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Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans.
Ravussin, E, Beyl, RA, Poggiogalle, E, Hsia, DS, Peterson, CM
Obesity (Silver Spring, Md.). 2019;(8):1244-1254
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Abstract
OBJECTIVE Eating earlier in the daytime to align with circadian rhythms in metabolism enhances weight loss. However, it is unknown whether these benefits are mediated through increased energy expenditure or decreased food intake. Therefore, this study performed the first randomized trial to determine how meal timing affects 24-hour energy metabolism when food intake and meal frequency are matched. METHODS Eleven adults with overweight practiced both early time-restricted feeding (eTRF) (eating from 8 am to 2 pm) and a control schedule (eating from 8 am to 8 pm) for 4 days each. On the fourth day, 24-hour energy expenditure and substrate oxidation were measured by whole-room indirect calorimetry, in conjunction with appetite and metabolic hormones. RESULTS eTRF did not affect 24-hour energy expenditure (Δ = 10 ± 16 kcal/d; P = 0.55). Despite the longer daily fast (intermittent fasting), eTRF decreased mean ghrelin levels by 32 ± 10 pg/mL (P = 0.006), made hunger more even-keeled (P = 0.006), and tended to increase fullness (P = 0.06-0.10) and decrease the desire to eat (P = 0.08). eTRF also increased metabolic flexibility (P = 0.0006) and decreased the 24-hour nonprotein respiratory quotient (Δ = -0.021 ± 0.010; P = 0.05). CONCLUSIONS Meal-timing interventions facilitate weight loss primarily by decreasing appetite rather than by increasing energy expenditure. eTRF may also increase fat loss by increasing fat oxidation.
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Frequency of Breaks in Sedentary Time and Postprandial Metabolic Responses.
Hawari, NS, Al-Shayji, I, Wilson, J, Gill, JM
Medicine and science in sports and exercise. 2016;(12):2495-2502
Abstract
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 normoglycemic overweight/obese men (age, 33 ± 13 yr; body mass index, 28.3 ± 3.0 kg·m; mean ± SD) each participated in three experimental trials in random order, in which they arrived fasted, then consumed a test breakfast (8 kcal·kg body weight, with 37% energy from fat, 49% from carbohydrates, 14% from protein) and, 4 h later, an identical test lunch. Expired air and blood samples were taken fasted and for 8 h postprandially. In one trial (uninterrupted sitting), participants sat continuously throughout the observation period; in the prolonged standing (PRO-Stand) trial, participants stood still for 15 min every 30 min; and in the intermittent standing trial (INT-Stand), they stood for 1.5 min, 10 times every 30 min. RESULTS Compared with uninterrupted sitting, 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, normoglycemic, overweight/obese men.