How can an 18-year-old weighing 200 jin (approximately 100 kg) lose weight safely and effectively?

For an 18-year-old individual weighing 200 pounds (approximately 90.7 kg), safe and sustainable weight loss should prioritize long-term health over rapid results. Rapid weight loss—typically defined as losing more than 2 pounds (0.9 kg) per week—is not recommended for adolescents, as it can interfere with growth, bone mineralization, hormonal development, and psychological well-being.

A medically appropriate goal is gradual weight loss of 0.5 to 1 pound (0.2–0.45 kg) per week, achieved through a combination of modest caloric deficit, balanced nutrition, and consistent physical activity. This equates to a daily energy deficit of roughly 250–500 kcal—enough to promote fat loss while preserving lean muscle mass and supporting ongoing physical and cognitive development.

Nutritionally, the focus should be on whole, minimally processed foods: lean proteins (e.g., chicken, fish, legumes, low-fat dairy), complex carbohydrates (e.g., oats, quinoa, sweet potatoes, vegetables), healthy fats (e.g., avocados, nuts, olive oil), and adequate fiber and hydration. Skipping meals, extreme restriction, or fad diets (e.g., ketogenic, juice cleanses) are discouraged due to risks of nutrient deficiencies, metabolic adaptation, disordered eating patterns, and rebound weight gain.

Physical activity should include at least 150 minutes per week of moderate-intensity aerobic exercise (e.g., brisk walking, cycling, swimming), complemented by strength training two or more days per week to maintain muscle mass and support metabolic health. Incorporating movement throughout the day—such as taking stairs, walking between classes, or limiting sedentary screen time—is also beneficial.

Behavioral strategies—including self-monitoring (e.g., food and activity journals), setting realistic short-term goals, practicing mindful eating, and seeking family or professional support—are evidence-based components of successful adolescent weight management. A pediatrician, registered dietitian, or adolescent medicine specialist can help tailor a plan that respects developmental needs, screens for underlying conditions (e.g., thyroid dysfunction, insulin resistance), and addresses psychosocial factors such as body image or stress-related eating.

Importantly, weight is only one marker of health. Improvements in blood pressure, insulin sensitivity, sleep quality, mood, and physical endurance often occur before significant scale changes—and these outcomes deserve equal recognition and encouragement.