I don't know who's G-Flux stuff you read, but the following studies are the ones often cited as "scientific proof" of the effects of it. But it just doesn't seem to add up that well.
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J Clin Endocrinol Metab. 2004 Jul;89(7):3573-8
High energy flux mediates the tonically augmented beta-adrenergic support of resting metabolic rate in habitually exercising older adults.
Bell C, Day DS, Jones PP, Christou DD, Petitt DS, Osterberg K, Melby CL, Seals DR.
Department of Integrative Physiology, 354UCB, University of Colorado, Boulder, CO 80309-0354, USA.
[email protected]
The sympathetic nervous system contributes to resting metabolic rate (RMR) via beta-adrenergic receptor (beta-AR) stimulation of energy metabolism. RMR and beta-AR support of
RMR are greater in habitually exercising compared with sedentary older adults possibly due to greater energy flux (magnitude of energy intake and energy expenditure during energy balance). In
10 older adults regularly performing aerobic endurance exercise (mean +/- se,
66 +/- 1 yr) compared with baseline, a reduction in energy flux (via abstention of exercise and proportional reduction in dietary intake) decreased (P < 0.05) energy expenditure (7746 +/- 440 vs. 9630 +/- 662 kJ.d(-1)), caloric intake (7808 +/- 431 vs. 9433 +/- 528 kJ.d(-1)), RMR (5192 +/- 167 vs. 5401 +/- 209 kJ.d(-1)), and skeletal muscle sympathetic nervous system activity (36 +/- 2 vs. 42 +/- 2 bursts.min(-1)). Significant beta-AR support of RMR was observed at baseline (167 +/- 42 kJ.d(-1)) but not during reduced energy flux. The change in RMR from baseline to reduced energy flux was related to the corresponding change in beta-AR support of RMR (r = 0.77, P = 0.009). No changes were observed in seven time controls (69 +/- 3 yr) who maintained energy flux. High energy flux is a key mechanism contributing to the elevated RMR and beta-AR support of RMR in habitually exercising older adults.
Maintenance of high energy flux via regular exercise may be an effective strategy for maintaining energy expenditure and preventing age-associated obesity.
I would say a pretty weak corrolation here for someone who is already regularly exercising and understands their requirements for energy balance.
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Am J Clin Nutr. 1995 Mar;61(3):473-81
Interaction of acute changes in exercise energy expenditure and energy intake on resting metabolic rate.
Bullough RC, Gillette CA, Harris MA, Melby CL.
Department of Food Science and Human Nutrition, Colorado State University, Fort Collins 80523.
The effects on resting metabolic rate (RMR) of energy intake and exercise energy expenditure were examined in eight trained men under four conditions:
1) high energy flux (HF), 90 min of exercise at 75% VO2max on 3 d while in energy balance; 2) low energy flux (LF), no exercise for 3 d while in energy balance; 3) negative energy balance (NEB), exercise on 3 d while consuming low-flux meals; and 4) positive energy balance (PEB), no exercise for 2 d while consuming high-flux meals. Eight untrained men were studied in LF. There were effects of exercise energy expenditure and energy intake on RMR, and an exercise x diet interaction (P < 0.05).
RMR was greater in trained than in untrained subjects only when trained subjects were in HF. These data indicate that RMR is influenced by exercise, energy intake, and their interaction and suggest that higher RMR in
trained vs untrained individuals results from acute effects of HF rather than from a chronic adaptation to exercise training.
This study cites high energy flux, but says the subjects were in "energy balance." So, where's the g-flux...?
