Calories (energy) AND Management of Body Weight

caloriebodyweightEnergy is measured in calories. One unit of energy is one calorie. We continuously spend calories (energy) to run vital functions like breathing and circulating blood around. We obtain all our calories from the food we consume, and meet our energy requirement with these calories.


Just as weight is measured in grams and distance is measured in meters, energy is measured in calories.

The terms energy and calorie are used interchangeably in this chapter.

How are calories spent?

We constantly spend energy (calories) for vital functions such as respiration, digestion of food, production of urine, and maintenance of the blood circulation. This calorie expenditure is not under our control and will take place whether we want to or not. These calories will be spent whether we are active or totally sedentary. A very large portion of our daily calorie expenditure is through this route. The number of calories spent through this route depends on our body weight, height, gender and age, and is known as basal metabolic rate (BMR). The BMR can be calculated by a simple formula called the Mifflin St Jeor equation.

What are calories, energy, BMI, BMR?

What makes us gain weight?

Why is it so difficult to lose weight?

How to reduce body weight?

What is the relation between physical exercise and weight gain?

Mifflin St. Jeor Equation for calculating BMR

The BMR is the number of calories we spend performing vital bodily functions. There is no such thing as a normal BMR. It is different for every individual because the BMR is determined by the individual’s body weight, height, age and gender.

Men: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) + 5

Women: BMR = 10 x weight (kg) + 6.25 x height (cm) – 5 x age (years) –161

Evaluation of BMR is very useful in weight management research work because most of our daily energy expenditure is through this route.

Calories are also spent when we carry out any physical activity such as walking, exercising, talking and chewing food. This calorie expenditure is under our control. By increasing our physical activity we can increase our calorie expenditure, and decrease our calorie expenditure by reducing physical activity. For an average person with modest physical activity, not many calories are spent through physical activity.

Our total calorie expenditure each day = BMR calories + calories spent by physical activity.

An average person expends about 1800-2000 calories each day. The calorie expenditure by physical activity is pretty small – about 200-400 calories. Most of the calories are spent through the BMR route which is about 1500-1800 calories.


Whenever we gain weight, we generally attribute it to the lack of ‘morning walk’ over the preceding few weeks or months. Walking bestows great many health benefits, but has little impact on our weight. Our ability to burn calories by modest exercise (like walking) is pretty meagre compared with our potential ability to consume huge number of calories from food and beverages.

Food has a real, total and immediate effect on our body weight: we gain weight because we overeat and consume too many calories, particularly, simple and refined carbs, which have a direct influence on many hormones such as insulin.

Samosa (one) 200 19 minutes
Roasted peanuts (50 g) 300 28 minutes
Packet of potato chips 170 16 minutes
Cold drink (200 ml) 92 9 minutes

Source of calories (energy)

Our one and only source of energy is food. Every item of food and beverage has calories. Water is the only substance which has no calorie.

Calories obtained from FAT, PROTEIN and CARB (per gram)
Protein 4 calories
Fat 9 calories
Carb 4 calories

Our body processes whatever we eat, uses up the calories that are immediately required and stores the remaining energy. The excess calories from fat are stored as fat, carbs are stored as glycogen in the muscles and liver, and protein is stored in the muscles. We have an instant and perpetual access to this stored energy – we are continuously depositing and picking up calories from this store.

This system works very well to our advantage. Our intake of energy is irregular because we eat at uncertain intervals but we need a steady and continuous supply of energy. This requirement can be easily met from the stored fat, glycogen and protein.


An understanding of BMR is valuable because it is through this route that most of our calories are spent each day, and this plays a vital role in weight management:

1) An average person with modest physical activity spends about 1800 to 2000 calories each day. Most of these calories (1500-1800 calories) are spent through the BMR route. A small number of calories (200 to 300 calories) are expended by physical activity.

2) The BMR of a heavier person is higher compared with a lighter person. A heavier person spends more BMR calories every day.

3) In order to reduce body weight, it is vital that we eat fewer calories (less food) than what are spent. As the weight declines, BMR decreases proportionately, and consequently, fewer calories are spent. So, to maintain the process of weight reduction we have to gradually cut back on food to ensure that the total calorie intake continues to remain less than the calories spent.

The route to overweight and obesity

The biochemical and biological processes that govern our body weight are very complex and not fully understood. Nonetheless, it is now clear that excessive calorie intake, and too many carbs in the diet play a key role in producing overweight and obesity.

1. Excessive calorie (food and beverages) intake:

The state of calorie balance (calories intake vs calorie expenditure) absolutely determines our body weight. If we regularly consume more calories than what our body spends, we will gain weight and become overweight and obese. This solid law of nature holds true for whichever diet is consumed.

2. Too many carbs in the diet:

Although calorie balance is completely and totally responsible for what we weigh, excessive consumption of carbs also plays a very prominent role in producing overweight and obesity.


Calorie restriction (i.e. not overeating) has a positive effect on the lifespan of individuals. Studies suggest that this may be due oxidative stress suppression through the action of antioxidant superoxide dismutase.

Over the past few decades, fat in our diet has been so severely demonized that we have become wary, and have reduced fat to the bare minimum. Consequently, carbs are now form a dominant part of our diet, more than 60% of food consumed consists of carbs. The carbs are mostly simple and refined such as sugar, glucose, white rice, white bread and buns, noodles and pastas from refined flour, sweeteners such as high fructose corn syrup, and processed foods like corn flakes and pizza.

Under-estimation of food consumption

We under-estimate our total food and beverage consumption. When we try to assess the food we have eaten, it is quite common to consider only the things eaten at mealtimes, and ignore all the tidbits consumed such as biscuits, sweets, refreshments and sugary beverages. Every item of food and beverage delivers calories and these add to the calories consumed at mealtimes.

Excessive intake of refined carbs leads to overweight and obesity. This is how it works:

Excessive refined carbs in our diet leads to the secretion of large amounts of insulin. The refined carbs are rapidly broken down to glucose. Over the course of a few hours after a meal, the insulin helps the cells absorb glucose, and it also moves the circulating fat into fat cells. The large quantity of insulin ensures that most of the circulating fat is stored away in fat cells.

When most of the circulating fat gets stored away, very little is left in the blood for supplying energy. Our brain senses a shortage of energy, and sends out two signals: the first signal is to conserve energy, so the stored fat remains locked in the fat cells, which contributes to weight gain; the second signal is to acquire energy, causing the ‘hunger signal’ to be released. The hunger signal promotes food intake which inevitably means more carb consumption, and the whole cycle is repeated.
Regular consumption of large amount of carbs results in excessive secretion of insulin, fat storage, and increased food intake. The net result: overweight and obesity.

Once we become overweight, we are set on the path to steadily gain more weight. This is because overweight causes insulin resistance. The circulating insulin is unable to process the blood glucose. Our body responds by secreting progressively larger amounts of insulin to overcome the resistance to insulin. Because of the large amount of circulating insulin, there is a sustained storage of dietary fat in fat cells – leading to continuous weight gain.

If simple and refined carbs are eliminated from the diet, the situation changes completely. Studies have shown that a very low carbohydrate diet with no refined carbohydrates has a very favorable effect in reducing weight and maintaining this over time. In such a scenario, very little insulin is secreted, and all this insulin is used up to process the glucose in the blood. There is no excess insulin available to push the fat molecules into the fat cells, and the fat remains in the circulation to provide energy. There is a plentiful supply of energy so the brain does not send any signal to conserve the energy nor does it send any ‘hungry signal’. Net result: fat is not stored and there is no increased demand for food intake.

Why is it so difficult to lose weight?

Most of us who wish to shed weight do so by cutting back on food, primarily fatty food: we adopt a low calorie (i.e. less food), low-fat diet. We manage to lose a few kilograms but within a few months are back to where we started and some more.

There are three factors that make it difficult to lose weight:

a) After a few weeks of enthusiasm, we lose the passion and motivation for the low calorie (less food), low fat diet.

b) As the weight gradually decreases, the BMR also correspondingly declines, and our calorie expenditure progressively decreases. So, in order to continue losing weight, the intake of calories (food and beverages) has to be reduced gradually. This is difficult to implement.

c) A low fat diet is inevitably high in carbs. Any attempt to try to lose weight is doomed to failure when there is a surfeit of carbs in the diet. By severely restricting calorie intake we will manage to lose some weight for a while, but the powerful role of insulin will ensure that within a few weeks or months, we will not only have regained all the lost weight but will end up gaining some.


Our body weight is totally dependent on the balance between the calories we consume and the calories we spend each day. This is how calories work:

Losing body weight

If we eat fewer calories each day than our requirement, our body will break down stored fat to obtain the deficit calories. Regular consumption of fewer calories will lead to regular breakdown of fat and will result in reduction of weight.

For example, if we consume 1500 calories each day but require, say, 1800 calories, our body will automatically breakdown 33 grams fat to get the deficit 300 calories (each gram of fat produces 9 calories). If this calorie consumption and expenditure pattern continues unchanged, we will lose 1 Kg weight in a month.

Steady body weight

If we spend all the calories (energy) that we consume, we are in a balanced state. Our weight will remain unchanged.

Gaining body weight

On the other hand, if we regularly eat more calories than we burn, the excess calories will be stored as fat, we will gain weight, and become overweight and obese.

If we consume 2500 calories and use up only 2000 calories each day, there will be an excess of 500 calories in the system. These surplus calories will be converted mostly into fat (500 calories=55 grams fat) and stored in the body. If this eating and expenditure pattern remains unchanged, we will gain 1.6 Kg in a month.

A simple guide to reducing weight


caloriebodyweightFor an overweight and obese person, the whole reason for reducing weight is to achieve good health.

Weight can be reduced in the short term by ruthlessly cutting back on food intake which will guarantee fewer calories, but will also result in a severely reduced intake of vital micronutrients. This weight loss will therefore be associated with poor health outcome, and is not at all desirable.

The best way to reduce body weight and also ensure an abundance of health promoting nutrient intake is by eating in moderation, avoiding simple and refined carbs, and consuming a nutrient dense diet which includes dairy produce, eggs, meat, fish, whole grains, dal, fruits, vegetables, seeds and nuts.

Scientific studies have consistently shown that although a negative calorie balance (consuming fewer calorie than what are spent) is the only consideration that produces weight loss, there is another factor that also plays an important role. This is the quantity of carbs consumed, particularly simple and refined carbs. Cutting out simple and refined carbs helps lose weight without the need to focus on calorie intake. This is convenient because it is absolutely impossible for most of us to track our calorie consumption, but we can easily stop consuming certain groups of food such a simple and refined carbs. Modest physical activity has many health benefits, but does not have any significant influence on our weight.

Eliminating simple and refined carbs will inevitably mean that the diet will be high in fat and protein. When we eat, once the stomach is full, the fatrich diet will send out a message of satiety. This is the signal for us to stop eating. It is nature’s way of ensuring that we do not consume too many calories. Failure to heed the message of satiety, will result in overeating and weight gain, even with a low carb diet. Several hormones such as insulin, gherlin and leptin play a critical role here by establishing a calorie balance in favor of ideal body weight.

This weight reduction plan will be effective only if simple and refined carbs are truly discontinued. Unrefined whole grain carbs such as whole wheat products, brown rice, bajra, jowar, corn, sattu, ragi, and dal have a subdued effect on insulin and other hormones, and therefore, it is perfectly OK to consume them in moderation.

To assess weight accurately we should use a reliable, personal bathroom weighing scale. Public weighing scales are notoriously inaccurate because of improper calibration.

Besides reducing the body fat and body weight, a low carb diet confers many other advantages. A low carb diet reduces triglycerides (bad lipid), increases the ‘good’ HDL-cholesterol, and decreases the overall number of toxic small, dense LDL, the type that promotes heart disease. Saturated fats, part of a high fat diet, make the LDL particle size large. The net effect: reduced risk and reversal of heart disease

Moderation is a very subjective term. What is ‘moderate’ consumption to one person is inadequate or excessive to another. The way to assess whether our food intake is moderate, is to check our body weight regularly. If the weight is creeping up, we are consuming food (and calories) in excess.


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