The body needs energy to maintain body heat, to carry out metabolic activity, for physical work and for growth. The recommended calorie (energy) allowances are designed to ensure that infants and children have the required energy for proper growth and health and adults are able to maintain proper body weight and health. Energy needs are designed according to age, body size, extent of physical activity and is different for adults, children, pregnant women and nursing mothers. The intake of calories which enables the adult to maintain a predetermined level of weight and physical activity is considered to be the level of energy requirement.
Source of energy in Indian diets
The main sources of energy in Indian diets, which are predominantly plant food based, are carbohydrate, fat and protein. Carbohydrates are derived largely from cereals present in them and constitute 80% of the diet and provide 50-80% of daily energy intake. However energy contribution from diets varies widely. Those belonging to low income groups have only 5% fat in their diet whereas, affluent families derive as high as 30% of their dietary energy from fat. However, most families derive nearly 10-12% of energy from proteins. The recent scientific update recommends
- Less than 10% of total energy from simple sugars
- Between 55-75% of energy from carbohydrate (intake from whole grains and legumes, vegetables and fruits
Dietary fibre which forms an indigestible and important component of plant foods were never considered as sources of energy. Dietary fibre is now considered to be a source of energy used by the colonic cells and by the liver. The energy field of various foods has been calculated on the basis of their content of carbohydrates, proteins, fat and dietary fibre.
Required calorie (energy) assessment
The unit of energy which has been in use for a long time is kilocalories. Though some countries have now adopted Joule as the unit of energy. The recommended calorie requirement is now assessed according to calorie expenditure rather than energy intake. Energy is reserved in the body as fat and this fat is required to maintain energy even when on some days the intake is below expenditure. Calorie intake is not considered the right measurement of energy requirements as some people might have inadequate intake and others could have more than adequate intake. Individuals with poor intake can become malnourished and underweight and those with more calorie intake can become overweight.
The recommended dietary intake is therefore decided on the basis that it must maintain health, nourishment, steady weight and physical activity. Unlike proteins and vitamins there are no safe levels of requirements but rather average requirements according to specified weight and quantum of physical activity.
Methods used for calculating energy requirements
Over the years a number of methods have been used by the FAO/WHO/UNU Expert Consultations and some of which have been adopted by the ICMR Expert Group. Some of the methods used to arrive at the required energy levels are physical activity ratio (PAR) which is expressed as the ratio of the energy cost of an individual activity per minute to the cost of the basal metabolic rate (BMR) per minute. Later the FAO/WHO/UNU Expert Consultation used the individually calibrated heart rate monitoring (HRM) method, and Doubly Labelled Water (DLW) technique to arrive at energy requirements.
The HRM method measures Total Energy Expenditure (TEE) of healthy well-nourished individuals by calibrating relationship between the heart rate and oxygen consumption. The use of the Doubly Labelled Water (DLW is considered the most accurate technique for measuring TEE in free-living individuals. TEE measured by this method includes the basal metabolism, the metabolic response to food, thermoregulatory needs, physical activity costs, and the energy cost of synthesis of growing tissues.
Energy requirements for adults and children
Daily energy expenditure of adults depends on their occupational activity, sleep and non-occupational activity, each typically for eight hours in a day. The energy requirement of infants is calculated by the FAO/WHO/UNU Expert Consultations on the basis of DLW method, and to this estimate energy acquisition due to growth, is added to arrive at the total daily energy requirement. For children the TEE is calculated by DLW too or heart rate monitoring, and the energy needed for growth is added to this estimate. This method is not suitable for Indian children especially in rural areas as they are more active, weigh less as compared to their western counterparts, so ICMR has taken this into consideration to come to this estimate.
Energy requirement during pregnancy for Indian women
Additional energy is required during pregnancy and the increase depends on the pre-pregnancy body weight and pre-pregnancy BMR. There is an increase in BMR because of tissue deposited during pregnancy as protein and fat in the foetus and the mother. Additional energy requirement of Indian women during pregnancy have been computed on the basis of pregnancy weight gain of 10 kg and 12 kg in a woman with original weight of 55kg and average height of 151cms. Additional energy needed for tissue deposition will be 85 kcal, 280 kcal and 470 kcal during the first, second and third trimesters respectively if the body weight gain is 12 kg.
Energy requirement for nursing mothers
Energy cost of lactation is determined by the output of mother’s milk and its energy content. Milk output is determined by test feeding and weighing, and a correction of 5% is made in arriving at the milk output for the insensible water loss of the baby. The energy content of milk is based on the energy value of protein, fat and lactose of the milk. There is no change in TEE during lactation period over that in the non-pregnant period. Frequent sitting for breast feeding itself could be an adaptation for energy conservation. Daily additional energy requirement of a woman doing exclusive breast feeding during the first 6 months would be 600 kcal and for partial breast feeding during 7-12 months, it would be approximately 520 kcal.
Energy requirements of Indians at different ages
|Age Group||Category||Body Weights||Requirements|
|Man||Sedentary work||60 kg||2320||39|
|Moderate work||60 kg||2730||46|
|Heavy work||60 kg||3490||58|
|Woman||Sedentary work||55 kg||1900||35|
|Moderate work||55 kg||2230||41|
|Heavy work||55 kg||2850||52|
Rounded off to the nearest 10 kcal/d
GWG – Gestational Weight Gain
WG – Gestational Weight gain remaining after delivery
*Table Source: ICMR