It's a Japanese proverb (maxim?) - the way I understand it, it's meant for everyone, to eat the correct amount for good health.
I guess my main question for Catrin would also be the accuracy of your calorie expenditure calculations. Have you used a power meter to calibrate your HRM results, or done a calorimetry where they collect your breath on a treadmill or stationary bike? Calories can be converted to watt-hours, but without measuring something, whether it's your power output or your O₂/CO₂ exchange, estimates are about as accurate as estimating your maximum HR based on your age - that is, not very accurate at all.
Speed comes from what you put behind you. - Judi Ketteler