Sedentary behavior leads to our bodies resisting the usual post-meal response improvements from exercise. This condition has been termed ‘exercise resistance’. Read on, because this article might be about you.
A recent landmark research study (Akins et al., 2019; Kim et al., 2016) has found that sedentary behavior such as sitting can cause our bodies to resist certain positive effects of exercise. This study examined how our bodies respond to meals, and found that people who engaged in prolonged sedentary behavior such as sitting develop ‘exercise resistance’, meaning their bodies do not show the same positive effects to exercise as those who are less sedentary. That comes with severe consequences, as we shall see.
How our bodies respond to meals
After we eat a meal, our bodies process the nutrients. When they respond well, the fat and sugar in our food are broken down for energy and maintain vital functions. When they respond poorly, this fat and sugar can instead circulate in our blood, ultimately lead to inflammation, disturbed hormonal balance and in the long run clog our arteries. The process of chronic inflammation and accumulation of fat cells in our arteries is known as atherosclerosis, and this alarming condition is a strong risk factor for cardiovascular disease, the leading cause of death worldwide as well as stroke, kidney disease and dementia.
The solution to level these negative post-meal responses has long been exercise. Even normal walking, performed after meals has been shown to decrease the levels of sugar in the blood by nearly 50% (Manohar et al., 2012) by improving how well the body breaks down the sugar from the meal. We can say, the better your body is adapted to metabolize sugar and fat following a meal, the lower your risk for diabetes, atherosclerosis and cardiovascular disease.
Why one bout of exercise is not enough
However, this latest study (Akins et al., 2019) shows that individuals who engaged in sedentary behavior (<4000 steps/day) for an extended period of time (4 days) before completing a vigorous hour of exercise did not see the desired metabolic responses following a meal. Usually, exercise would improve the conversion of fat cells to energy, instead of those fat cells clogging up arteries. However, as the researchers state:
“It seems that something inherent to inactivity and/or prolonged sitting makes the body resistant to the 1 hour of exercise preventing the normally derived metabolic improvements following exercise."
While the molecular mechanisms behind exercise resistance are not yet fully understood, this finding demonstrates that sedentary behavior leads to our bodies resisting the usual improvements from exercise. Specifically, there was no improved response seen for post-meal responses to triglyceride fat cells, glucose sugar, or insulin. One theory from the researchers is that prolonged sitting affects several important cellular metabolic mechanisms that occur following meals. In particular, the researchers suggest that prolonged sitting may reduce lipoprotein lipase (LPL), an enzyme located within the blood vessels that breaks down fat cells (Seip et al., 1998), or glucose transport proteins, which help remove glucose sugars from the blood stream. Regardless, these findings make it clear that exercise alone is not enough – we also need to reduce our sedentary behavior and increase our motion.
Overcoming the sedentary lifestyle of work
The study design of 4 days of sedentary time followed by 1 hour of vigorous exercise model a week that is familiar for many people; a sedentary desk job during the week, and then a sudden increase in physical activity on the weekend. Therefore, the ‘weekend warrior’ who is sedentary during the week and active on the weekends may not see positive health effects from their physical activity due to metabolic resistance. In addition, the sedentary behavior often seen in workplaces (i.e., sitting at a desk) coupled with meals is increasing the risk of employee diabetes, atherosclerosis and cardiovascular disease.
The risk for diabetes
Those with diabetes are at an extra-high risk for these negative responses to meals. Diabetes is an alarming problem that affects 422 million people (and counting) worldwide, and is a leading contributor towards negative health effects, including disabilities and death. Those who do not currently have diabetes are not immune to the negative connection between sedentary behavior and diabetes. A meta-analysis of 18 studies (Healy et al.) showed that people with high levels of sedentary behavior have a 112% higher diabetes risk than those with low levels.