Lipodystrophy-related differences in waist size not seen in HIV-positive men

Measuring body changes

Lipodystrophy – the blanket term for HIV-associated changes in body fat distribution – can be measured in several ways, all of which have pros and cons. Dual X-ray absorptiometry (DEXA), computerised tomography (CT), and magnetic resonance imaging (MRI) scans are the most accurate methods, but are expensive and troublesome to use.

This study, by researchers at Johns Hopkins University and several other American medical centres, used ‘anthropometry’ – simple ‘tape measurements’ of waist, hip, and limb circumference (size as measured around). While lacking the sophistication of DEXA, CT and MRI, anthropometric measurements can provide quick, simple information without the need for expensive equipment.

In a study published in the November 1^st edition of the Journal of Acquired Immune Deficiency Syndromes, a study team took body measurements of HIV-positive and HIV-negative men and compared the changes in those measurements over a four-year time span. Predictably, waist and hip sizes increased as the men aged. However, while HIV-positive men on potent anti-HIV therapy had slower increases in hip size, changes in waist size over time were the same regardless of drug treatment or HIV status. This confirms several earlier study findings, and suggests that waist-to-hip ratio - a quick and easy measurement - may have an important place in lipodystrophy monitoring.

Previous lipodystrophy research

Several factors make lipodystrophy research difficult: there is not yet a single, universal definition of ‘lipodystrophy’; people with HIV have a wide variety of treatment histories; treatments themselves change with time; and people’s bodies naturally change shape with age.

Several studies in the past few years have shown that fat loss in the face and extremities (‘lipoatrophy’) and fat gain in the trunk and belly (‘lipohypertrophy’) are separate processes. Beyond that, many things are less certain. One study has shown that, after starting antiretroviral treatment, HIV-positive men tend to lose limb fat, but not gain central fat. However, this was not compared to HIV-negative men. Studies in women have been inconsistent, some showing greater waist sizes in HIV-positive women, others showing limb fat loss but not central fat buildup to be more common in HIV-positive women.

These results tend to contradict earlier observations – that antiretroviral treatment sometimes causes dramatic increases in belly size. Belly size increases also continue to be a ‘real world’ observation seen by many people with HIV, and anecdotally by many doctors. The contradictions between ‘common sense’ and detailed study observations have not yet been explained; in fact, this newly published study supports the observations that HIV-positive men do not, in fact, tend to gain belly fat.

The MACS study

The latest study looked at groups of men enrolled in the long-running US Multicenter AIDS Cohort Study (MACS). This large study enrolled thousands of men from four large US cities between 1983 and 1991: 1,053 of these participants, most recently seen in 2003, were included in this body-composition study. Relatively small numbers were HIV-positive but not on antiretroviral therapy (94) or on one- or two-drug therapy (79); 488 were on potent HIV therapy (3-drug therapy or more), and 392 were HIV-negative.

On average, hip and waist sizes increased in all of the men over the four-year study period, regardless of HIV status or antiretroviral use. The researchers then looked at the rate of change of hip and waist sizes – how quickly or slowly the increases occurred. They found that waist size increased at a similar rate in all the men. However, hip size increased more slowly in men on potent than in HIV-negative men, creating a corresponding difference in the waist/hip ratios. (In HIV-negative people, waist size measurement and waist/hip ratio - waist size divided by hip size - can help predict the risk of cardiovascular disease and diabetes. Thicker waists and higher waist/hip ratios indicate higher risk levels.)

Annual changes in waist size ranged between about 0.25cm and 1.25cm, with so much overlap between the different groups that there was no significant difference overall. Hip size increased very little in the men on HAART – an average of only about 0.2cm. Hip size increases were greater in those on fewer or no drugs, or HIV-negative – upwards of 0.5cm per year.

The researchers concluded that “on average, increases in abdominal girth are not quantitatively different in HIV-infected men compared with HIV-seronegative controls”, and that “the more rapid changes in waist/hip ratios observed among HIV-infected patients receiving HAART were attributable to differences in rates of change in hip circumference.” They believe that the waist/hip ratio may be a useful tool, as it is “a powerful predictor of insulin sensitivity among HIV-infected patients,” and “a significant predictor of lipodystrophy, independent of body fat measurements assessed by [other means].”