Table 2.

Equations to estimate energy availability.

Abbreviations	Equation or definition	Units
FFM: fat-free mass	$\mathrm{FFM}=\mathrm{body}\mathrm{mass}-\mathrm{body}\mathrm{fat}\mathrm{mass}$ a	kg
RMR: resting metabolic rate
RMR, female adult aged ≥18 years:	Harris and Benedict (35)	${\displaystyle \frac{\mathrm{kcal}}{\mathrm{day}}}$
RMR, female adolescent aged 14–17.9 years:	bSchofield (36) − 5%
RMR per minute	${\displaystyle \frac{\mathrm{RMR}}{\min }=\mathrm{RMR}\cdot \frac{1\mathrm{day}}{1440\min }}$	${\displaystyle \frac{\mathrm{kcal}}{min}}$
METs: metabolic equivalent of tasks	Databases. Adult: Ainsworth et al. (37). Adolescent: Butte et al. (38).
TPA: training + physical activity	activity ≥4 METs + 3.5–3.9 METs if completed for ≥10 min·day−1
cTECsA: total energy cost of a specific activity (sA)	${\displaystyle \mathrm{TECsA}=(\mathrm{MET}\mathrm{sA})\frac{\mathrm{RMR}}{\min }(min\mathrm{sA})}$	kcal
TECE: total energy cost of exercise “TPA”	$\mathrm{TECE}=\mathrm{\Sigma }\mathrm{TECsA}$	kcal
dECBANE: energy cost of being awake but not exercising, during the time engaged in TPA	${\displaystyle \mathrm{ECBANE}=1.3\cdot \frac{\mathrm{RMR}}{\min }\cdot \frac{min\mathrm{TPA}}{\mathrm{day}}}$	${\displaystyle \frac{\mathrm{kcal}}{\mathrm{day}}}$
EEE: exercise “TPA” energy expenditure	$\mathrm{EEE}=\mathrm{TECE}-\mathrm{ECBANE}$	${\displaystyle \frac{\mathrm{kcal}}{\mathrm{day}}}$
EA: energy availability EI: dietary energy intake	${\displaystyle \mathrm{EA}=\frac{\mathrm{EI}-\mathrm{EEE}}{\mathrm{FFM}}}$	${\displaystyle \frac{\mathrm{kcal}}{\mathrm{kg}\mathrm{FFM}\cdot \mathrm{day}}}$

^a Body fat percentage, to estimate body fat mass, as per the equation in Yuhasz (39) that requires 6 skinfolds.

^b Predicts RMR from body mass.

^c As per Butte et al. (38).

^d Factor 1.3 for adults, but 1.33 for adolescents.