Exercise has superior dose-dependent effect on visceral fat vs. caloric restriction

Both exercise and caloric restriction reduced visceral adipose tissue among adults with overweight and obesity, but only exercise had a dose-dependent effect, according to researchers.

Francesco Recchia, a PhD student at the University of Hong Kong, and colleagues conducted a systematic review and meta-analysis of randomized control trials to better understand the dose-response effects of caloric restriction and exercise on visceral adipose tissue in adults with overweight and obesity.

“Exercise and caloric restriction can both stimulate weight loss via a negative energy balance, which is achieved through an increased energy expenditure or a decreased caloric intake, respectively,” the researchers wrote in the British Journal of Sports Medicine.

Study coauthor Parco M. Siu, PhD, FRSB, FACSM, FECSS, FHKASMSS, an associate professor and head of the division of kinesiology at the University of Hong Kong’s School of Public Health, told Healio that “visceral fat is a strong indicator of cardiometabolic health and overall mortality.”

“It is, therefore, crucial that adequate strategies are implemented to reduce the prevalence of metabolic disorders such as obesity worldwide,” Siu said. “Our findings support the use of exercise as an effective lifestyle strategy to reduce visceral fat in overweight or obese people. Exercise might therefore be used for the prevention and treatment of disorders that are caused by an accumulation of visceral fat.”

The researchers searched CINAHL, Embase, PubMed and Web of Science for randomized controlled trials that compared caloric restriction or exercise against eucaloric controls among adults with overweight or obesity, and ultimately included 40 trials with 2,190 participants. Primarily looking for the change in visceral fat measured by CT or MRI, the researchers performed meta-analyses and meta-regressions to estimate the overall effect size (ES) and dose-dependent associations between caloric restriction and exercise on visceral fat.

Recchia, Siu and colleagues found that, overall, caloric restriction (ES = 0.53) and exercise (ES = 0.28) reduced visceral fat compared with the controls.

Additionally, exercise alone demonstrated a dose-response effect of 0.15 (P < .001) per a deficit of 1,000 calories per week. There was no dose-dependent effect associated with caloric restriction. However, this may be due to “the limited number of studies that were available for analysis, compared with exercise studies,” according to the researchers, and "more evidence is warranted to elucidate the comparative effectiveness and the dose-dependent responses of these two lifestyle interventions.”

“Our findings suggest that, in the presence of an energy deficit, both exercise and caloric restriction can effectively reduce visceral fat,” Siu said. “However, only exercise showed a dose-dependent relationship. This means that the more we exercise during the week, the greater the amounts of visceral fat that we can lose. The same relationship was not observed for caloric restriction studies, meaning that there might be a limit to the benefits of diets on our body’s ability to burn fat.”

The secondary outcome the researchers analyzed was waist circumference.

“Our results showed a dose-dependent effect for waist circumference in both exercise and caloric restriction interventions,” they wrote. “These findings are promising, although they contrast with the primary outcome analyses, as visceral fat is strongly correlated with waist circumference, but our primary outcome analyses did not reveal a dose-response effect of caloric restriction on visceral fat.”

Recchia, Siu and colleagues also noted that the associations of visceral fat with measurements like waist circumference and BMI “varies greatly among individuals in different age and sex groups.”

“Therefore, it is not surprising that the large cohort analyzed in this study showed differential responses to visceral fat and waist circumference outcomes,” they wrote. “Taken together, our results support the dose–response effects of both exercise and caloric restriction strategies in reducing waist circumference in overweight and obese adults.”

Siu said the findings “strengthen the role of exercise for the management of visceral fat in people with overweight or obesity.”

“Primary care providers should consider the prescription of lifestyle modification programs including an increase in physical activity levels for treating people with unhealthy amounts of visceral fat,” Siu said. “Over the past decade, more and more research has emphasized the impact that exercise has on our health. Exercise was shown to prevent/improve symptoms of countless somatic and psychiatric conditions, such as cancer, diabetes, depression and insomnia. With this research, we intend to contribute to the promotion of exercise as a potential lifestyle treatment strategy for the management of metabolic disorders like obesity.”

The researchers also noted that their findings align with a consensus statement recently published by the International Atherosclerosis Society and the International Chair on Cardiometabolic Risk Working Group on Visceral Obesity. The consensus statement “described a plausible relationship between reductions in visceral fat and waist circumference but concluded that a precise estimation of visceral fat from waist circumference is not possible.”

“Our results suggest that exercise might be more suitable than caloric restriction for visceral fat loss in overweight and obese individuals,” Recchia, Siu and colleagues wrote. Though, “differential metabolic adaptations and individual variations are potential causes for the difference in treatment responses to the two interventions.”