Prolonged Sedentary Time May Modulate Glycemic Response To A 12-week Dietary Intervention In Obesity

PURPOSE: To test the moderating effects of MVPA, ST, and prolonged ST on glycemic control response to a 12-week intervention increasing monounsaturated fat intake in 25-45 years old adults with overweight and obesity.

METHODS: This study included a subsample (N = 59, 36 ♀; Mage = 35.5 ± 6.1 yrs, BMI = 33.1 ± 5.8 kg·m-2) from a randomized-controlled trial (NCT02740439). The intervention group (INT; n = 24) consumed one avocado daily. The control group (CON; n = 35) was matched on caloric intake and meal composition except for the avocado. Glucose and insulin area under the curve, insulin sensitivity (Matsuda index, MI), and β-cell function (insulinogenic index) were measured pre- and post-intervention with an oral glucose tolerance test. MVPA (≥2,200 counts·min-1, CPM) and ST (<100 CPM) were assessed with a hip-worn ActiGraph wGT3X-BT accelerometer (7 days, waking hours), and expressed as % of wear time per day. Prolonged ST was defined as % wear time spent in sedentary bouts lasting ≥20 min. The moderating effects of baseline MVPA, ST, prolonged ST, and change in ST on post-intervention glycemic control were tested with ANCOVAs, controlling for outcomes at baseline, and visceral fat.

RESULTS: Groups did not differ in baseline MVPA (P = 0.07), but INT was more sedentary (ST: Mdiff = -4.73 ± 1.76 %, P = 0.01; prolonged ST: Mdiff = -7.66 ± 2.46 %, P = 0.003). ST increased in the CON (ΔM = 2.33 ± 0.96 %, P = 0.02) but not in the INT (P = 0.45). INT did not improve the indices of glycemic control (Ps ≥ 0.17). However, baseline prolonged ST moderated the intervention effect on MI (F(1,53) = 5.16, P = 0.024). INT and CON did not differ in MI within prolonged ST sub-groups (Ps ≥ 0.09). A trend in the lower prolonged ST sub-group suggested greater improvement in MI in the INT (ΔM = 1.2 ± 0.7, P = 0.09). No other interactions were noted (Ps ≥ 0.08).

CONCLUSIONS: These exploratory findings suggest that inter-individual variation in prolonged ST may be relevant to identifying responders to a dietary intervention. Studies designed to test moderating effects of physical behaviors on glycemic responses to dietary interventions are needed.