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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.
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Precompetition taper and nutritional strategies: special reference to training during Ramadan intermittent fast.
Mujika, I, Chaouachi, A, Chamari, K
British journal of sports medicine. 2010;(7):495-501
Abstract
A marked reduction in the training load in the lead-up to major competitions allows athletes to reduce the fatigue induced by intense training and improve competition performance. This tapered training phase is based on the reduction in training volume while maintaining pretaper training intensity and frequency. In parallel to training load reductions, nutritional strategies characterised by lowered energy intakes need to be implemented to match lowered energy expenditure. The Ramadan intermittent fast imposes constrained nutritional practices on Muslim athletes, inducing a shift to a greater reliance on fat oxidation to meet energy needs and a possible increase in protein breakdown. The training load is often reduced during Ramadan to match the absence of energy and fluid intake during daylight, which implies a risk of losing training induced adaptations. Should coaches and athletes decide to reduce the training load during Ramadan, the key role of training intensity in retaining training induced adaptations should be kept in mind. However, experienced elite Muslim athletes are able to maintain their usual training load during this month of intermittent fasting without decrements in measures of fitness and with only minor adverse effects.
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Exercise and postprandial lipemia: effect of continuous compared with intermittent activity patterns.
Miyashita, M, Burns, SF, Stensel, DJ
The American journal of clinical nutrition. 2006;(1):24-9
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Abstract
BACKGROUND Guidelines state that accumulated physical activity is beneficial for health, but a minimum duration of 10 min per activity bout is recommended. Limited information regarding the effects of short (< 10 min) bouts of activity on health is available, and no studies of the effects of such short bouts of activity on postprandial lipemia have been conducted. OBJECTIVE The objective was to compare the effects of accumulating ten 3-min bouts of exercise with those of one 30-min bout of exercise on postprandial plasma triacylglycerol concentrations. DESIGN Ten men aged 21-32 y completed three 2-d trials > or = 1 wk apart in a randomized repeated-measures design. On day 1, the subjects rested (no exercise) or ran at 70% of maximum oxygen uptake in either ten 3-min bouts (30 min rest between each) or one continuous 30-min bout. On day 2, the subjects rested and consumed test meals (0.69 g fat, 0.95 g carbohydrate, 0.31 g protein, and 46 kJ/kg body mass) for breakfast and lunch. Venous blood samples were obtained in the fasted state and for 7 h postprandially on day 2. RESULTS Postprandial plasma triacylglycerol concentrations were lower throughout day 2 of both the accumulation exercise trial and the continuous exercise trial than during the control trial (main effect of trial: P < 0.001, 2-factor analysis of variance). CONCLUSIONS Accumulating multiple short bouts of exercise throughout the day effectively reduce postprandial plasma triacylglycerol concentrations to an extent similar to that of a single 30-min session of exercise in healthy young men.