Nourishment for a newborn as well as a senior citizen revolves around the adequate intake of three macronutrients—proteins, carbohydrates and fats. All of the nine essential amino acids, unrefined and high-fibre sources and essential omega fats must come from the diet. Essential nutrients are those that cannot be produced by the body and therefore must be obtained from food alone. The forms (of the nutrients) and required quantities differ according to age.

Careful attention to nutrient intake and physical activity plays a significant role in determining not just life expectancy but also the quality of life and absence of disease across the lifespan. For instance, recommendations for controlling the intake of foods that are high in saturated fats begin as early as the age of 2. The build-up of atherosclerotic plaque within the arteries can begin early in life, and it has been documented that infants and children whose diet lacks in healthy nutrition tend to follow similar habits as they age. Also parents who are obese and sedentary for the most part of their life indirectly influence their children to adopt unhealthy eating practices and become obese themselves.

It is important to note that energy needs, and therefore nutrition needs, vary in accordance with the growth phases that are affected by age and gender. These phases are broadly infancy and early childhood, followed by adolescence, adulthood and old age. For the most part, macronutrients (protein, carbohydrate and fats), as well as micronutrients (vitamins, minerals and antioxidants) are always required throughout the lifespan. However the emphasis on calories, specific nutrients and water intake might require special attention as you grow older.

An active one-year-old requires about 1,000 calories a day, because of an enhanced growth rate. A two-year-old, however, requires just 300 calories more, and by the age of 10, a child needs 2,000 calories per day. In other words, energy needs increase to some extent, but the energy need per kilogram of body weight declines with age. This means that a one-year-old needs 100 calories per kilogram of body weight and a three-year-old needs 81.5 calories per kilogram of body weight.

With adolescents, the growth spurt begins at the ages of 10 and 11 for females and 12 or 13 for males and lasts up to two years prior to puberty. For females, body fat percentage increases, and for males, conversely, the percentage of lean tissue increases. Energy needs depend on individual rates of growth, gender, body composition and activity. A 15-year-old boy who typically gains more muscle tissue than a 15-year-old girl would require to eat at least 4,000 calories per day while the girl just 2,000 calories. The RDI (recommended daily intake) for most vitamins increases during adolescence and is similar to those for adults. During puberty, the absorption of calcium and vitamin D increases to strengthen bone structure, and as such the nutrient needs for these increases during this phase. The need for iron also increases during adolescence. For girls, more iron is required to facilitate the menstrual cycle and for males, iron supports the growth of muscle and lean tissue.

For adults, the average energy needs decline by approximately 5% every decade. This is because activity levels reduce sharply and this in turn results in a loss of body mass. Adults would do well to eliminate calorie-dense foods especially after the age of 50, and this is why an important emphasis in adulthood lies in choosing nutrient-dense foods. Protein food sources must be lower in calories and high in protein quality. Lean poultry, egg whites, skimmed-milk paneer (cottage cheese) are important for adults. Unrefined, coarse and high-fibre carbohydrate foods like wholegrain and legumes are nutrient-dense choices. Limiting saturated fats is important to control blood cholesterol levels as is the adequate intake of vitamin D and 1,200mg of calcium per day, especially for women.

Older adults need to take care especially of their water intake as total body water and the thirst response decreases with old age. Deficiencies of vitamins B12 and iron that could occur typically in later years might need supplementation under the guidance of a physician.

Madhuri Ruia is a nutritionist and Pilates expert. She runs InteGym in Mumbai, which advocates workouts with healthy diets.