Key Takeaways
- Three ways to expend energy:
- Rest: about 60-70%, relatively fixed.
- Digest: about 10%, relatively fixed.
- Activity: 15-30%, variable.
- Activity consists of two components.
- Exercise = intentional activities.
- Non-exercise = unplanned physical activities.
- Increasing non-exercise activity is easier than increasing exercise activities.
- Requires less structure and planning.
- Accumulates throughout the day.
- How to increase non-exercise activities.
- Limit sitting.
- Increase standing and walking.
- Practical strategies.
- Adjust work environment (standing desk), leisure time (dog walks), take the stairs (skip a step).
The Simple Math
Illustrative example of estimated energy expenditure.
- Increasing NEAT:
- 5 hr standing = +100 kcal, or about 4% increase.
- 2 hr walking = +300 kcal, or about 12% increase.
- Increasing EAT:
- 1 hr of running = +550 kcal, or 20% increase.
Key Concepts
Components of energy expenditure: BMR + DIT + AT.
- Basal Metabolic Rate (BMR) – about 60-70% of total.
- Expenditure at rest.
- Minimal amount of energy expended for homeostatic processes.
- Not actively digesting food.
- Breathing, blood circulation, controlling body temperature, cell growth, brain and nerve function, and contraction of muscles.
- Liver (27%), brain (19%), muscle (18%), kidneys (10%), heart (7%), other (19%).
- Correlated with fat-free or lean body mass.
- 1–2% decline per decade after age 20, mostly due to loss of fat-free mass.
- Conversely, increasing muscle increases BMR.
- Expenditure at rest.
- Diet-Induced Thermogenesis (DIT) – about 10% of total.
- Digestion, absorption and storage of food.
- Does not vary greatly between individuals.
- Varies with nutrient composition and energy content of consumed foods.
- Carbs (5-15% of consumption), protein (20-35%), fats (5-15%).
- Digestion, absorption and storage of food.
- Activity Thermogenesis (AT) – about 15-30% of total.
- Expenditure associate with any activity.
- Varies widely, both within and among individuals.
- Expenditure associate with any activity.
Components of Activity Thermogenesis: EAT + NEAT
- Exercise Activity Thermogenesis (EAT).
- Purposeful physical activity undertaken for health.
- For many, represents only about 0-100 kcal per day.
- For regular exercisers, increases to maximum of 15-30% of total expenditure.
- Non-Exercise Activity Thermogenesis (NEAT).
- All physical activities other than volitional sporting-like exercise.
- Unplanned and unstructured low grade physical activities.
- Maintaining and changing posture, walking, etc.
- For many, NEAT is the predominant component of AT.
Variation in energy expenditure
- Total energy expenditure varies substantially.
- Even for people with similar body types.
- Can vary by up to 2,000 kcal per day for adults of similar size.
- BMR, DIT or EAT can’t explain this variability.
- BMR: tends to be similar for similar body types.
- DIT: also varies little among individuals.
- EAT: small contribution for most people (0-100 kcal per day).
- NEAT likely main driver of variability in energy expenditure.
How do the numbers work?
- Total daily expenditure.
- Total = BMR + DIT + EAT + NEAT.
- BMR.
- Formulas – Mifflin-St Jeor
- Men: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5
- Women: 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) – 161
- Formulas – Aragon
- Men and women: 25.3 x lean body mass
- Average:
- Men: 1,800 kcal/day.
- Women: 1,400 kcal/day.
- Formulas – Mifflin-St Jeor
- DIT.
- Formula:
- BMR / 0.7 (70% of total expenditure) x 0.1
- Average:
- Men: 260 kcal/day.
- Women: 200 kcal/day.
- Formula:
- EAT.
- Dependent on activity type and duration.
- Can be expressed as multiple of BMR.
- Running (5 mph) = 8.3 x BMR.
- Energy added to BMR for 1 hr = 1/24 x (8.3 – 1) x 1,8000 = about +550 kcal.
- Examples.
- Running (1 hr, 5 mph): @ 8.3 x BMR = +550 kcal.
- Swimming (1 hr, moderate): @ 5.8 x BMR = +360 kcal.
- Cycling (1 hr, moderate): @ 7.5 x BMR = +500 kcal.
- Average.
- In reality, for most about not above 100 kcal/day.
- Dependent on activity type and duration.
- NEAT.
- Dependent on activity type and duration.
- Similarly expressed as multiple of BMR.
- Examples.
- Standing (1 hr): @ 1.3 x BMR = +20 kcal.
- Walking (1 hr, 3 mph): @ 3 x BMR = +150 kcal.
- Average.
- Unclear, varies a lot.
- Perhaps in the 200-400 kcal/day range.
- Dependent on activity type and duration.
Factors driving NEAT
- Gender
- Men tend to be more active than women.
- Body composition.
- Obese people tend to have lower levels of NEAT.
- Occupation.
- Trend towards less physically demanding, more sedentary work.
- Seasonal variation.
- Higher activity level in summer.
Increasing NEAT
- Potentially “easy” way to stimulate higher energy expenditure.
- Requires less structure and planning than exercise (EAT).
- Accumulates throughout the day.
- Contributes meaningfully to weight loss (practical solution for obesity).
- Reduce sitting.
- Sitting does not increase energy expenditure substantially (above BMR).
- Sitting may contribute to disease risk.
- Increase standing and walking time.
- Examples:
- Standing (depending on activity): 1.1-1.5 x BMR.
- (So, extra energy = +0.1-0.5 x BMR).
- Walking (depending on speed): 2-3 x BMR.
- Stairs: 5x BMR.
- Standing (depending on activity): 1.1-1.5 x BMR.
- Examples:
- Practical strategies.
- Enhance (office) environment.
- Self-monitor (pedometer).
Sources:
- Non-Exercise Activity Thermogenesis, The Crouching Tiger Hidden Dragon of Societal Weight Gain
- Non-exercise activity thermogenesis (NEAT): a component of total daily energy expenditure
- Compendium of Physical Activities