Chicago, IL - In a finding that shifts the spotlight away from body weight and focuses instead on body fat distribution, new research shows that metabolic syndrome in older men and women is associated with excess accumulation of visceral abdominal or intramuscular fat, even in normal-weight individuals.

Indeed, write Dr Bret H Goodpaster and colleagues in the April 11, 2005 issue of the Archives of Internal Medicine, the associations between metabolic syndrome and these particular types of regional fat deposits were strongest in people whose weight was normal.[1]

"If you're an older person and you're of normal weight, that still doesn't get you off the hook and you should ask your physician about waist circumference," Goodpaster told heartwire. "For physicians, don't assume just because someone is at normal body weight that they're not at risk for type 2 diabetes or metabolic syndrome."

Goodpaster et al's study is not the first to find associations between visceral and subcutaneous adiposity and metabolic syndrome, but, as he points out, the study is one of the first to look specifically at older adults in a large, community-dwelling population.

If you're an older person and you're of normal weight, that still doesn't get you off the hook.

Their study examined 3035 adults aged 70 to 79, of whom almost 42% were black. Prevalence of metabolic syndrome was 39% in the entire cohort and highest in obese men and women. As well, overweight participants were more likely than normal-weight participants to have metabolic syndrome. However, body fat per se did not seem to account for the increased risk, since differences in total body fat between people with and without metabolic syndrome were modest in normal-weight and overweight men and not different at all in women. Across all weight categories, people with metabolic syndrome actually tended to have higher lean body mass than those without metabolic syndrome.

Across the study, regional fat distribution was more important than weight. Using computed tomography (CT) to assess fat distribution, Goodpaster et al found that visceral adipose tissue was nearly 50% higher in men and women with metabolic syndrome. The association between higher visceral fat and metabolic syndrome was particularly noticeable in normal-weight and overweight men and women, but less so in the obese. Higher subcutaneous adipose tissue as well as higher intermuscular adipose tissue was significantly associated with metabolic syndrome in normal-weight and overweight, but not in obese, men, and not in women.

"Regional fat distribution, particularly visceral abdominal adipose tissue and intermuscular fat, clearly discriminated those with the metabolic syndrome, particularly among the nonobese," the authors write. "This implies that older men and women can have normal body weight and even have relatively lower total body fat but still have metabolic syndrome, due to the amount of adipose tissue located intra-abdominally or interspersed within the musculature."

"We're not saying that obesity itself is not a strong risk factor for the development of metabolic syndrome; that's not true," Goodpaster explains. "But what we do see is that these relationships with the regional fat distribution are stronger in the normal-weight individuals, and if physicians are not measuring the fat in these particular areas, they're going to miss whether or not the patient is at risk of metabolic syndrome."

While most doctors' offices do not have CT scanners, Goodpaster points out that measuring waist circumference has been shown to be a good surrogate means of estimating visceral fat. In terms of practical advice for patients, Goodpaster notes that other studies have indicated that visceral adipose tissue is very responsive to exercise and calorie restriction.

Of note, subcutaneous fat in the thighs of obese men and women was associated with a lower prevalence of metabolic syndrome, a finding that supports earlier findings that the "apple"-shaped physique is linked more closely to cardiovascular and diabetes risk than the "pear."

Another key observation, say the authors, is that prevalence of metabolic syndrome appears to be similar between races. Where differences emerge are in the specific criteria by which participants met the diagnosis of metabolic syndrome. Blacks had higher rates of hypertension and abnormal glucose metabolism, whereas whites were more likely to have poor lipid profiles.

"Clearly when you look at the individual components that make up the syndrome, there are definitely race differences," Goodpaster told heartwire. "Whether or not we're at the point of treating the syndrome as a whole is the question. And I think that the evidence from this paper would suggest that we're not there and that we do need to treat these components individually."