Food, Nutrition, Health and Fitness

Written and reviewed by Anjali Sharma, Biology & Home Science faculty at UniDrill (M.Sc. Botany, Banaras Hindu University · 8 years teaching). Based on NCERT Home Science Class XI (Human Ecology and Family Sciences Part I), Chapter 3.

Why does a 15-year-old feel hungry all the time?

Between about 12 and 18 years your body grows faster than at almost any other time after infancy. Hormones drive a growth spurt that affects every organ, so your need for nutrients rises through childhood, peaks in adolescence and then levels off or even falls in adulthood. The saying "you are what you eat" is not a slogan here. It is the reason the school tiffin, the evening snack and the skipped breakfast matter so much. This chapter shows what food does for you, how to plan a balanced day of meals, and what goes wrong when teenagers diet, skip meals or live on fast food.

Four words that sound alike: food, nutrition, nutrients, health

Food does four jobs: it supplies energy, enables growth and repair of tissues and organs, protects the body from disease and regulates body functions. Most foods contain more than one nutrient. Milk, for example, has proteins and fats. Nutrition and health are "two sides of the same coin", so food is the most important single factor for health and fitness.

Macronutrients and micronutrients. The split is based on how much we need every day.

Health and fitness are not the same

Positive health is a blend of physical, social and mental well-being. Mental health is a state in which a person can use her cognitive and emotional abilities, function in society and meet everyday demands. Having no recognised mental disorder is not the same as having good mental health. Signs include feeling capable and competent, handling normal stress, keeping satisfying relationships, living independently and being able to "bounce back" after difficulty.

Physical fitness is good bodily health, and it is the result of regular exercise, proper diet and nutrition, and proper rest. It is the capacity of the heart, blood vessels, lungs and muscles to work at optimal efficiency. Earlier it meant carrying out the day's activities without undue fatigue. Automation, more leisure time and lifestyle change after the Industrial Revolution made that definition insufficient, so now optimum efficiency is the key. Fitness can be divided into five categories: aerobic fitness, muscular strength, muscular endurance, flexibility and body composition.

Two views. For the exam: health is complete physical, mental and social well-being, not merely the absence of disease. Another reading: some health scholars argue that "complete" well-being is an ideal that almost nobody has all the time, and suggest that health is better described as the ability to adapt and cope with challenges. For the exam, write the WHO form first.

Pause and predict: a cricketer can sprint 100 metres easily but is often anxious and lonely. Is she fit, healthy, both or neither?

Check your answer: She has physical fitness but not complete health, because health also includes mental and social well-being. This is the standard way to separate the two terms.

Balanced diet, requirement and RDA

A balanced diet includes a variety of foods in adequate amounts and correct proportions to meet the day's needs of all essential nutrients: proteins, carbohydrates, fats, vitamins, minerals, water and fibre. It also provides a safety margin or reserve that helps the body get through short spells of deprivation, such as fasting days or a few days of poor intake.

A balanced diet takes care of six aspects.

RDA versus requirement. A requirement is the amount of a nutrient that an individual actually needs. The Recommended Dietary Allowance (RDA) is the amount recommended to cover the needs of practically all healthy individuals. RDAs are guidelines on what to consume daily, not the requirement of any one person. The safety margin is already built in.

$$\text{RDA} = \text{Requirement} + \text{Margin of safety}$$

Worked example: RDA. For an illustrative nutrient, the average requirement of a group is 20 units a day and the margin of safety is 4 units. What is the RDA?

A common wrong step is to treat the RDA as the least amount a person needs. It is larger than the requirement because of the margin of safety. A diet that meets the RDA already contains the safety margin.

Energy from food: 4, 4, 9

Carbohydrates and proteins release 4 kcal per gram, and fats release 9 kcal per gram. This is why a spoon of ghee carries far more energy than a spoon of sugar.

$$\text{Energy (kcal)} = 4\times(\text{g carbohydrate}) + 4\times(\text{g protein}) + 9\times(\text{g fat})$$

Worked example: a tiffin snack. A snack contains 30 g carbohydrate, 10 g protein and 8 g fat. Find its energy and the percentage of energy that comes from fat.

The common wrong step is to use 4 kcal for fat as well. That would give $8 \times 4 = 32$ kcal and understate the energy of fat by more than half.

Worked example: the cereal limit. The guideline says cereals should not supply more than 75 per cent of total calories. A teenager eats a diet of 2,200 kcal, of which cereals supply 1,500 kcal. Is it within the limit?

Beyond the textbook. For the exam: carbohydrate 4, protein 4, fat 9 kcal per gram. In reality: alcohol also supplies energy, about 7 kcal per gram, and fibre supplies very little, which is why the three-number rule applies to the main food nutrients only. Why it matters: if a question mentions only the three macronutrients, the 4-4-9 rule is exactly what is wanted.

Five food groups for planning meals

A food group is a set of foods with common characteristics: the source, the function or the nutrients present. Grouping makes it easy to check that a day's meals have everything. The Indian Council of Medical Research suggests five groups for India. The grouping considers availability of food, cost, meal pattern and prevalent deficiency diseases. Not all foods in a group are equal, so variety within each group is needed.

Guidelines for using the food groups. Include at least one serving from each group in each meal and choose widely within each group. In vegetarian meals, use combinations such as cereal with pulse, or add a little milk or curd, to improve overall protein quality. Include raw vegetables and fruits, and at least one serving of milk, since milk contains all nutrients except iron, vitamin C and fibre. Cereals should not supply more than 75 per cent of total calories. Overall, take cereals and pulses adequately, fruits and vegetables liberally, animal foods moderately, and oils and sugars sparingly.

Worked example in a thali. A school lunch has two rotis, dal, a bowl of mixed vegetables, a bowl of curd and a pickle.

All five groups appear, though a seasonal fruit would make group IV stronger. This is how the group system is used to assess a meal.

Food guide pyramid

The food guide pyramid is a picture of the daily food guide. It shows variety, moderation and proportion. Cereals sit on the broad base, fruits and vegetables above, milk and meat in a smaller band, and fats, oils and sweets at the tiny apex.

About 75 per cent of a day's servings should come from grains, vegetables and fruits, which are plant foods. This provides complex carbohydrates, fibre, vitamins and minerals with little fat, and also makes planning easier for vegetarians. Foods in one group cannot replace those in another and no group is more important than another. The pyramid is a general guide and not a rigid prescription.

Vegetarian food guide. Vegetarians use the same food groups and the same number of servings. They can pick alternatives to meat such as legumes, seeds, nuts, tofu and, for those who eat them, eggs. Legumes and at least a cup of dark green leafy vegetables help to supply the iron that meat usually provides. People who do not drink cow's milk can use soy "milk" fortified with calcium, vitamin D and vitamin B12.

Beyond the textbook. For the exam: the daily food guide is shown as a pyramid with cereals at the base. In reality: many countries now present similar advice as a plate divided into portions instead of a pyramid, because a plate is closer to how people actually see their meals. Why it matters: the message is the same, so a plate-style picture in a question is still testing variety, proportion and moderation.

Adolescent eating patterns

Nutrient needs rise during puberty because of rapid growth and changes in body composition. Surveys of intake find that adolescents are likely to get less vitamin A, thiamine, iron and calcium than recommended, and more fat, sugar, protein and sodium than is optimal. Good habits now help prevent obesity, heart disease, cancer and diabetes later.

Fast food limitations. Fast food can contribute nutrients but cannot completely meet a teenager's needs. It is acceptable when taken judiciously as part of a balanced diet, but not as the mainstay.

Dieting. Obesity is a growing problem among adolescents, and if ideal weight is not maintained a large share stay overweight as adults, which raises the risk of diabetes, high blood pressure, high cholesterol and sleep apnea. But dieting by teens of normal weight, unsupervised by experts, can lead to dangerous outcomes. Symptoms include skipping meals, binge eating, fasting and using laxatives or diet pills. Cycles of weight loss and regain raise the chance of eating disorders and obesity and can lower self-esteem. One approach is to replace the word "diet" with healthy eating.

Pause and predict: Neha skips breakfast every day because she thinks it will help her lose weight. By mid-morning she is so hungry that she eats two packets of biscuits. What does the chapter say about her plan?

Check your answer: It is likely to do the opposite of what she wants. Skipping breakfast leads to overcompensating for the "saved" calories later, can slow metabolism and can contribute to weight gain and poor performance.

Changing diet related behaviour

Adolescence is a time when a person questions authority and tries to establish her own status, and eating behaviour is one of the ways individuality is expressed. Rejecting healthy home food and eating outside, sometimes to conform to peers, is not uncommon. The chapter offers practical suggestions.

Urban and rural adolescents. The picture is different in different settings.

Anaemia in adolescence. Anaemia means low iron in the blood. The survey NFHS-3 (2005-06) found that 56 per cent of adolescent girls were anaemic compared with 30 per cent of adolescent boys, and 70 per cent of children aged 6 to 59 months. The incidence had risen since the 1991-92 survey. It is high in developing countries because of poverty, inadequate diet, certain diseases, repeated pregnancy and lactation, and poor access to health services. Adolescence is an opportune time to act, because growth needs are high and girls need to improve iron status before pregnancy. Schools, recreation activities and the mass media can carry messages on iron-rich foods and iron supplements where needed.

Beyond the textbook. For the exam: anaemia is low iron in the blood, to be prevented with iron-rich foods. In reality: the body absorbs the iron from plant foods better when vitamin C is eaten along with it, for example lemon on a plate of dal or greens, while tea or coffee with meals reduces iron absorption. Why it matters: it explains why food combinations in a thali matter, and why advice on anaemia is about the whole meal, not a single food.

What influences adolescent eating behaviour?

Eating habits are shaped by many forces. The foundation is laid in the family, but many influences come from outside.

Adolescents buy and prepare more of their own food and often eat quickly and away from home. Parents should let them choose from a range of nourishing foods and give them freedom to use the kitchen, for boys as well as for girls. Peers can be a source of support or of stress. Advertisements, mostly for sweet and fatty products, influence teens, and the easy availability of ready food through home delivery, vending machines, melas, movie halls and sporting events makes more frequent and less healthy eating likely.

Eating disorders

Adolescence combines rapid growth and body-image development, so eating disorders are of special concern. Body-image distortion and low self-esteem are at their strongest when a person is still struggling with identity.

Both can cause convulsions, renal failure, irregular heartbeat and dental erosion. In adolescent girls anorexia can delay the onset of menstruation, permanently reduce stature and cause osteoporosis (weak bones). Prevention begins with valuing and respecting oneself. Dietary interventions include ensuring balanced diets, enhancing fibre intake and using nutrient or food supplements to make up for losses.

Exam traps

60-second revision

Where this chapter connects

• Previous: Understanding the Self explains body image, self-esteem and peer influence that drive the food choices here.
• Next: Management of Resources treats health as a key resource and shows how to manage time, energy and money.
• Later in the course: Nutrition, Health and Well-being builds on these basics.
• Class XII link: Public Nutrition and Health and Clinical Nutrition and Dietetics take the same ideas to communities and patients.