elevated blood pressure, triglycerides, and blood glucose, among other problems—in 24% of normal-weight people, 49% of the overweight, and 68% of the obese.
“Just because you are lean it doesn’t mean you don’t have cardiometabolic risk,” she says. “We’ve tended to think that weight is a proxy for health but it may be more complicated than that. If you are obese there are still things you can do to be healthy and we need to think about where you stand on the cardiometabolic risk continuum.“
How can you tell if you’re at risk?
• Do you have an apple- or pear-shaped body? Many studies have suggested that excess weight around your gut is more dangerous than weight around the hips and thighs. Belly fat pads organs, and can increase your risk of diabetes compared to other types of fat.
• What is your age and ethnicity? In studies, the odds of being in a high-risk category increased with age, regardless of body size. And in obese people, African Americans were at a lower risk of having metabolic risk factors than white people of the same age and body size.
• Check your lifestyle. People who don’t smoke and who exercise, even if they are obese, are less likely to be in the high-risk category. Smoking seems to encourage fat to cluster in the gut area, says Wylie-Rosett, and exercise protects you, regardless of body size.
• Visit your doctor. Dr. Landsberg says most doctors will check your body mass index, a measure of weight and height, but abdominal circumference is an important indicator of risk too. You won’t be getting a liver scan for fat content anytime soon (too pricey and of uncertain value), but doctors sometimes check for elevated liver enzymes, a sign of liver function. Standard tests for high blood pressure, lipid levels, and increasingly, blood glucose, will help determine if you’re at risk for heart disease and diabetes, regardless of weight.
Next page: What you should do about it
If tests suggest you are at high risk for heart disease or diabetes, the main thing to do is lose weight, says Dr. Landsberg.
“All physicians would recommend for a number of reasons that overweight patients should lose weight; there’s cardiovascular disease risk, there’s cancer risk, which wasn’t addressed in these studies,” he says. “So weight loss is important.”
However, if you’re overweight and can’t seem to shed the pounds, you should also keep trying, because exercise can help, says Wylie-Rosett.
“The physical activity story is—don’t just look at the scale, look at your whole lifestyle,” she says. “If you’re physically active, you still are potentially a lot healthier even if your weight doesn’t change much.”