Changes to fat and muscle after 24 weeks of exercise in HIV-positive and HIV-negative people

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  • A study measured the impact of exercise on older HIV-positive and HIV-negative people
  • HIV-positive people were more likely to lose belly fat, but less likely to gain muscle mass
  • Researchers suggest more resistance exercise may be helpful for older people with HIV

The initiation of potent combination HIV treatment (ART) usually leads to a significant reduction in the amount of HIV in the blood. Continued good adherence to ART leads to viral suppression that is sustained. This suppression of HIV allows the immune system to effect partial repairs. In the vast majority of ART users, these repairs are sufficient to keep AIDS-related infections at bay. What’s more, scientists project that many ART users will have near-normal life expectancy.

Aging

As HIV-positive people age, like everyone else they can become less active, undergo decreased levels of testosterone (in men) and estrogen (in women) and gradually build up fat in their abdomen and lose muscle mass. This loss of muscle mass can result in reduced strength and diminished ability to be fully physically functional.

Exercise

A team of scientists in the United States conducted a study of moderate- and high-intensity exercise with HIV-positive and HIV-negative volunteers. A previous analysis from this study reported that exercise improved physical functioning.

In their latest analysis of the data, the scientists focused on changes in body composition—fat and muscle—that occurred as a result of 24 weeks of exercise (three times weekly). They found that exercise helped to reduce the total amount of fat in the body in HIV-positive people. In particular, the amount of belly fat decreased. However, the scientists described overall increases in muscle mass among HIV-positive people as “minimal.” They stated that “a greater emphasis on resistance exercise may be needed to more effectively increase muscle [in HIV-positive people].”

Study details

For six months prior to entering the study, all participants were sedentary. The scientists defined sedentary as doing less than 60 minutes per week of physical activity. Also, the HIV-positive participants were taking ART and had an undetectable viral load for the past two years.

Participants were distributed as follows:

  • 27 HIV-positive people
  • 28 HIV-negative people

Participants underwent supervised exercise sessions three times weekly for 24 consecutive weeks. Time spent exercising was gradually increased to 50 minutes per session. At every session, participants engaged in walking briskly on a treadmill and then doing resistance exercises on machines (such as bench press, leg press and lateral pulldown).

During the first 12 weeks, all participants did exercise of a moderate intensity. After this, participants were randomized to the following two interventions:

  • 12 weeks of continued moderate-intensity exercise
  • 12 weeks of high-intensity exercise

Researchers encouraged participants to eat a “healthy diet” but did not provide nutritional guidance.

The average profile of HIV-positive participants upon study entry was as follows:

  • 93% men, 7% women
  • age – participants were between 50 and 70 years old
  • duration of HIV infection – 23 years
  • duration of ART – 17 years
  • CD4+ count – 546 cells/mm3
  • current or prior use of a type of nucleoside analogue called a thymidine analogue (AZT, d4T) – 68%
  • body mass index (BMI) – 27 kg/m2
  • 15% were current smokers
  • 20% used testosterone supplementation
  • nearly 50% used cholesterol-lowering medicines called “statins”

In general, the HIV-negative participants were of similar age and that group had the same proportion of males and statin use. However, HIV-negative men differed from their HIV-positive counterparts in the following ways: They were slightly heavier, had more total body fat and were less likely to use supplemental testosterone.

Participants underwent numerous assessments, including low-dose X-ray scans to determine body composition.

Results

Adherence to exercise regimens was high, approaching 90% in both groups of people.

Body mass index

HIV-positive people had a modest reduction in BMI (about half a point) and HIV-negative people also had a modest reduction in this assessment.

Muscle mass

HIV-positive people either maintained their muscle mass or modestly increased it (by about 0.5 kg), while HIV-negative people had a greater increase (by about 0.8 kg).

Fat

HIV-positive people lost about 2 kg of fat, while HIV-negative people lost 1 kg of fat. HIV-positive people lost 18 cm2 of fat deep within the belly, while HIV-negative people lost 10 cm2 of this type of fat.

Testosterone

Historically, in the time before ART was available, HIV infection was associated with lower-than-normal levels of testosterone, particularly in men. In some cases, persistent loss of muscle was documented. In the current era, with the widespread availability of ART, large studies suggest that testosterone deficiency is less common in HIV-positive men than in the pre-ART era.

Some hormones in the body come in two forms—one form is bound to protein and the other form is not. The latter is called the “free” form of the particular hormone and is the amount that is available for use by the body. As this is the case with testosterone, many doctors request that laboratories measure or calculate the amount of free testosterone in the blood samples of their patients.

In the present study, levels of free testosterone were not significantly different between HIV-positive and HIV-negative men. This was the case after the scientists removed men from the analysis who had been receiving supplemental testosterone.

Testosterone levels peak during the early morning and endocrinologists tend to recommend that blood be drawn in this period for analysis. However, it is not clear if blood was drawn at that time for testosterone measurement in this study.

Good changes

The good news from this study is that exercise done three times weekly in older, mostly male participants can reduce body fat, particularly fat deep within the belly. This reduction occurred regardless of HIV status. If this reduction was sustained, it has the potential to increase cardiovascular and overall health. Although HIV-positive people lost fat, they did not lose muscle mass—it either stabilized or increased modestly.

Muscles

The reason that HIV-positive people did not gain as much muscle as their HIV-negative counterparts in this study is not clear. The scientists suggest that it is plausible that previous exposure to AZT or d4T may have caused a degree of persistent muscle injury that could have affected muscle growth. However, biopsies of muscle tissue were not done in the present study.

ART has a tremendous impact on survival, but it does not correct all the changes brought about by HIV infection. For instance, ART is able to greatly reduce the level of HIV-related inflammation but not to levels seen in healthy HIV-negative people. It is plausible that this inflammation could have partially affected the ability of HIV-positive people to gain muscle mass. HIV-positive people did not have a significant decrease in a commonly used measure of inflammation – levels of high-sensitivity C-reactive protein (hsCRP) in the blood – during the study.

It is also possible that HIV-infected cells released proteins that could have affected the activity, growth and development of muscle cells. Previous research has found muscle injury in some HIV-positive people who were never exposed to nucleoside analogues. This finding suggests that HIV itself may play a role in affecting muscle health.

In the present study, the number of people with HIV was too small to draw meaningful comparisons of the potential effect of different drug combinations on changes in muscle mass.

To overcome what the scientists called a “blunted increase” in muscle growth to exercise, they suggested that older HIV-positive people “may need to place greater emphasis on resistance exercise.”

For the future

Exercise has many health benefits and the present study is a good step forward. However, there is still a need for more studies of this kind in order to better understand the impact of different exercise regimens on HIV-positive people, including women.

––Sean R. Hosein

Resources

Exercise as medicine – TreatmentUpdate 234

Study finds fat goes up, muscle goes down over time – TreatmentUpdate 235

Pilot study finds intense exercise is good for older HIV-positive men – TreatmentUpdate 228

Exercise + statin yields enhanced benefits – TreatmentUpdate 217

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