Even on days when you’re not training, your body is still doing an extraordinary amount of work

behind the scenes. Energy needs don’t suddenly drop just because you’re not exercising. In fact,

rest days are when much of the repair, recovery, and adaptation from training actually occurs.

Here’s what that means for your nutrition.

Energy Balance Basics

Energy Intake = The calories you consume through food and beverages

Energy Expenditure = The calories your body uses to sustain life and support activity

Many factors influence both sides of this equation. For example: metabolism and organ function to

hormones, emotional state, and movement (intentional or not).

Where Does Energy Go on “Rest” Days?

Even without exercise, your body uses energy in the following ways without accounting for activity or

digestion:

Key Components of Total Daily Energy Expenditure (TDEE)

Resting Metabolic Rate (RMR): ~70% of daily energy needs. Includes: organ function, temperature

regulation, and cellular repair. RMR is influenced by body composition, hormones, age, sex, and

genetics.

Thermic Effect of Food (TEF): Energy is required to digest, absorb, and metabolize the nutrients you

eat. This accounts for ~10% of daily energy use.

Non-Exercise Activity Thermogenesis (NEAT): Includes posture, fidgeting, walking to class, etc.

NEAT is highly variable and can make up a significant portion of your day’s energy needs.

Exercise Energy Expenditure (ExEE): Includes intentional training and its recovery period, where

energy expenditure remains elevated.

Why Fueling on Rest Days Still Matter

Recovery Requires Fuel: Repairing muscle tissue, replenishing glycogen, restoring hormonal balance, and

supporting immune function all demand energy and nutrients.

Organ Function Doesn’t Pause: Your brain, heart, liver, kidneys, and endocrine system continue

functioning 24/7, with or without exercise.

Undereating Can Backfire: Inadequate energy intake can trigger neuroendocrine adaptations that slow

down metabolism, increase food preoccupation, elevate stress hormones, and impair performance.

The Body Fights Back Against Energy Deficits

Your body is wired to defend against weight loss and perceived starvation. When intake is too low, even on

rest days, the brain (via the hypothalamus) and hormones like leptin and insulin activate powerful

mechanisms to conserve energy and drive food-seeking behavior.

Your metabolism is dynamic, not static - and it adapts to your environment, including your fuel availability.

Key Points

Rest days are not days to restrict. They’re an essential part of the training cycle, and they require

just as much, if not more, nutrition support to:

Promote recovery and adaptation
Prevent injury and burnout
Support hormonal and metabolic function
Keep you mentally and emotionally regulated

Sources:

Dunford, Marie, and Gretchen A. Farrell. Sports Nutrition: A Handbook for Professionals. 6th ed., Academy of Nutrition and Dietetics,

2018.

2. “Where Do Calories Go?!” Marci RD Nutrition Consulting, 2011. Adapted from Winning the War Within. PowerPoint presentation.

Why Calorie Needs Stay High on Rest Days: Understanding the Nuances of Energy Balance