Cutting sedentary time improves cardiometabolic outcomes

Reducing sedentary behaviour (SB) by about an hour – without intentionally incorporating exercise or any moderate-to-vigorous physical activity (MVPA) into a daily regimen – improved cardiometabolic outcomes in adults with metabolic syndrome (MetS), a Finnish study suggests.

Physical inactivity carries the risk of developing chronic diseases. [Lancet 2012;380:219-229; Circulation 2020;141:1113-1115] “As a major proportion of adults globally are insufficiently physically active, reducing SB instead of increasing PA may be a more feasible method for achieving health benefits,” said the researchers.

The effects of a 3-month free-living intervention on cardiometabolic outcomes were evaluated in 64 sedentary middle-aged adults with MetS (mean age 58 years, 58 percent female). More than half were obese (59 percent) while the rest were overweight. They were randomized 1:1 to either the intervention or the control arm. Participants in the intervention arm were to limit SB by an hour daily by increasing standing and LPA* without necessarily engaging in exercise or MVPA. Those in the control arm were instructed to carry on with their usual habits. [J Sci Med Sport 2022;25:579-585]

“[Our study showed that] reducing daily SB by 50 minutes and increasing LPA and MVPA [by 19 and 24 minutes daily, respectively] resulted in beneficial effects in several cardiometabolic risk markers in adults with MetS in 3 months,” said the researchers.

The significantly improved markers were fasting insulin (83.4 vs 102 pmol/L; p=0.01), insulin resistance (HOMA-IR**; 3.2 vs 4.0; p=0.01), HbA_1c (37 vs 38 mmol/mol; p=0.03), and ALT*** (28 vs 33 U/L; p=0.008). Of note as well were the near-significant effects on AST*** (28 vs 30 U/L; p=0.06) and GGT*** (29 vs 31 U/L; p=0.07).

Diabetes, liver benefits

Given the improvements in glucose metabolism and diabetes risk markers, it appears that sitting less could be beneficial particularly from a diabetes-prevention perspective. “[Hence,] sitting less may be an additional approach to aid in the prevention of cardiometabolic diseases in risk populations,” said the researchers.

“[The findings] may have an important impact on public health and disease prevention in risk populations if benefits in several diabetes risk markers can be achieved with SB reductions,” they continued.

The effect of the intervention on ALT is a novel finding, the researchers noted. “[The liver] enzymes are markers of liver dysfunction or injury and are most often elevated due to non-alcoholic fatty liver disease, which is considered the hepatic expression of MetS.”

More movement still recommended

The researchers stressed that the effects in the intervention arm primarily occurred “due to increases in the control arm that exceeded any changes in the intervention arm.” Also, the increases in the control arm occurred despite a significant increase in daily steps (~2,000 steps). “[While this could be a statistical phenomenon or seasonal/spontaneous variation, this implies] that the biomarker levels in adults with MetS rise steadily over time as MetS precedes the development of cardiometabolic diseases.”

“[As such,] SB reduction alone without exercise/PA component might not be enough to prevent this. It seems that in a highly sedentary and inactive risk population, a substantial increase in volume and intensity of PA might be needed to improve [cardiometabolic] risk markers,” they continued.

Incorporating structured exercises may be a way to pull physically inactive individuals out of the SB pit to achieve subsequent health benefits.

However, the sample size was small and dietary intake was not evaluated. The sustainability of the effects was also not reported given the lack of follow-up data. The findings were also limited to sedentary middle-aged adults with MetS. Nonetheless, these might still be applicable to wider populations given the global prevalence of obesity and physically inactive lifestyles, the researchers said.