Changes in weight are associated with different factors depending on whether a person is taking HAART or not, according to the latest findings of the US Nutrition for Healthy Living Study. For patients not on HAART, fluctuations in viral load are associated with weight changes; but for those on successful and stable HAART, it is changes in CD4 cell counts and not viral load that are associated with changes in weight. The study is reported in the January 1st issue of Clinical Infectious Diseases.
Weight loss and wasting still occurs in up to one third of HIV-positive patients in the developed world. Although a link between viral load and weight loss has already been defined, less is known about how HAART influences this relationship. Consequently, researchers overseeing the ongoing, cohort-based Nutrition for Healthy Living Study in Boston and Providence, New England, examined weight and HAART use in order to improve understanding of changes in body weight during the HAART era.
A total of 318 out of the 714 study participants were eligible for this analysis. All participants were adults, with any stage of HIV infection, taking or not taking HAART. Analysis was restricted to those who had study visit intervals between four and nine months, for whom there was complete data on viral load, resting energy expenditure (REE), and HAART use. As a consequence, fewer women, non-whites, heterosexuals and injecting drug users were included in the analysis compared with the cohort as a whole.
The 318 participants included 19% women, 36% non-whites, 31% of individuals likely infected through heterosexual HIV transmission and 22% injecting drug users. At the time of enrolment, mean body mass index (BMI) was significantly higher (25.5 vs. 24.4; p=.02) among HAART users compared with non-HAART users.
In univariate analysis, each log10 increase in viral load was significantly associated with weight loss of 0.34kg across the same interval (p=.001). On average, participants who had started HAART between study visits gained weight, and those who stopped HAART between study visits lost weight.
Multivariate analysis examining viral load, CD4 count, REE, total energy intake and HAART use on both weight and BMI were performed; although only results on weight are reported here, the authors note that changes in BMI were similar. The only two highly statistically significant factors for weight change were:
- increasing daily REE (0.31 kg per kcal/kg of body weight; p<.001>
- decreasing CD4 cell count (0.33 kg per 100 CD4 cells; p<.001>
Separate analyses regarding the relationship between HAART use and changes in body weight found the following:
no HAART
- a 1 log10 increase in viral load was significantly associated with a weight decrease of 0.92kg (p=.003)
- a 1 unit increase in daily REE per kg of body weight was significantly associated with 0.38kg decrease in weight (p<.001>
on HAART
- a change in viral load was not associated with a change in body weight (p=.66)
- a CD4 cell count decrease of 100 cells/mm3 was significantly associated with 0.35kg decrease in weight (p<.001>
- a 1 unit increase in daily REE per kg of body weight was significantly associated with 0.26 kg decrease in weight (p<.001>
The unexpected association of CD4 count changes on weight in people on HAART suggests that controlling viral load is not enough to affect weight changes. One question not directly answered by the study is whether individuals on HAART, but with detectable viral loads, would gain weight if their HAART regimen were changed and their viral loads become undetectable. The authors suggest this could be the case, however, and suggests that individuals who make “changes in adherence or changes in the HAART regimen are likely to gain weight.”
However, eating more will not, in itself, counteract weight loss. The authors comment that, “for the average patient taking HAART” and still experiencing weight loss, “our data suggest that an increase in energy intake is not likely to increase weight.”
The authors conclude that the association of resting energy expenditure (REE) with weight, regardless of CD4 and viral load changes, on or off HAART, calls into question the previous assumption that viral load affect REE and “suggests that additional independent mechanisms may exist...Further research is needed to understand the strong, independent effect of REE and changes in REE on weight change.”
Myaka Mwamburi D et al. Understanding the role of HIV load in determining weight change in the era of Highly Active Antiretroviral Therapy. CID 40, 167-73, 2005.