Evidence summary
Within overweight and obese individuals, individuals with low levels of visceral adipose tissues (VATs) are seen as having lower cardiovascular disease risk profile. Higher levels of visceral fat, including intrahepatic fat, may also exist in less overweight individuals and signify a “silent” risk for cardiovascular diseases[1].
3 meta-analyses were identified that investigated the effect of physical activity on visceral adiposity in subjects that were overweight or obese. Visceral fat was measured using CT in most cases [2,3,4].
In a meta-analyses by Lee et al, five trials reported the effects of the exercise interventions on visceral fat vs control (no exercise intervention). The exercise interventions were effective in reducing visceral fat (d = −1.08 (95% CI, −1.60–−0.57; p < 0.001))[2], where d =effect size. The average exercise intervention necessary to elicit beneficial effects was of moderate to vigorous intensity, 50 min a day, 4 times per week, and of aerobic type.(2)
A meta-analysis by Rao et al focused on 2094 older individuals (mean age of 54) and found that 12 trials with exercise intervention showed a medium reduction in VAT (standardized mean difference [SMD] −0.54, 95% confidence interval [CI] −0.63, −0.46)[3] Among the exercise trials, aerobic regimens reduced VAT the most, producing an absolute reduction of 16.4 cm2 (SD = 37.8), followed by combined aerobic/resistance regimens (14.0 cm2, SD = 23.6) and resistance-only regimens (12.2 cm2, SD = 46.5).
Smart et al looked at intrahepatic fat in 1530 individuals and found that exercise intervention studies with total exercise programme workload >10 000 kcal produced significant improvements in intrahepatic fat, −3.46% (95% CI −5.20% to −1.73%), p<0.0001, I2=73%; effect size (standardised mean difference, SMD) −1.77 (−3.11 to −0.42), p=0.01, I2=77% [4].
Even a walking exercise programme and a daily step goal of 12000 steps per day may lead to some reduction in VAT, even if no weight loss is seen, as found in a randomised controlled trial by Chiang et al[5].
Quality of evidence
A: Consistent evidence from meta-analysis and systematic review
Strength of recommendation
1: Moderate benefit, low risk of physical activity
Conclusion
Exercise interventions, particularly aerobic exercise, result in a reduction in visceral adiposity in patients who are overweight or obese. Organ fat may be reduced in patients even though they notice no change to their outward appearance.
References
1. Powell-Wiley TM, Poirier P, Burke LE, Després J-P, Gordon-Larsen P, Lavie CJ, et al. Obesity and Cardiovascular Disease: A Scientific Statement From the American Heart Association. Circulation. 2021 May;143(21):e984–1010.
2. Lee HS, Lee J. Effects of Exercise Interventions on Weight, Body Mass Index, Lean Body Mass and Accumulated Visceral Fat in Overweight and Obese Individuals: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Int J Environ Res Public Health. 2021 Mar;18(5).
3. Rao S, Pandey A, Garg S, Park B, Mayo H, Després J-P, et al. Effect of Exercise and Pharmacological Interventions on Visceral Adiposity: A Systematic Review and Meta-analysis of Long-term Randomized Controlled Trials. Mayo Clin Proc. 2019 Feb;94(2):211–24.
4. Smart NA, King N, McFarlane JR, Graham PL, Dieberg G. Effect of exercise training on liver function in adults who are overweight or exhibit fatty liver disease: a systematic review and meta-analysis. Br J Sports Med. 2018 Jul;52(13):834–43.
5. Chiang T-L, Chen C, Hsu C-H, Lin Y-C, Wu H-J. Is the goal of 12,000 steps per day sufficient for improving body composition and metabolic syndrome? The necessity of combining exercise intensity: a randomized controlled trial. BMC Public Health [Internet]. 2019;19(1):1215. Available from: https://doi.org/10.1186/s12889-019-7554-y