Vitamins, energy use and Laboratory work 5

All processes in the body – metabolism, keeping warm, movement, heart and breathing, growth – need energy. Cells obtain it by breaking down nutrients; it turns into mechanical (muscle), electrical (nerve impulse) and heat energy, and part of the heat keeps body temperature. Energy is measured in kilocalories (kcal) or kilojoules (kJ) (1 kcal ≈ 4.2 kJ). The need for energy differs for each person with age, sex, growth, activity level and climate; a growing teenager needs not less food than an adult, often more, so there is no need to set yourself a “norm” or compare with others. Rules of healthy eating: varied food (protein, carbohydrate, fat, vitamins, minerals, fibre), 3–4 meals at set times, not skipping breakfast, sweets and fried or fatty dishes in moderation, enough vegetables, fruit and water. When food and activity are in balance through the day, body weight develops in its own healthy way. If you worry about body shape or weight, or feel drawn to strict dieting, talk to parents and a doctor; restricting food on your own or fasting is harmful. Every body has its own shape, and worth does not depend on weight but on health and kindness.