Key Takeaways
- The WHO recommends 150-300 minutes of moderate-intensity or 75-150 minutes of vigorous-intensity physical activity per week for adults, plus 2+ days of muscle-strengthening exercises.[1]
- MET values (Metabolic Equivalents) quantify energy expenditure: 1 MET = resting metabolic rate. Activities range from 1.0 (sitting) to 15+ (sprinting).[2]
- The calorie burn formula is straightforward: Calories = MET × Body Weight (kg) × Duration (hours).[2]
- The IPAQ (International Physical Activity Questionnaire) classifies activity into Low, Moderate, or High categories based on walking, moderate, and vigorous activity patterns.[3]
- Physical inactivity is the fourth leading risk factor for global mortality, accounting for approximately 3.2 million deaths annually.[1]
What Is Physical Activity?
Physical activity is any bodily movement produced by skeletal muscles that results in energy expenditure above resting levels.[1] This includes everything from formal exercise (running, lifting weights, swimming) to everyday activities like walking to work, climbing stairs, gardening, and household chores.
The distinction between physical activity and exercise matters: exercise is a planned, structured, repetitive subset of physical activity aimed at improving fitness. Both count toward your health targets. Research consistently shows that all movement matters — even replacing sedentary time with light activity provides measurable health benefits.[4]
WHO 2020 Physical Activity Guidelines
The World Health Organization updated its global guidelines in 2020, shifting from a minimum threshold to a continuum of benefits: “some physical activity is better than none, and more is generally better.”[1] The key recommendations for adults aged 18-64:
Aerobic Activity
150-300 minutes of moderate-intensity OR 75-150 minutes of vigorous-intensity per week, or an equivalent combination.
Muscle Strengthening
2 or more days per week involving all major muscle groups at moderate or greater intensity.
Sedentary Reduction
Limit the amount of time spent being sedentary. Replace sedentary time with any intensity of activity.
Beyond Optimal
Adults who exceed 300 minutes of moderate-equivalent activity gain additional health benefits.
Vigorous = 2× Moderate
1 minute of vigorous activity counts as 2 minutes of moderate activity. So 75 minutes of vigorous exercise is equivalent to 150 minutes of moderate exercise in terms of health benefits.[1]
Understanding MET Values
A MET (Metabolic Equivalent of Task) represents the energy cost of physical activities. One MET is defined as the rate of energy expenditure at rest: approximately 1 kcal per kg of body weight per hour, or 3.5 mL of oxygen per kg per minute.[2]
Activities are classified by their MET values: Light(<3 METs) includes sitting, standing, and slow walking. Moderate (3-5.9 METs) includes brisk walking, cycling, and swimming at a moderate pace. Vigorous (≥6 METs) includes running, fast cycling, and intense sports.[2]
| Activity | MET | Intensity | kcal/hr (75 kg) |
|---|---|---|---|
| Sitting quietly | 1.0 | Sedentary | 75 |
| Walking, casual (2 mph) | 2.0 | Light | 150 |
| Walking, brisk (3.5 mph) | 3.5 | Moderate | 263 |
| Cycling, moderate | 5.5 | Moderate | 413 |
| Swimming, laps | 6.0 | Vigorous | 450 |
| Running, 6 mph | 9.8 | Vigorous | 735 |
| Running, 8 mph | 11.8 | Vigorous | 885 |
IPAQ Activity Classification
The International Physical Activity Questionnaire (IPAQ) is a validated tool used globally to assess physical activity levels in populations.[3] The short form measures walking, moderate, and vigorous activity, then classifies individuals into three categories:
| Category | Criteria (any one met) |
|---|---|
| Low | Does not meet Moderate or High criteria. |
| Moderate | 3+ days vigorous ≥ 20 min/day, OR 5+ days moderate/walking ≥ 30 min/day, OR ≥ 600 MET-min/week combined. |
| High | ≥ 1500 vigorous MET-min/week on 3+ days, OR ≥ 3000 total MET-min/week on 7 days. |
Physical Activity Level (PAL) and TDEE
Your Physical Activity Level (PAL) is a ratio of your total daily energy expenditure to your basal metabolic rate. It provides a single number that characterizes your overall activity:[5]
- 1.2-1.4: Sedentary (desk job, little exercise)
- 1.4-1.6: Lightly Active (light exercise 1-2 days/week)
- 1.6-1.75: Moderately Active (moderate exercise 3-4 days/week)
- 1.75-2.0: Very Active (intense exercise 5-6 days/week)
- 2.0-2.4: Extremely Active (professional athletes, heavy physical labor)
Total Daily Energy Expenditure (TDEE) is calculated as: TDEE = BMR × PAL. This calculator uses the Mifflin-St Jeor equation for BMR, which is the most accurate validated equation recommended by the Academy of Nutrition and Dietetics:[6]
Males: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age + 5
Females: BMR = 10 × weight(kg) + 6.25 × height(cm) - 5 × age - 161
Health Benefits of Physical Activity
The evidence is overwhelming: regular physical activity reduces the risk of cardiovascular disease, type 2 diabetes, several cancers, depression, anxiety, and all-cause mortality.[1] Benefits begin with the first session and accumulate with consistency.
Cardiovascular Health
Reduces risk of heart disease by 20-35%. Lowers blood pressure and improves cholesterol profiles.
Mental Health
Reduces symptoms of depression by 20-30% and anxiety by 15-25%. Improves sleep quality and cognitive function.
Cancer Prevention
Reduces risk of colon cancer by 30-40% and breast cancer by 20-30%. Associated with lower risk of 7+ cancer types.
Metabolic Health
Reduces risk of type 2 diabetes by 40-60%. Improves insulin sensitivity and glucose regulation.
Bone & Muscle Health
Maintains bone density and reduces fracture risk. Preserves muscle mass and strength with aging.
Longevity
Meeting WHO guidelines associated with 3-7 additional years of life expectancy and reduced disability.
Risks of Sedentary Behavior
Sedentary behavior -- defined as any waking activity with energy expenditure ≤ 1.5 METs while sitting, reclining, or lying -- is an independent risk factor for poor health, even among people who exercise regularly.[4] Prolonged sitting is associated with:
- Increased all-cause mortality (relative risk 1.22-1.49 for highest vs lowest sedentary time)
- Higher cardiovascular disease incidence
- Increased risk of type 2 diabetes
- Greater incidence of depression
- Increased cancer risk (colon, endometrial, lung)
The key insight: breaking up prolonged sitting with even light activity (standing, walking for 2-3 minutes every 30-60 minutes) can significantly reduce these risks, independent of total exercise time.
Getting Started: A Practical Guide
If you're currently inactive, the most effective approach is gradual progression. Research shows that the greatest health gains come from moving from “no activity” to “some activity” -- even 60-75 minutes per week provides significant benefits.[1]
Weeks 1-2
10-15 minutes of walking daily. Focus on consistency, not intensity. Aim for after meals.
Weeks 3-4
20-30 minutes daily. Increase pace to brisk walking (3.5+ mph). Add a weekend activity you enjoy.
Weeks 5-6
Add 2 days of bodyweight exercises (squats, push-ups, lunges). 10-15 min each session.
Weeks 7-8
Reach the WHO minimum: 150 min moderate activity + 2 strength days. You're meeting global guidelines.
Frequently Asked Questions
Sources & References
- WHO Guidelines on Physical Activity and Sedentary Behaviour. World Health Organization. WHO (2020)
- 2024 Adult Compendium of Physical Activities. Ainsworth BE, Haskell WL, Herrmann SD, et al.. Journal of Sport and Health Science (2024)
- International Physical Activity Questionnaire: Reliability and Validity. Craig CL, Marshall AL, Sjöström M, et al.. Medicine & Science in Sports & Exercise (2003)
- Sedentary Behaviour and Health: Mapping Environmental and Social Contexts. Owen N, Salmon J, Koohsari MJ, Turrell G, Giles-Corti B. British Journal of Sports Medicine (2014)
- Human Energy Requirements: Report of a Joint FAO/WHO/UNU Expert Consultation. FAO/WHO/UNU. FAO Food and Nutrition Technical Report Series (2001)
- Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Adults. Mifflin MD, St Jeor ST, Hill LA, et al.. American Journal of Clinical Nutrition (1990)
- Physical Activity and Public Health: Updated Recommendation for Adults. Haskell WL, Lee IM, Pate RR, et al.. Medicine & Science in Sports & Exercise (2007)
- Physical Activity, Fitness, and Health: International Proceedings and Consensus Statement. Bouchard C, Shephard RJ, Stephens T. Human Kinetics Publishers (1994)
- Research Paper on Physical Activity and Fitness Patterns Among University Students. Various authors. ResearchGate (2020)
- Physical Activity for Health. National Center for Biotechnology Information. NCBI Bookshelf
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Disclaimer: This tool is for informational and personal journaling purposes only. Results are estimates based on published formulas and may vary based on individual factors such as genetics, training history, and measurement technique.