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20-02-2013 | Sports medicine | Article

Recommendations for metabolic health may need changing

Abstract

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medwireNews: One hour of physical exercise daily is not enough to compensate for the negative effects of inactivity on insulin sensitivity and plasma lipids if the rest of the day is spent sitting, show study findings.

"Vice versa, with nearly identical DEE [daily energy expenditure], reducing sitting time by walking/standing was more effective in improving insulin level and lipid parameters than 1 hour of moderate to vigorous bicycle exercise," say Hans Savelberg (Maastricht University, the Netherlands) and team. "This novel observation may have important health policy implications," they add.

Current guidelines on the prevention of diabetes and cardiovascular disease promote engaging in at least half an hour of moderate to vigorous physical activity at least 5 days per week. However, "they do not answer the question if, when DEE is held constant, such short bouts of exercise can compensate for the negative metabolic effects of inactivity," note Savelberg et al.

For the study, 18 healthy individuals, aged a mean of 21 years, followed three activity regimens that each lasted 4 days.

A sitting regime involved individuals sitting for 14 hours per day, walking for 1 hour per day, and standing for 1 hour per day. In the exercise regime, 1 hour of sitting was replaced by 1 hour of vigorous exercise on a bicycle while the rest of the day was spent as during the sitting regime. In the third regime, of minimal physical activity (PA), individuals did not exercise vigorously but were asked to replace 6 hours of sitting with 4 hours of walking at a leisurely pace and 2 hours of standing.

As reported in PLoS ONE, the estimated DEE was about 500 kcal higher during the exercise and minimal PA regimens than in the sitting regimen, whereas it was only very slightly higher, by about 73 kcal, during the minimal intensity PA than the exercise regime.

The morning after the regimens had ended, the area under the receiver operating characteristics curve for insulin during an oral glucose tolerance test was significantly lower after the minimal intensity PA regime compared with both the sitting and exercise regimes, at 6727.3 versus 7752.0 and 8320.4 mU per min/mL, respectively.

Furthermore, triglyceride, non-high-density lipoprotein cholesterol, and apolipoprotein B plasma levels were significantly improved after the minimal intensity PA regime, compared with the sitting regime, and showed trends for improvement compared with the exercise regime.

"Our study suggests that in addition to health interventions that stress the importance of spending enough energy to maintain a neutral energy balance, a minimal daily amount of nonsitting time should also be promoted," concludes the team.

By Sally Robertson, medwireNews Reporter

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