What Is Resting Energy?

Resting energy (also called resting energy expenditure) refers to the energy your body consumes to maintain life and basic functions during a day with minimal activity.

Resting Energy ≈ Basal Metabolism + Very Low-Level Activity Expenditure

Resting energy primarily comes from basal metabolism and includes a small amount of additional expenditure from minimal daily activities (such as sitting, standing, or light walking).

Why Is Resting Energy Important?

Resting energy typically accounts for 60%–75% of total daily energy expenditure and is the most stable and fundamental part of your body's energy consumption.

It helps you:

  • Understand your body's baseline energy needs
  • More accurately assess daily calorie balance (whether you're eating too much or too little)
  • Serve as an important reference for evaluating metabolic rate, body composition changes, and health status

When exercise levels are low or daily activities are relatively consistent, changes in resting energy often better reflect changes in your body's condition.

Reference Range for Resting Energy

Resting energy varies significantly based on gender, age, height, weight, and muscle mass. The following are common reference ranges:

  • Females: approximately 1200 – 1600 kcal / day
  • Males: approximately 1500 – 2000 kcal / day

If your resting energy is significantly higher or lower than others with similar body types, it's usually related to muscle mass, metabolic state, or recent lifestyle changes, rather than simply how much you exercise.

How Does Apple Watch Measure Resting Energy?

Apple Watch's resting energy is based on comprehensive estimates using personal information and all-day physiological data, not direct measurement of calorie burning.

Main factors include:

  • Basic information such as age, gender, height, and weight
  • Heart rate data during resting and daily states
  • All-day activity levels and wearing duration

When you're at rest or in a low-activity state, the system attributes energy expenditure to resting energy; when activity intensity exceeds resting levels, additional expenditure is attributed to active energy.