The efficacy of a home-use metabolic device (Lumen) in response to a short-term low and high carbohydrate diet in healthy volunteers

Figures & data

Figure 1. Comparison between fasted and post-meal (30 and 60 min) laboratory and Lumen device measures: (a) blood glucose (mmol·L⁻¹); (b) expired air respiratory exchange ratio (RER); and (c) Lumen%CO₂ (L%CO₂). *** Denotes significant difference between paired timepoints (P ≤ 0.003). **** Denotes significant difference between paired timepoints (P < 0.001).

Table 1. Mean Douglas bag data for fasted and post-meal respiratory measures.

Variable	Fasted	P30	P60
FEO2 (%)	18.27 ± 0.20	18.44 ± 0.19	18.39 ± 0.18
FECO2 (%)	2.13 ± 0.12	2.30 ± 0.14*	2.26 ± 0.12
$\dot{\mathrm{V}}$E (L·min^−1)	13.62 ± 1.36	15.48 ± 1.31	17.19 ± 1.35*
$\dot{\mathrm{V}}$O2 (L·min^−1)	0.36 ± 0.03	0.38 ± 0.02	0.42 ± 0.02
$\dot{\mathrm{V}}$CO2 (L·min^−1)	0.28 ± 0.02	0.34 ± 0.02*	0.37 ± 0.02*
RER	0.77 ± 0.03	0.91 ± 0.02*	0.86 ± 0.02*

Data presented as mean ± SE. F_EO₂ (%) = fraction of expired oxygen (%); F_ECO₂ (%) = fraction of expired carbon dioxide (%); $\dot{\mathrm{V}}$_E = absolute minute ventilation (STPD); $\dot{\mathrm{V}}$O₂ = absolute oxygen consumption standardized; $\dot{\mathrm{V}}$CO₂ (STPD) = absolute carbon dioxide standardized (STPD); RER = respiratory exchange ratio. * = significantly different to fasted (P ≤ 0.047).

Figure 2. Ordinary least squares regression between expired RER and Lumen %CO₂ (L%CO₂) for: (a) fasting and 30 min post-meal (P30); (b) fasting and mean post-meal data. Open circles indicate fasting measures; closed circles represent respective fed measures.

Table 2. Mean dietary intake at baseline and across intervention periods.

		NORM	LOW	HIGH
EI	(kcal·d^−1)	2196.3 ± 77.2	2270.9 ± 65.8	2236.3 ± 72.4
	(kcal·kg^−1·d^−1)	31.0 ± 1.3	32.2 ± 1.1	31.3 ± 1.3
CHO	(%EI)	41.7 ± 1.9 *	19.9 ± 0.6	56.3 ± 0.8 ^#
	(g·d^−1)	231.3 ± 14.4 *	113.2 ± 4.9	315.4 ± 12.3 ^#
	(g·kg^−1·d^−1)	3.3 ± 0.2 *	1.6 ± 0.1	4.4 ± 0.2 ^#
PRO	(%EI)	18.0 ± 0.6 ^a	19.9 ± 0.3	19.3 ± 0.4
	(g·d^−1)	98.1 ± 4.0 ^b	113.2 ± 3.6	107.9 ± 3.9
	(g·kg^−1·d^−1)	1.4 ± 0.1 ^b	1.6 ± 0.1	1.5 ± 0.1
FAT	(%EI)	36.9 ± 1.6 *	57.7 ± 0.8	22.8 ± 0.6 ^#
	(g·d^−1)	89.4 ± 4.5 *	145.4 ± 4.3	56.2 ± 1.9 ^#
	(g·kg^−1·d^−1)	1.3 ± 0.1 *	2.1 ± 0.1	0.8 ± 0.0 ^#

Data presented as mean ± SE. NORM = normal dietary intake pre-intervention; LOW = low carbohydrate diet week; HIGH = high carbohydrate diet week. EI = caloric energy intake; CHO = carbohydrate; PRO = protein. * = significantly different to both LOW and HIGH (P < 0.001); ^# = significantly different to LOW (P < 0.001); ^a = significantly different to LOW only (P = 0.037); ^b = significantly different to both LOW and HIGH (P ≤ 0.03).

Table 3. Training load comparisons across dietary periods.

Variable	NORM	LOW	HIGH
sTIME (mins)	54.0 ± 2.1	58.9 ± 2.3	58.7 ± 3.3
sHR (b·min^−1)	133 ± 3	133 ± 4	132 ± 4
sRPE (0-10)	5.3 ± 0.2	5.4 ± 0.2	5.5 ± 0.2
TL (AU)	1581.4 ± 125.1	1666.0 ± 146.5	1676.9 ± 129.6
TM (AU)	1.3 ± 0.1	1.2 ± 0.1	1.2 ± 0.1
TS (AU)	1863.5 ± 227.3	1784.8 ± 211.3	1881.1 ± 218.4

Data presented as mean ± SE. sTIME = mean exercise session duration; sHR = mean session heart rate; sRPE = mean session perceived exertion rating using a 0–10 visual analogue scale; TL = mean weekly intervention training load (AU; arbitrary units); TM = mean weekly training monotony based on TL; TS = mean weekly estimated training strain.

Figure 3. Mean Lumen %CO₂ responses for NORM, LOW, and HIGH according to: (a) ~30 min post-waking fasted assessment; (b) ~45 min post-breakfast; (c) immediately before evening meal; (d) ~45 min post evening meal; and (e) immediately before bed. * Denotes significant difference between paired timepoints (P ≤ 0.043). ** Denotes significant difference between paired timepoints (P ≤ 0.009).

Figure 4. Mean Lumen Index responses for NORM, LOW, and HIGH according to: (a) ~30 min post-waking fasted assessment; (b) ~45 min post-breakfast; (c) immediately before evening meal; (d) ~45 min post evening meal; and (e) immediately before bed. AU = arbitrary units. * Denotes significant difference between paired timepoints (P ≤ 0.028). ** Denotes significant difference between paired timepoints (P ≤ 0.005).