Exercise resulted in greater reduction in visceral adipose tissue (VAT) relative to weight loss than did pharmacological interventions, found a US meta-analysis.
Researchers at University of Texas Southwestern Medical Centre analysed two types of interventions – lifestyle modification (exercise) and pharmacological (medicine) – to learn how best to defeat fat lying deep in the belly.
"Visceral fat can affect local organs or the entire body system. Systemically it can affect your heart and liver, as well as abdominal organs," said senior author and cardiologist Dr Ian J Neeland, assistant professor of internal medicine. "When studies use weight or body mass index as a metric, we don't know if the interventions are reducing fat everywhere in the body, or just near the surface."
To find out, the researchers evaluated changes in visceral fat in 3,602 participants over a 6-month period measured by a CT or MRI exam. Both exercise and medicines resulted in less visceral fat, but the reductions were more significant per pound of body weight lost with exercise.
"The location and type of fat is important. If you just measure weight or BMI, you can underestimate the benefit to your health of losing weight," said Neeland, a Dedman family scholar in clinical care. "Exercise can actually melt visceral fat."
Participants in exercise trials were 65% female, with a mean age of 54 and mean BMI at enrolment of 31. Exercise regimens were monitored, not self-reported. The majority of exercise trials were performed in the US and Canada, while pharmacologic trials included the US, Canada, Sweden, Japan, and four multinational cohorts.
The medications used by study participants were US Food and Drug Administration (FDA) approved or in the FDA approval pipeline.
According to the US Centres for Disease Control and Prevention, obesity affects nearly 40% of adult Americans. Neeland said researchers previously thought of fat as inert storage, but over the years this view evolved and fat is now seen as an active organ.
"Some people who are obese get heart disease, diabetes, or metabolic syndrome – and others don't," Neeland said. "Our study suggests that a combination of approaches can help lower visceral fat and potentially prevent these diseases."
Objective: To assess the effectiveness of exercise and pharmacotherapy interventions in reducing visceral adipose tissue (VAT).
Patients and Methods: A systematic search of Ovid MEDLINE, Scopus, Web of Science, Cochrane Library, ClinicalTrials.gov, New York Academy of Science Grey Literature Report, and OpenGrey was combined with hand searches of existing literature. A total of 2515 titles and abstracts were reviewed. Only randomized controlled trials evaluating the effectiveness of monitored exercise or pharmacological interventions in reducing VAT by using computed tomography or magnetic resonance imaging during a sustained intervention period (≥6 months) were included. Data were independently extracted by reviewers according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and assessed for quality and risk of bias. Separate analyses for each intervention were performed using random effect models, with pooled estimates of the change in VAT area (in centimeters squared) from baseline to follow-up reported as standardized mean difference (SMD; with 95% CI).
Results: A total of 3602 participants from 17 randomized controlled trials were included in the final analysis. Both exercise and pharmacological interventions were associated with significant reductions in VAT: small reduction with pharmacological interventions (SMD, −0.27; 95% CI, −0.47 to −0.07; P=.02) and more substantial reductions with exercise interventions (SMD, −0.54; 95% CI, −0.63 to −0.46; P<.001). The mean absolute VAT reduction was greater in pharmacological trials than in exercise trials. Meta-regression exhibited a linear correlation between VAT and weight loss (R2=0.52 for exercise and R2=0.88 for pharmacological interventions), but VAT reduction relative to weight loss differed by intervention type.
Conclusion: Exercise interventions resulted in greater reduction in VAT relative to weight loss than did pharmacological interventions. A preferential reduction in VAT may be clinically meaningful when monitoring success of interventions because weight loss alone may underestimate benefits.
AuthorsShreya Rao, Ambarish Pandey, Sushil Garg, Bryan Park, Helen Mayo, Jean-Pierre Després, Dharam Kumbhani, James A de Lemos, Ian J NeelandUT Southwestern Medical Centre material Mayo Clinic Proceedings abstract