Frequency of breaks in sedentary time and postprandial metabolic responses

Purpose: To compare the metabolic effects of breaking up sedentary time with prolonged periods of standing versus multiple shorter standing bouts with the same total duration to determine whether, in principle, altering the frequency of ‘standing breaks’ in sedentary time, influences metabolic responses over the course of the day. Methods: Ten normoglycaemic overweight/obese men (age 33±13 years; BMI 28.3±3.0 kg.m2; mean±SD) each participated in three experimental trials in random order, in which they arrived fasted, then consumed a test breakfast (8 kcal.kg-1 body weight, with 37% energy from fat, 49% from carbohydrates, 14% from protein) and, 4 hours later, an identical test lunch. Expired air and blood samples were taken fasted and for eight hours postprandially. In one trial (SIT) participants sat continuously throughout the observation period; in the prolonged standing trial (PRO-Stand), participants stood still for 15 minutes every 30 minutes; and in the intermittent standing trial (INT-Stand), they stood for 1.5 minutes, 10 times every 30 minutes. Results: Compared to SIT energy expenditure was 320±62 kJ (10.7±2.0%) higher in PRO-Stand and 617±76 kJ (20.4±2.3%) higher in INT-Stand: energy expenditure in INT-Stand was 296±78 kJ (9.0±2.3%) higher than PRO-Stand (mean±SEM; all p<0.001). However, there were no significant differences between trials in postprandial glucose, insulin or triglyceride responses. Conclusions: These data demonstrate an independent effect of frequency of sedentary breaks on energy expenditure which provides an explanation for the association between frequency of sedentary breaks and adiposity observed in epidemiological data. However, it may be necessary to break up sitting with activities of greater intensity than quiet standing to positively influence glucose, insulin and triglyceride metabolism in relatively young, normoglycaemic overweight/obese men