What time you exercise may be more important than the workout itself

The time of day you exercise may determine how effective the workout is.

Dutch researchers found evidence that a late workout may be more effective than an early workout at shrinking fat, reducing the size of early-stage atherosclerotic lesions, and producing healthy gut bacteria.

Using mice, the researchers simulated human dietary and workout patterns – with some mice exercising early, others late, and a control group not at all. After four weeks, researchers found that the mice that worked out early experienced no change in fat mass or early-stage atherosclerotic lesions. However, late-exercise mice reduced fat mass by 19% and the size of early-stage atherosclerotic lesions by as much as 29% compared to sedentary animals.

Similarly, late exercise increased the abundance of gut bacteria producing short-chain fatty acids with proposed anti-inflammatory properties.

The research is important because we’ve been told that exercise can reduce signs of atherosclerosis or at least stop its progression. But the Dutch study suggests that the time of day when you do your exercise may make all the difference.  

Something else interesting in the research is the fact that late training decreased bacterial diversity in the gut, while promoting the enrichment of short-chain fatty acid (SCFA)-producing bacteria that have been associated with changes to atherosclerosis development in mice. The SCFA produced in bacterial fermentation of dietary fiber can inhibit the formation of foam cells and reduce inflammation. 

More study is needed to assess the real impact of gut bacteria on heart health, but this research suggests a connection that’s worth exploring.