Exercise — Non-Exercise Activity Thermogenesis (NEAT)

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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.

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  • 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.
  • 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%).
  • Activity Thermogenesis (AT) – about 15-30% of total.
    • Expenditure associate with any activity.
      • Varies widely, both within and among individuals.

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.
  • DIT.
    • Formula:
      • BMR / 0.7 (70% of total expenditure) x 0.1
    • Average:
      • Men: 260 kcal/day.
      • Women: 200 kcal/day.
  • 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.
  • 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.

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.
  • Practical strategies.
    • Enhance (office) environment.
    • Self-monitor (pedometer).

Sources:

 

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