Physical Activity, Exercise & Weight Loss

Dr.ANUPA BASNET Clinical Nutritionist and Counsellor

Mechanisms and Facts

Obesity is not a curse but largely a lifestyle disease that can be prevented and managed. The foundation of obesity is often laid early in life when excessive calories are fed to children in the belief that “a plump child is a healthy child.” However, feeding beyond a child’s ideal nutritional requirement leads to overproduction and enlargement of fat cells.

Fat cells formed during childhood do not disappear later in life. Therefore, preventing overfeeding during infancy and childhood is essential for long-term health.

Types of Obesity

Obesity is broadly classified into two types based on fat cell development:

1. Juvenile-Onset Obesity (Hyperplastic Type)

In this type, fat cells increase in number due to excessive calorie intake during childhood. Since fat cells multiply rapidly during the first few years of life, overeating at this stage lays the foundation for lifelong obesity.

2. Adult-Onset Obesity (Hypertrophic Type)

Here, the number of fat cells remains relatively constant, but the existing fat cells enlarge due to excess fat storage caused by overeating.

Weight loss is generally easier in hypertrophic obesity, highlighting the importance of physical activity and exercise in adults.

BMI Classification

Obesity is also classified using BMI (Body Mass Index):

• Normal BMI: 18–25
• Grade I Obesity: 25–29.9
• Grade II Obesity: 30–39.9
• Grade III Obesity: Above 40

Causes of Obesity

Obesity can result from several factors including:

• Genetics
• Age and sex
• Eating habits
• Stress
• Endocrine disorders
• Certain medications
• Trauma
• Lifestyle and prosperity
• Physical inactivity

Genetics may increase risk; if both parents are obese, a child has nearly an 80% chance of becoming obese. However, while genetics cannot be changed, physical inactivity can be modified. As the saying goes, “Exercise is a celebration of what your body can do, not a punishment for what you ate.”

How Exercise Helps in Weight Loss

The hypothalamus in the brain regulates hunger and satiety. The feeding center stimulates hunger, while the satiety center suppresses appetite.

During exercise, several hormones and chemical compounds influence these centers:

• Ghrelin (hunger hormone) decreases
• Peptide YY (PYY) increases, promoting fullness
• Leptin, produced by adipose tissue, signals satiety to the brain

Ghrelin and PYY are produced in the stomach and digestive system and vary depending on whether the stomach is empty or full.

Cold exposure during exercise may temporarily suppress appetite because the sympathetic nervous system redirects blood flow away from the digestive tract toward vital organs. Digestion slows down and fullness may persist longer. However, this effect is temporary, and appetite may later rebound to restore energy balance.

Understanding METS

METS (Metabolic Equivalents) measure how much energy the body uses during physical activity.

1 MET equals the energy used while sitting quietly at rest, which is approximately:

• 3.5 ml oxygen/kg/minute
• About 1 kcal/kg/hour

Thus, a 60 kg individual burns approximately 60 kcal/hour per MET.

Exercise Intensity Categories

• <3 METS: Light activity
• 3–6 METS: Moderate activity
• >6 METS: Vigorous activity

METS help estimate:

• Exercise intensity
• Calories burned
• Fitness level
• Cardiac rehabilitation targets

Recommended Physical Activity

The Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine recommend at least 30 minutes of moderate-intensity physical activity on most days of the week.

Moderate-intensity activity generally ranges between 3–6 METS and includes brisk walking at 3–4 miles per hour. Activities such as tennis, stair climbing, cycling, swimming, gardening, and household chores also fall within this range.

According to the National Institute of Nutrition (NIN), India, adults above 20 years should engage in 30–45 minutes of moderate physical activity, such as brisk walking at 5–6 km/hour, for at least 5–6 days per week.

Regular physical activity not only supports weight management but also:

• Lowers blood pressure
• Reduces serum triglycerides
• Raises HDL (“good”) cholesterol
• Improves overall cardiovascular health

Inactive individuals above 40 years of age, especially those at risk for heart disease or diabetes, should consult a physician before beginning vigorous exercise such as running or intense swimming.

Importance of Warm-Up and Cool-Down

Every exercise session should include:

• Warm-up: 5–10 minutes
• Cool-down: 5–10 minutes

Warm-ups gradually increase heart rate and blood flow to muscles, making them more flexible and reducing the risk of injury.

Cooling down is equally important because sudden stoppage of exercise can lead to pooling of blood in muscles, causing dizziness, nausea, fainting, or abnormal heart rhythms due to reduced blood supply to the brain.

During exercise, heart rate should ideally increase by 60–70% of the predicted maximum heart rate.

Simple Lifestyle Modifications

Modern sedentary lifestyles significantly increase the risk of chronic diseases and premature death. Even small lifestyle changes can make a major difference.

Some simple modifications include:

1. Stand or move for 10–15 minutes after every hour of sitting.
2. Use stairs instead of elevators whenever possible.
3. Walk short distances instead of using vehicles.
4. Walk inside the office during breaks.
5. Stand while watching television for a few minutes.
6. Reduce children’s screen time.
7. Encourage workplace movement through shared pantry spaces instead of room service.

According to Dr. Michael Greger, prolonged sitting is associated with endothelial dysfunction, shorter lifespan, and increased mortality risk. Studies show that individuals who sit for prolonged hours daily have significantly higher death rates compared to those who remain physically active.

Conclusion

Physical activity and exercise should become an essential part of daily life. Even 30–45 minutes of moderate exercise each day can provide enormous physical and mental health benefits.

Movement truly brings life.